February, 2010

® DEMYSTIFYING EVERYDAY CHEMISTRY

FEBRUARY 2010

Chemistry in the Operating Room How Anesthetics Make Surgery Pain-Free, p. 8

Turning Plants into Green Gasoline, p. 13 What’s so Special about Mineral Makeup?, p. 16 QUESTION FROM THE CLASSROOM By Bob Becker

Reprinted from ChemMatters, December 2004. body weight would have a 50:50 chance of dying. A rat having only 13 mg of arsenic injected What is the most deadly poison in the world? p h otodisc intraperitoneally would have the Q same risk. If this can be applied to average (75 kg) humans, it would take 57,000 mg (57 g, about 2 oz) of ingested arsenic The answer to your ques- alone, and 4–5 million worldwide. 100% of the population). LD50 A tion depends on how No other poison even comes serves as a sort of average lethal to kill off an average human. As it you define “poison” and what close to these numbers. dose. It is important to point out turns out, compounds of arsenic you mean by “most deadly.” You Tobacco is a chronic poison; that these toxicity tests are not are considerably more lethal than might be tempted to define a poi- repeated exposure to it over the conducted on humans (obvi- the element itself. The ORL-RAT son as being any chemical that long term kills. If one decides ously), but instead on laboratory LD50 for diarsenic pentoxide can cause death, but this is prob- to ignore the actual death toll animals such as rats and rabbits. (As2O5) is only 8 mg/kg—mean- ably not a very good definition. caused by a poison and focus One could certainly question how ing that it would only take 600 It would have to include water, instead on its sheer potency, ethical such research is, or even mg (0.6 g, about half the mass of since drowning accounts for then we need to learn how acute how applicable it is to humans. a dollar bill) of ingested As2O5 to nearly 4,000 accidental deaths toxicity is measured. The most Who’s to say that a substance kill off a 75 kg human. each year in the United States, common method for identify- lethal to rats would necessarily As2O5 is toxic, but dioxin (often yet it is doubtful that anyone ing the toxicity of a substance have the same effect on humans? labeled the world’s most deadly poison) is about 400 times more would ever think of water as a is LD50, which stands for lethal Nevertheless, LD50 yields deadly. With an ORL-RAT LD poison, since we need to drink it dose–50%. The LD50 indicates valuable information, especially 50 for our very survival! Webster’s the mass of the poison per when it comes to making deci- of only 20 µg/kg, it would only defines poison as “a substance kilogram of sions about what compounds take about 1.5 mg (the mass of that through its chemical action to allow in a certain insecticide this “O” if you cut it out of this usually kills, injures, or impairs or building materials. It is magazine page) to kill an average an organism.” This definition also important to point out human. In comparison, the nerve gas VX has an absorption LD50 of rules out water but certainly that the LD50 of a substance includes a vast number of com- depends quite a bit on the 60 µg/kg. pounds for which human route of exposure: by inhala- Ricin, a protein found in cas- exposure, even at very low tion (breathing in), absorption tor beans that’s been associated levels, can be fatal. (through the skin or eyes), with recent acts and threats The words “most oral ingestion (swallowed), intra- of terror, has about the same deadly” are also open to venous (injected into the vein), toxicity level as dioxin. But all of interpretation. Does this intramuscular (injected into the these toxins would be consid- refer to the substance that muscle), subcutaneous (injected ered “lightweights” compared to is responsible for the most under the skin), or intraperitoneal the protein-based botulin toxin, deaths each year, or the sub- (injected inside the membrane produced by botulinum bacteria stance that requires the smallest that lines the interior wall of the and associated with botulism, the dose to cause death? If one is abdomen). most severe form of food poison- vision di g ital ing. It’s arguably the most deadly referring to the substance that body weight necessary to kill If one looks up the LD50 for causes the most deaths world- 50% of a given population. arsenic, for example, it is listed poison in the world. With an LD50 in the range of 5–50 ng/kg, it is wide each year, the poison would Because individuals in any popu- as ORL-RAT LD50 763 mg/kg nearly 1,000 times as toxic as have to be tobacco. It has been lation will have a range of toler- and IPR-RAT LD50 13 mg/kg. estimated that 500,000 people ance levels to any given toxin, This means that a rat ingesting dioxin. die each year of tobacco-related it would be difficult to quantify 763 mg (about 3/4 of a gram) illnesses in the United States LD100 (the dose that would kill of arsenic per kilogram of its

2 Chemmatters, FEBRUARY 2010 www.acs.org/chemmatters ®

Vol. 28, No. 1 february 2010

DEPARTMENTS Question from the Classroom 2 Battling Wildfires: By Bob Becker When Water Won’t Cut It 10 What is the most deadly poison in the world? By Sherry Karabin To put out wildfires, firefighters use a variety Did You Know? 4 of chemical solutions. Learn about how these solutions work. Scientists create the world’s smallest transistor; nitrogen oxides Natural Resources Conservation Service, Auburn, Ala. contribute significantly to the ozone hole. Green Gasoline: Fuel from Plants 13 Profiles in Chemistry: By Michael Schirber Chris Pollock, Chemistry Gasoline can be produced from plants, and even Graduate Student 18 plant leftovers. It is called green gasoline, it may By Dan Risch never run out, and it is good for the environment. Chris Pollock shares his passion for chemistry and explains how his research activities may lead to better drugs to treat cancer. cl e mson univ rsity

FEATURES mi ke ci e lsi ls k i The Many Colors of Blood 5

By Diana Lutz mi ke ci e lsi ls k i Blood can come in many colors. Blue, green, purple, it all depends on the The Makeup of Mineral Makeup 16 animal. Learn about the chemistry inside the blood that produces these different colors. By Jane Andrew Mineral makeup products are one of the hottest trends in cosmetics. Anesthesia: Chemistry in the Are they better for your skin than regular makeup? Operating Room 8 By Claudia M. Caruana TEACHERS! Thanks to drugs called anesthetics, surgery and find your complete other medical procedures are pain-free. How were teacher’s guide for this issue at these “miracle” drugs discovered and how do www.acs.org/chemmatters they work? istoc k

Production Team Education Division Subscriber Information the cautions contained in the text, or from not Patrice Pages, Editor Mary Kirchhoff, Director Prices to the United States, Canada, and following standard safe laboratory practices. Cornithia Harris, Art Director Terri Taylor, Assistant Director, K–12 Science Mexico: $14.00 per subscription. Inquire Therese Geraghty, Copy Editor about bulk, other foreign rates, and back All rights reserved. No part of this publica- Policy Board issues at ACS Office of Society Services, tion may be reproduced, stored in a retrieval Administrative Team Ingrid Montes, Chair, San Juan, Puerto Rico 1155 16th Street, NW, Washington, DC system, or transmitted in any form by any Marta Gmurczyk, Administrative Editor Barbara Sitzman, Tarzana, CA 20036; 800-227-5558 or 202-872-6067 means, now known or later developed, includ- Peter Isikoff, Administrative Associate Ami LeFevre, Skokie, IL fax. Information is also available online at ing but not limited to electronic, mechanical, Steve Long, Rogers, AR http://chemistry.org/education/ photocopying, recording, or otherwise, without Technical Review Mark Meszaros, Rochester, NY prior permission from the copyright owner. Seth Brown, University of Notre Dame The American Chemical Society assumes no Requests for permission should be directed in David Voss, Medina High School, Barker, NY ChemMatters (ISSN 0736–4687) is published responsibility for the statements and opinions writing to ChemMatters, American Chemical four times a year (Oct., Dec., Feb., and Apr.) advanced by contributors. Views expressed Society, 1155 16th St., NW, Washington, DC Teacher’s Guide by the American Chemical Society at 1155 are those of the authors and do not neces- 20036–4800; 202-833-7732 fax. William Bleam, Editor 16th St., NW, Washington, DC 20036–4800. sarily represent the official position of the Donald McKinney, Editor Periodicals postage paid at Washington, DC, American Chemical Society. The activities in Ed Escudero, Editor and additional mailing offices. POSTMASTER: ChemMatters are intended for high school Ronald Tempest, Editor Send address changes to ChemMatters students under the direct supervision of Susan Cooper, Content Reading Consultant Magazine, ACS Office of Society Services, teachers. The American Chemical Society David Olney, Puzzle Contributor 1155 16th Street, NW, Washington, DC 20036. cannot be responsible for any accidents or © Copyright 2010 injuries that may result from conducting the American Chemical Society activities without proper supervision, from not Canadian GST Reg. No. 127571347 Printed in the USA Cover photography by Mike CiesiElski and istock photos. specifically following directions, from ignoring

chemmatters, FEBRUARY 2010 3 DID YOU KNOW?...DID YOU KNOW?...

Metals and Nonmetals: Scientists Create the World’s Smallest Transistor that is, it becomes a conductor omputers and other materials to make small only when a small voltage is other electronic transistors. C applied to it. But if the graphene devices are made of Recently, a team of scientists sheet is small enough—about small components called led by Andre Geim, a physicist five times the size of an atom—it transistors. One of the at the University of Manchester, can behave like silicon at room main functions of a United Kingdom, has used a temperature. By creating such transistor is to switch a form of carbon called graphene small graphene sheets, Geim and current on and off. Most to make such a tiny transistor. colleagues were able to build the transistors are made of Graphene looks like chicken wire; it is made of carbon atoms smallest transistor ever made. silicon, a material that ant h ony f e rnand ez is neither a metal nor a arranged in hexagons. nonmetal, but something (a) A silicon transistor is turned off when a At relatively low temperatures, —Patrice Pages in between: It conducts negative voltage is applied to the control graphene behaves like silicon— gate. The electric field created by the electricity only if a small negative voltage blocks the flow of electrons voltage is applied to it. from the source to the drain. Silicon has been used Reaction Mechanisms: Nitrogen to make transistors Oxides Contribute Significantly to the since the 1960s. Over the years, scientists and Ozone Hole engineers have been zone (O ) is a explanation may come, making increasingly 3 chemical present at least in part, from smaller transistors to O in the atmosphere that the work of a team of build more powerful acts as a shield against scientists led by A. R. computers and to store harmful ultraviolet radia- Ravishankara, an atmo- more information in elec- NASA tion. Since the 1960s, spheric chemist at tronic devices. But, in a scientists discovered Ozone hole over Antarctica. the National Oceanic transistor that would be Blue and purple areas that chemicals called and Atmospheric about 50 times the size (b) A silicon transistor is turned on when a represent low ozone levels. chlorofluorocarbons Administration, of an atom, silicon would positive voltage is applied to the control gate. The positive voltage reduces the electric field, (CFCs) and hydrochlorofluoro- Boulder, Colo. The scientists have oxidize and decompose. allowing electrons to flow from the source to carbons (HCFCs) destroyed the shown that nitric oxide (NO) and So, scientists are using the drain (white arrow). ozone above Antarctica, creating nitrous oxide (N2O) destroy more Source the so-called “ozone hole.” ozone in the atmosphere than Gate During the 1960s, 1970s, and CFCs and HCFCs. 1980s, CFCs and HCFCs were Although nitric oxide and widely used to make cleaning nitrous oxide were previously Drain solvents, refrigerants (chemicals known to destroy ozone in the found in refrigerators and air atmosphere, scientists had not Channel conditioners), and pesticides. compared its effects to those Starting in 1987, their emis- of CFCs and HCFCs. “Limiting sions have been sharply reduced future emissions of these two thanks to a worldwide agreement chemicals could enhance the Source-drain voltage called the Montreal Protocol. recovery of the ozone layer,” But the ozone hole is not gone Ravishankara says. entirely. Every year, in October, (c) The smallest transistor ever made consists of a material called graphene, the ozone hole reappears. The —Patrice Pages A nt h ony Fe rnand ez ;A dapt e d from “B y e- by silicon ,” J o r g H b , New Scie n ti s t De c 6, 2008. which looks like chicken wire.

4 Chemmatters, FEBRUARY 2010 www.acs.org/chemmatters The Many Colors of B ood

By Diana Lutz

Have you ever seen blue blood? How about purple, green, istock or even colorless blood? This is no science fiction. A respiratory pigment binds to oxygen and Here on Earth, the blood of carries it around the body, keeping organs and many animals can have . pbs or g tissues oxygenated. When a pigment molecule www one of these colors. The blue blood of horseshoe crabs contains a binds to an oxygen molecule, it absorbs a chemical that immediately tells whether a drug certain color of light, and we see whatever orseshoe crabs in a touch tank is contaminated with bacteria. Up to 30% of a light has not been absorbed. As a result, the at a North Carolina aquarium in crab’s blood is extracted and stored in bottles, here at a laboratory of Charles River Laboratories pigment molecules have different colors, and Pine Knoll Shores were getting International, Inc., in Charleston, S.C. so does the blood that contains them. sick. The crabs, which look like crawling samurai helmets, had infected sores spiders, and octopuses have blue inH their shells and were having trouble with blood. Certain bottom-dwelling their seven eyes. To find out what was wrong, marine worms have green blood. veterinarian Michael Stoskopf took a blood Sea squirts have purple blood. sample. And a few rare animals have When he looked at the blood under a micro- blood that is completely color- scope, Stoskopf saw that it was swarming less. So what is the reason for all with cells from the crabs’ immune system, of these different colors of blood indicating that these cells were fighting the in animals? infection. Stoskopf also noticed that scrapings from the crabs’ sores blossomed into bacte- Red blood rial colonies. This helped the veterinarian pick

versus c e sar camin ro the right antibiotic for the crabs’ infection. Once on this drug, the crabs perked right up, blue blood Figure 1. Structure of hemoglobin. Each of the four their sores healed, and they were soon lum- The blood of a horseshoe subunits (brown, orange, purple, bering about the tank. crab is blue because of a mol- and pink) contains a heme The blood Stoskopf drew into his syringe molecule (inset) with an iron ecule called a respiratory pig- atom in the middle. Blue sphere, was milky blue, but Stoskopf knew that ment. In humans, this molecule oxygen molecule (02). this was not a sign of sickness: The blood contains iron, while the crab of horseshoe crabs is normally blue. Many version contains copper, and animals have red blood, but crabs, lobsters, that affects the color of blood.

chemmatters, FEBRUARY 2010 5 But there is at least one family of animals NH NH H like this: the crocodile ice fish, sometimes H N N HN N called the bloodless fish, which live in the cold N N O2

, N. C. Cu(I) Cu(II) N waters surrounding Antarctica.

. M arin e L ab ., N ic h olas N N Cu(II) The blood of these fish is white and looks N Cu(I) N ., Be aufort NH N like cream when it clots. Ice fish manage with- N N N N N NH N H out a respiratory pigment because their blood H H HN HN does not carry oxygen very well, so they have

A nt h ony f e rnand ez; bas d on dia g ram from Kar e n M a g nus , D u ke U niv S c h ool of t he Env more blood than any other fish. Also, water in Figure 2. Structure of a hemocyanin molecule’s binding site before and after an oxygen molecule (O2) the Southern Atlantic contains more oxygen binds to the copper atoms in the middle. than warmer water, because more oxygen dissolves in cold water than in warm water. Another reason these ice fish get by without The human version of the respira- and the oxy- a respiratory protein is that they are relatively tory pigment is called hemo- gen molecule inactive and slow moving, so they need less globin, and the crab version becomes the ion oxygen than active fish. 2- is called hemocyanin. In peroxide (O2 ). hemoglobin, when iron binds The cuprous ion to oxygen, it absorbs mostly does not absorb visible Green blood blue light, so it appears bright light, making the blood of All animals with a backbone—also called red. In hemocyanin, when cop- a horseshoe crab that is not vertebrates—have red blood, except for a type per binds to oxygen, it absorbs oxygenated appear colorless. of lizard called the green-blooded skink. It istock mostly red light and thus Horseshoe crab Cupric ions, on the other hand, strongly lives in New Guinea, an island north of Austra- appears blue. absorb red light. With the red component lia that is home to some of the world’s most Hemoglobin is made of four proteins, each of light absorbed, these ions look blue, which unusual creatures, but none more unusual containing a large molecule called a heme explains why the oxygenated blood of a horse- than this armor-plated lizard. Its blood, which (Fig. 1). The iron atom is in the middle of shoe crab is blue. is lime-green, colors all of its tissues in green, the heme. By comparison, hemocyanin in a The atoms that bind oxygen in respiratory including its bones, tongue, and the lining of horseshoe crab contains a whopping 96 pairs pigments, such as iron and copper, are always its mouth. of copper atoms that bind to one oxygen transition elements, that is, elements that molecule each. One of hemocyanin’s bind- belong to groups 3 through 12 in the periodic ing sites (with one pair of copper atoms) is table. The reason is that oxygen interacts shown in Fig. 2. strongly with atoms or ions if it receives Hemoglobin and hemocyanin differ in size, electrons from them. Because transition metal too. Hemocyanin is bigger than hemoglobin. It ions give up or take back electrons easily, they binds to 96 oxygen molecules, far more than can bind to oxygen easily and let go of it just the measly four bound by hemoglobin. Also, as easily. e c h ris austin , louisiana stat univ e rsity The green tree skink (Prasinohaema virens) the hemocyanin molecules float free in the is one of five described species of green- blood, whereas millions of the smaller hemo- Clear blood blooded lizards from New Guinea. globin molecules are packed into cells called red blood cells. The respiratory pigments are so important Why is the blood of this lizard green? Like When a respiratory pigment is bound to that when scientists heard of creatures that people, skinks have red blood cells full of oxygen, it has a different color from when it did not have any, they thought it was a hoax. hemoglobin. In humans as well as in skinks, is not bound to oxygen. In hemoglobin, when red blood cells have short life- iron atoms are not bound to oxygen, they times, so they are then taken appear dull red. But when iron atoms bind to out of circulation by the liver. oxygen, the entire heme group folds in such a When these cells are trashed, way that it goes from a domed shape to a flat their hemoglobin is recycled. shape, which changes its color from dull red But this recycling process dif- to bright red. fers in humans and in skinks. In hemocyanin, when copper atoms are not In people, hemoglobin is bound to oxygen, they have each donated an recycled to form biliverdin, a electron to surrounding atoms and are called green chemical. Biliverdin is cuprous ions (Cu+). When an oxygen molecule then rapidly converted into a binds to a pair of copper atoms, each atom in yellow chemical called bilirubin. the pair gives up one electron to the oxygen Bilirubin is a toxic compound, U w e k ils molecule, resulting in two cupric ions (Cu2+), An ice fish off the coast of Antarctica is seen from below. so the liver filters it from the

6 Chemmatters, FEBRUARY 2010 www.acs.org/chemmatters BLOOD COLOR ANIMAL WHY THIS COLOR?

Red Humans Hemoglobin contains iron that binds to oxygen, making blood appear red.

Blue Horseshoe crab, Hemocyanin contains copper that binds octopus, lobster, spider to oxygen, making the blood appear blue.

Green Earthworm, leeches Chlorocruorin contains iron that binds istoc k to oxygen, making the blood appear green. “Tyrosinase, or a similar molecule, prob- Green Skink (type of lizard), Recycling of hemoglobin stuck halfway; ably protected these early organisms,” Decker marine worms biliverdin (green) accumulates in the says. “It probably took up the oxygen and body. incorporated it in molecules, such as melanin, Violet Lamp shells Hemerythrin contains iron that binds that the organisms needed.” to oxygen, making blood appear violet- After the Oxygen Catastrophe, some organ- pink. isms died and others adapted to the presence Clear Ice fish Blood does not contain a respiratory of oxygen. The organisms that survived ben- protein. efited from the enormous amount of energy generated by processing oxygen in their bod- The different colors of blood in animals ies. Over time, the oxygen-binding tyrosinase probably evolved into the oxygen-transporting blood as quickly as possible. If bilirubin builds hemocyanin. up to high levels, the skin becomes yellow—a Perhaps the many colors of today’s respira- condition called jaundice, which can be fatal. tory pigments are really the colors of despera- In skinks, the hemoglobin’s disposal pro- tion. Hardpressed by the Oxygen Catastrophe, cess is stuck halfway. Skinks cannot convert nature may have churned through many biliverdin into bilirubin, so biliverdin builds up solutions and found more than one key for the in the blood. There is so much biliverdin in same lock (the lock being the ability to carry a skink’s blood that even though the blood’s oxygen in the blood, and the keys being the respiratory pigment is red, the green color different respiratory pigments). swamps the red color, and the blood appears “Our studies have shown that evolution has green. The amount of biliverdin is 40 times apparently come up with several independent higher than the highest level ever measured in mi ke ci e lsi ls k i ways to transport oxygen, and this happened a human being. nin is closely related to a protein called tyrosi- at least four times,” van Holde says. “This is nase. This protein now plays a role in making typically how evolution works—not following Where do respiratory melanin, the pigment that colors human hair some design, but making seemingly random and skin. changes in proteins and then retaining what- pigments come from? The scientists believe that the similarity ever stands the test of natural selection.” Red blood, blue blood, green blood—Why between hemocyanin and tyrosinase is not are there are so many different respiratory accidental. They suggest that tyrosinase pigments? In the case of hemocyanin, the appeared on Earth about 2.4 billion years ago. Selected references answer may lie in an ancient protein At that time, the amount of oxygen in Carroll, S. The Making of the Fittest; W. W. Norton: New York, 2006. called tyrosinase. the atmosphere started to increase The Horseshoe Crab: www.horseshoecrab.org Kensal van Holde, emeritus dramatically—an event called [Aug 2009] professor of biochemistry the Oxygen Catastrophe. For Spelman, L. H.; Mashima, T. Y. The Rhino with and biophysics at Oregon the microscopic organisms Glue-on Shoes and Other Surprising True State University in Stories of Zoo Vets and their Patients; Random that had evolved before House: New York, 2008. Corvallis, and Heinz that time, oxygen was Perkins, S. The Iron Record of Earth’s Oxygen. Decker, a professor of essentially a poison: Science News, June 20, 2009, 175 (13), p 24. molecular biophys- These organisms did ics at the Johannes not need oxygen; in Gutenberg University, fact, being exposed to Diana Lutz is a science writer in Madison, Wis. Her most recent article, “Hollywood’s Special Effects: Mainz, Germany, have oxygen would have istoc k How Did They Do That?” appeared in the December shown that hemocya- killed them. 2009 issue of ChemMatters.

chemmatters, FEBRUARY 2010 7 ANESTHESIA Chemistry in the Operating Room

hroughout history, people have By Claudia M. Caruana can even be taken orally to relieve throat pain sought ways to relieve suffering. or canker sores. Many substances that control pain General anesthetics are used during medi- were found serendipitously, some- cal and surgical procedures that would be Ttimes by trial and error. As early as 4200 B.C., too painful to endure while awake. In addition people discovered natural substances—often to suppressing pain, as local anesthetics do, plants and plant roots—that could cause Until the mid-1800s, general anesthetics also induce a loss of con- unconsciousness in animals and people, so undergoing surgery was sciousness that may feel like deep sleep. But they used them to relieve pain. excruciatingly painful unlike sleep, in which parts of the brain work But it is only during the first half of the 19th because people would be by forming dreams and processing informa- century that people started testing chemical awake during the opera- tion, this loss of consciousness does not form substances on patients for their use in medical tion. Thanks to drugs dreams nor does it store memories. surgery. Over the years, various substances called anesthetics, all this Over the past centuries, people searched were identified, and their effectiveness was pain and suffering is gone. far and wide for substances with anesthetic compared. This work has led to an array of How were these “miracle” properties. A substance that would shut down medicines that can numb pain locally or cause drugs discovered and how the entire body was the most sought-after unconsciousness and decrease pain over the do they work? type of anesthetic. The pain from surgery entire body. and other medical procedures was often Scientists and health professionals now to numb the eye before certain eye examina- more excruciating than that from the local have a good understanding of which anesthet- tions—typically, when eye doctors measure treatment of a wound or a dental procedure. ics work best on patients, but they are still eye pressure or remove stitches or foreign So, medical personnel tested many differ- trying to uncover how these drugs operate at objects from the eye. ent substances on patients, sometimes with the cellular and molecular level. Other local anesthetics are available as oint- unexpected side effects. ments, sprays, or lotions to relieve itching, Local and general sunburn, insect bites, and minor cuts. They Nitrous oxide anesthetics One of the most well-known and Anesthetics can be applied either most successful general anesthetics to one area of the body—such as the is nitrous oxide (N2O). It was discov- skin, teeth and gums, or the spinal ered at the end of the 18th century cord—or to the entire body. These and is still being used in surgical two types of anesthetics, called local anesthesia. and general anesthetics, work by Nitrous oxide is a colorless, preventing nerves from carrying pain almost odorless gas that was first signals to the brain. This way, the discovered in 1793 by an English brain does not perceive pain. scientist and clergyman named Local anesthetics can be given Joseph Priestley. Following Priest- by injection to numb parts of the ley’s discovery, British chemist Humphry Davy realized that nitrous all p h otos from istoc k body during surgery and dental procedures. They can also be used oxide had physiological effects. He

8 Chemmatters, FEBRUARY 2010 www.acs.org/chemmatters noticed that people who inhaled it started medicine for shock therapy, but this practice cells, preventing them from carrying the pain laughing for no reason, and he called it has been discontinued. signal to the brain. “laughing gas.” The way general anesthetics work is even Davy realized the anesthetic effect of the It’s all in the chemistry more mysterious. Not only do these anesthet- gas, but for the next 40 years, the main use of ics prevent pain signals from reaching the nitrous oxide was in traveling medicine shows So, how do anesthetics work? When a pain- brain, but they also cause unconsciousness and carnivals. People would pay for inhaling ful sensation occurs—due to, say, a wound or and memory loss. Scientists hope to find small amounts of the gas and would laugh a teething pain—nerve cells send a message answers by comparing what happens at the and act silly until the effect of the drug wore cellular level during general anesthesia, actual off. Nitrous oxide found a more scientific use loss of consciousness (say, due to a stroke) as an anesthetic in dentistry and medicine in and amnesia (a medical condition that causes the early 1840s. memory loss). “It’s still a black box,” says John Stork, Other general a pediatric anesthesiologist at Babies and Children’s Hospitals, Cleveland, Ohio, and a anesthetics professor of anesthesiology at Case Western Nitrous oxide is still used as a general Reserve Medical College in Cleveland. “But anesthetic in combination with other chemi- there is considerable research going on to cals. But its main use is as a mild sedative help anesthesiologists understand how anes- and a pain reliever, because nitrous oxide can istoc k thetics affect the body at the cellular level.” cause the lungs to collapse and can lower the of pain to the brain. This message is car- General anesthetics also cause side oxygen content of tissues. ried by small electrical currents through effects, such as nausea and pain, so doctors Most of the other general anesthetics adjacent nerve cells. For these currents to provide antinausea drugs and painkillers to used today are administered through flow from one nerve cell to the next, the nerve patients. But how these side effects happen the lungs and thus are called inhala- cells exchange ions, such as sodium ions is not well understood. What physicians tion anesthetics. The first widely used (Na+). A nerve cell will release these ions— know is that during surgery, stomach acids inhalation anesthetic was diethyl ether through openings on the cell surface—and build up because of the many drugs given. (C2H5OC2H5), a highly flammable liquid, another nerve cell will capture them. Then, Physicians and scientists are investigating especially in the presence of oxygen. this nerve cell will do the same with what this build-up of stomach acids does istoc k Diethyl ether increases the risk of fires, another nerve cell, and so on. to the body; they are also looking at other or even explosions, in operating changes in the body that could cause nausea and pain. rooms during surgeries, so this F CI F H H H H compound has fallen out of favor. Anesthesia has relieved surgery Today, halogenated ethers have F C C O C H H C C O C C H patients from all the pain and suf- replaced most other compounds fering that they would feel other- F H F H H H H for use as inhalation anesthetic. wise during surgical procedures. An ether is an organic molecule Isoflurane Diethyl ether The next step will be for scientists that contains an oxygen atom to unravel the details of how anes- connected to two organic groups. F F F F thetics work at the cellular level CF3 Its general formula is R-O-R’, and to find ways to prevent their F C C O C H H C O C H where R and R’ are the organic side effects from happening. CF groups. A halogenated ether is F H F 3 H an ether in which one or more Desflurane Sevoflurane hydrogen atoms are replaced with halogen atoms (fluorine, chlorine, Selected references bromine, or iodine). Anesthetics work by preventing sodium Fradin, D. B. We Have Conquered Pain: The Examples of halogenated ethers include ions from going from one nerve cell to the Discovery of Anesthesia. New York: Margaret K. isoflurane (CF3CHClOCHF2), desflurane next. But the details of how this is done are McElderry Books, Simon & Schuster Children’s Publishing Division, 1996. (CF3CHFOCHF2), and sevoflurane (CF3CHC- not well known. An easy explanation would be Galas, J. C. Anesthetics: Surgery without Pain: The F3OCH2F). Halogenated ethers have the that the anesthetic molecules bind to a nerve Encyclopedia of Discovery and Invention. San advantage of being nonflammable and less cell and block the openings through which Diego: Lucent Books, 1992. toxic than earlier general anesthetics. the sodium ions are released. But this is not Shapiro, I. The Gift of Magic Sleep: Early But not all halogenated ethers have an what happens. Experiments in Anesthesia. New York: Coward, McCann & Geoghegan, 1979. anesthetic effect. For example, flurothyl Scientists have observed that the anes- (CF3CH2OCH2CF3) has the opposite effect, by thetic molecules do not bind to nerve cells, so Claudia M. Caruana is a medical and science inducing convulsions and epileptic seizures. the sodium ions are released. But somehow, writer who lives in New York, N.Y. This is her first Flurothyl was previously used in psychiatric these ions are not captured by other nerve article in ChemMatters.

chemmatters, FEBRUARY 2010 9 Battling Wildfires When Water Won’t Cut It By Sherry Karabin

An air tanker drops 2,450 gallons of fire retardant in northern Idaho. Lou Gildemeister

hey are a sight to behold and to Putting out fires tists and engineers working for the U.S. Forest fear at the same time—out-of- A fire occurs when three ingredients are Service, Washington, D.C., along with testing control raging wildfires. These present: oxygen (from the air), heat, and fuel. laboratories and private companies. blazes can ignite without warning, In the case of a wildfire, the fuel is vegetation Wildfires can be put out either directly or destroying forests, homes, and (plants and trees). These three ingredients indirectly. A direct attack consists of apply- farmland and taking lives, some- can be explained by using a diagram called a ing chemical solutions directly on the flames. times those of the firefighters themselves. fire triangle. These solutions contain more than 95% of To put out wildfires, firefighters use a water and less than 5% of gels or foams. variety of chemical solutions. These solu- An indirect attack involves preparing a tions are either dropped from an airplane or a “firebreak,” which consists of removing flam- helicopter or sprayed from the ground toward HEAT mable vegetation with bulldozers and shovels the fire. The chemicals in these solutions have or coating it with chemicals at some distance OXYGEN changed over time, but they all serve the same FUEL from an advancing fire front. The chemicals purpose: to prevent the flames from spreading Fire triangle used in an indirect attack react with the veg- etation so that it does not burn easily. and to contain and control the fire. The fire triangle shows that a “Firefighters are better equipped and wildfire can be prevented or extin- protected today than they were three or four guished in one of three ways: Direct attack of decades ago,” says Lou Gildemeister, a 1. Maintain a temperature below former fire control officer for the state of the fuel’s ignition point (the wildfires Montana and a senior technical service temperature at which vegeta- To battle flames directly, firefighters use tion starts burning). representative at the chemical company ICL very large quantities of water, along with Performance Products LP, Ontario, Calif. He 2. Minimize the amount of oxygen solutions that contain foams and gels. The surrounding the vegetation. recalls fighting a blaze in 1969 in Marysville, foams are made of water, air bubbles, and Mont., with a five-gallon backpack pump filled 3. Remove the vegetation. chemicals called surfactants that allow the with water. foam to expand and hold water. Gels are jelly- Nowadays, the chemical solutions used by The chemical solutions that have been devel- like materials made of polymers arranged like firefighters still contain water, but the added oped during the past five decades achieve one a honeycomb in water. Gels are essentially chemicals make all the difference in battling or more of these goals. All of the solutions that thickened water, and their consistency varies the flames faster and more efficiently. are currently used have been tested by scien- between that of cream and gelatin. istoc k 10 Chemmatters, FEBRUARY 2010 www.acs.org/chemmatters The effectiveness of solutions containing ions repel each other along the polymer In the 1960s, scientists and engineers foams and gels depends upon the amount chain, which widens the two polymer coils developed “long-term” fire retardants, so of water present. When water evaporates in and allows water to be in contact with the called because they remained effective even these solutions, they are no longer effective. carboxyl ions. after the water from the solution had evapo- It takes longer for water to evaporate in these As the polymer continues to uncoil, it rated. Long-term retardants are now com- solutions than in solutions containing only swells and acquires the consistency of either monly used by firefighters because they water. thickened water or gel, depending on the are effective and cause no known dam- A foam-containing solution can penetrate concentration of the powder. These gels often age to the environment. inside plants better than water, as this When fire retardants are solution sticks better to the surface of sprayed on vegetation, chemicals plants—say, on the leaves. This keeps in the fire retardants react with the the surface of plants cooler for a lon- main plant material, called ger period of time. cellulose, and prevent it Two types of foams are available. from burning. Cellulose is Class A foams are used to put out an organic molecule that con- wildfires, while Class B foams are used tains thousands of the against flammable liquids. These two same small molecule types of foam have a very low “surface C6H10O5, hence tension”—the force that holds mol- the formula ecules in a liquid together. (C6H10O5)n, If only water is sprayed on vegetation, where n is an

the water molecules are more attracted Se rvic e, A uburn , la . Re sourc e s C ons rvation N atural integer. When to one another than to the surface of a Vegetation is burnt by firefighters to create a gap in vegetation in the cellulose path of a wildfire in order to slow or stop the progress of the wildfire. plant, so they do not penetrate the sur- burns, it face easily. But solutions containing Class decomposes A foams have a lower surface tension, so they absorb as much as 400-800 times their mass into flammable gases and tars, such as penetrate into the plant’s surface more readily. in water. This thick layer of water has the methane, alcohols, and ketones. But when a The low surface tension of a Class A foam advantage of protecting the surface of a flam- plant that is bound to a long-term retardant solution is due to the presence of surfactants, mable material, such as vegetation exposed is heated, it does not produce these flam- chemicals that are used in very small amounts to flames. This protection lasts until all of the mable gases or tars. solution has evaporated. Most of the currently used long-term retardants contain ammonium phosphates, Indirect attack of which are either monoammonium phosphate [(NH4)H2PO4], diammonium phosphate wildfires [(NH4)2HPO4], or mixtures of various types The first chemical solutions developed as an of phosphates. When these phosphates are alternative to water contained substances heated, they decompose into ammonia (NH3) called fire retardants that make things harder and phosphoric acid (H3PO4). (a) (b) to burn. In the 1950s, the U.S. Forest Service The ammonia escapes as a gas, mi ke ci e lsi ls k i and the California Department of Forestry and and the phosphoric acid reacts with (a) A drop of water on a leaf does not spread cellulose through a series of chemi- on the leaf’s surface because of a force called Fire Protection in Sacramento worked together surface tension (see sidebar); instead, a solution to develop such chemical solutions. cal reactions that form phosphate of water and foam (b) spreads throughout the leaf The first fire retardant that was used in esters. Esters are molecules with and prevents it from burning in the presence of the general formula RCOOR', where flames. large quantities against wildfires was sodium calcium borate (NaCaB5O9). It melted on veg- R and R' are organic groups. Phos- in water (between 0.1% and 1% in volume) etation and enclosed it so that oxygen from phate esters are molecules with the general and allow the solution to dissolve more easily. the air could not reach it. In the 1950s, the formula OP(OR)m(OH)3-m ,where Unlike foams, gels consist of a network of “borate bomber,” an aircraft fitted with tanks R is an organic group and m=1, polymers in the shape of a honeycomb. In filled with sodium calcium borate, became a 2, or 3. the absence of water, these polymers have household name in the western United States, As heating continues, these the consistency of powder. The polymer mol- where most of the large wildfires occur. esters decompose to form water and ecules in this powder are coiled and lined with But sodium calcium borate prevented a non-flammable material called graph- carboxyl groups (–COOH ). vegetation from growing again, and new seed- ite, a form of carbon found in pencil lead. But when this powder is added to water— lings did not survive on soil that contained Also, the evaporated ammonia and water usually at concentrations of 0.5%–3%—the this chemical. As a result, the use of sodium vapor cool the fire. The phosphoric acid acts carboxyl groups dissociate into negatively calcium borate was discontinued between as a catalyst, that is, it remains behind after charged carboxylate ions (–COO–). These 1950 and 1955. the water and graphite are formed. Graphite istoc k

chemmatters, FEBRUARY 2010 11 Effect of Surfactants on Surface Tension

(a) At the surface of a drop of water, the water molecules can form hydrogen bonds (dashed lines) MI KE CI E SI LS K I with the molecules beneath and beside them but not with the molecules in the air above them. So, the water molecules on the surface are drawn inward. This inward force is called a surface tension. For example, ICL Performance Products is working closely with federal and state agencies, volunteers, and municipal fire departments to improve and increase the per- formance of firefighting chemicals. Their main goals are to provide more effective retardants, foams, and gels and to increase the safety of the public, firefighters, and the environment. In view of the advances that have been made in the past 50 years, it is hard to (b) Surfactant molecules (on the surface) have a part that likes water (circle) and a part that does imagine what more can be accomplished. not like water (tail). As a result, the tails of these molecules stick out into the air. The water But researchers probably thought the same molecules on the surface are attracted to the surfactant molecules, resulting in a net reduction of the overall force that pulls the water molecules inward. This allows the drop of water to sag thing 50 years ago. One of the most recent under the influence of gravity. advances includes a unit, called a Modular Aerial Fire Fighting System, which can be rap- idly installed in a C-130 National Guard cargo aircraft during a fire emergency. The C-130 aircraft can deliver 3,000 gallons of retardant. In the summer of 2009, a Boeing 747 fitted with a retardant tank was used to fight the ANTHONY FERNANDEZ Oak Glen fire, east of Los Angeles. It delivered (c) When more surfactant molecules are added, the drop of water spreads further on the surface. more than 20,000 gallons of retardant! Although Gildemeister, the firefighting spe- cialist from ICL Performance Products, no lon- ger fights fires personally, he sees a brighter future for those who do. Says Gildemeister, “With new technology being developed, the does not burn in atmospheric conditions, so it Retardants have been critical in recent safety of firefighters is bound to improve.” does not provide fuel to the fire. wildfires. In February 2009, more than 400 Thickening agents and color pigments fires erupted in southeastern Australia, and are also added to long-term fire retardants. the state of Victoria experienced extensive Without these agents and pigments, a solu- damage. The wildfires killed more than 175 Selected references tion containing long-term retardants breaks people, displaced thousands, and destroyed Hodges, G. Russian Smokejumpers, National Geographic, Aug 2002: http://environment. up into mist-sized droplets that drift with the more than 1,800 homes. nationalgeographic.com/environment/ wind and evaporate, and only a fraction of the natural-disasters/russian-smokejumpers.html solution lands in the target area in front of the [Aug 2009] advancing fire. The future Wildfire Safety Tips, National Geographic: http://environment.nationalgeographic.com/ “Long-term fire retardants that contain thick- The materials and chemicals used to fight environment/natural-disasters/wildfire-safety- eners hold together and coat vegetation better,” wildfires have come a long way since the early tips.html [Aug 2009] says H. L. “Larry” Vandersall, a technical con- days of battling fires with water. In addition to De Leon, R. How to Become a Wildland Firefighter: http://www.ehow.com/how_4465292_become- sultant for ICL Performance Products. “Color water, firefighters have several reliable chemi- wildland-firefighter.html [Aug 2009] pigments, on the other hand, provide visibility, cal products to choose from, and scientists so that pilots can tie multiple aircraft drops and engineers are developing even more Sherry Karabin is a science writer who lives in New together to form a continuous firebreak.” effective products. York, N.Y. This is her first article in ChemMatters.

12 Chemmatters, FEBRUARY 2010 www.acs.org/chemmatters mericans pump on average 18 million gallons of gasoline per A hour into their cars, but less than half of it comes from oil produced in the United States. To make up for the dif- ference, the United States imports oil from politically unstable regions in the Middle East, Africa, and South America. The United Green Gasoline States could lessen its reliance on imports by drilling more oil, but that may only be a Fuel from Plants temporary solution because many scientists expect that the world’s oil resources will By Michael Schirber eventually dry up. Another solution is to use crops and plants to make gasoline. It might be hard to imagine, but chem- ists can convert corn stalks, sawdust, and grasses into gasoline. They do it by breaking down the plant molecules and reshuf- fling their parts into the same molecules found in gasoline. This new type of gasoline, called green gas- oline, would have many advantages. In addi- it, fill up your car with gasoline that came tion to reducing U.S. dependence on foreign directly from plants. At least that is what some This reac- countries, it would also produce less pollution researchers foresee. The challenge will be to tion is actually than oil-derived fuels, because the plants used figure out how to make large quantities of green an explosion: The to produce green gasoline would absorb some gasoline because, up until now, only small amount of energy in of the pollutants. Also, we would not have to quantities have been made in the laboratory. a pound of gasoline is worry about running out of fuel because green more than 10 times that gasoline is renewable: The plants used to Non-green gasoline found in a pound of trinitro- make it can be grown over and over again. toluene, a common explosive. There are other plant-derived fuels, or bio- Gasoline derived from oil has been the main In a car, this energy heats the fuels, such as ethanol, which is produced by choice for transportation fuel during the past carbon dioxide, water vapor, and the fermentation of plant sugars by yeast, and century. It is stable, noncorrosive, and packs other gases present in the engine, biodiesel, which is made from vegetable oil or a high-energy punch. The energy in gasoline which causes them to expand and to animal fats. But the advantage of green gaso- is stored in molecules called hydrocarbons, push on the engine’s pistons. line is that it can directly replace oil-derived which are long chains or rings made of carbon Most of the time, gasoline inside a gasoline. and hydrogen atoms. When given a spark, the car’s engine is not totally broken down “We wouldn’t have to buy new cars or build to carbon dioxide and new refineries and pipelines just to use green H H H H H H H H water. Some hydro- gasoline,” says chemical engineer Jennifer carbons H C C C C C C C C H Holmgren of UOP, a company in Des Plaines, remain, and some of the fragments end up as carbon Ill., that develops oil-refining technologies. H H H H H H H H In as little as 5 years, you might drive up monoxide (CO), a very toxic gas. The to a filling station and, without even realizing Octane combustion process also can create other pollutants, such as nitrogen oxides (NO carbon and hydrogen atoms combine with and NO2), that lead to smog and acid rain. oxygen in the air, resulting in carbon dioxide, A good deal of this pollution has been water, and a lot of energy. reduced in modern cars. Most of them con- An example of this is the burning of octane

tain a device called a catalytic converter that istoc k (C8H18), one of the hydrocarbons found in filters the pollutants before they are released gasoline: in a car’s exhaust pipe. But this device can-

MI KE CI E SI LS K I not prevent the emission of carbon dioxide, a 2 C8H18 + 25 O2 ➞ 16 CO2 + 18 H2O + energy gas that mixes in with the atmosphere, traps heat from the sun, and contributes to global climate change.

chemmatters, FEBRUARY 2010 13 carbon toluene monoxide

carbon carbon monoxide dioxide

carbon

carbon . h ub e r and dioxide oxygen

toluene ,” by ge or w

indene

(a) (b) (c) (d) toluene zeolite t he pump ant h ony f e rnand ez; adapt d from “g rassolin at 2009. bruc e e. dal e, s cie n ti f ic am r an , july

Turning cellulose into gasoline: Cellulose (a, hydrogen atoms omitted for clarity) is heated to 500 °C, breaking it apart into smaller molecules (b). These molecules bind to a porous substance called zeolite (c). As they bind to the zeolite, these molecules undergo chemical reactions that remove oxygen atoms from them. These reactions result in aromatic molecules (such as toluene and indene), which are components of gasoline, along with other final products, such as carbon dioxide and water (d).

CH OH CH OH CH OH Green gasoline can help lessen the prob- Catalysis and Biocatalysis 2 2 2 lem, because plants absorb carbon dioxide Program at the National Sci- C O C O C O and convert it into organic compounds by ence Foundation, Arlington, H H H H H H C C O C C O C C O using energy from sunlight. The carbon diox- Va. “Gasoline takes less OH H OH H OH H ide is therefore recycled, going from the air to space and is more efficient.” C C H C C H C C H the plants to green gasoline, and then back to The amount of energy per the air, when green gasoline is burned. pound contained in plants H OH H OH H OH Green gasoline is not the only biofuel that can be increased by Cellulose recycles carbon dioxide this way, but it has removing oxygen from the the advantage that it carries the same energy carbohydrate molecules. Octane and other hydrocarbon found in gasoline. But glucose punch as gasoline. hydrocarbons, as mentioned above, burn by contains six additional oxygen atoms, which breaking bonds between carbon and hydrogen reduces its energy content. You would need Packing energy in atoms, which then grab onto oxygen atoms. roughly three pounds of glucose to get the Carbohydrates burn in the same way, but they same amount of energy as one pound of green gasoline already contain some oxygen. In short, if you cyclohexane. Plants store the energy of the sun in organic remove as many oxygen atoms as you can molecules called carbohydrates, which include from a molecule, it will pack more energy. sugars and cellulose—the main constituent of As an example, the sugar glucose (C6H12O6) a plant cell wall. This energy can be extracted is similar in shape to cyclohexane (C6H12), a directly by burning the plants. For example, in the 19th century, some steam ships were H H H H powered by burning wood. But burning wood or other plant materials to run your car is not CH OH CC 2 H H practical. They do not flow into the engine like O H OH CC liquid fuels do, and you would need to carry H H H three times as much weight in wood to go the OH H C C OH H same distance as with gasoline. H H “We use gasoline because it packs a lot of H OH H H energy,” says John Regalbuto, director of the Glucose Cyclohexane uop llc

14 Chemmatters, FEBRUARY 2010 www.acs.org/chemmatters Scientists at the University of Wisconsin, at the University of Massachusetts, Amherst. Other researchers, such as Lanny Madison, have successfully stripped oxygen He and his colleagues have developed a Schmidt, professor of chemical engineer- atoms from glucose and other sugars to cre- technique that can turn almost any plant sub- ing and materials science, and colleagues ate hydrocarbons similar to cyclohexane. The stance into gasoline. at the University of Minnesota, Twin Cities, resulting liquid is essentially gasoline, but it The plant materials are first placed in a are heating plant ingredients to higher tem- is “green” because it is extracted from plants, reactor at 500 °C. This breaks down the cel- peratures (700 °C–1,000 °C) to produce a not oil. lulose and other tough plant parts into smaller gas mixture of carbon monoxide (CO) and Virent Energy Systems, a renewable energy molecules, called anhydro sugars. These hydrogen (H2). These molecules of gas are company based in Madison, is working on this molecules then go through a porous structure then reassembled into hydrocarbons, such sugar-to-hydrocarbon process and is planning called a zeolite, which is made of aluminum as octane, with water as a byproduct: to produce 100 million barrels of green gaso- and silica. The pores are designed to be just line in 5–7 years. big enough for the anhydro sugar molecules 8 CO + 17 H2 ➞ C8H18 + 8 H2O to enter. Energy from plant “If the size of the pores is too small, the molecules can’t get in,” Huber says. “If they The future leftovers are too big, too many molecules crowd in, and All of these processes remain under devel- Carbohydrates, such as glucose, are unwanted reactions opment. “We are still in the early days of typically derived from sugarcane or corn. But occur.” This can green gasoline,” says Robert Anex, associate using these food crops for the production of result in a carbon- professor of agricultural and biosystems engi- green gasoline runs the risk of driving up food rich material that neering at Iowa State University in Ames. clogs up the zeolite. So far, there are logistics problems, such The pores in as how to collect cornstalks from widely Huber’s zeolites are separated farms and bring them to one central about six atoms facility. And although the chemistry works well wide, which is room in a laboratory, it is not yet clear whether the enough for an anhy- same processes will work on a large scale.

dro sugar molecule b e n barn h art But green gasoline holds a lot of promise, George Huber poses with to enter and attach a vial of green gasoline and scientists, engineers, and policymakers to the surface, compounds. are now starting to realize it. Says Holmgren, where it loses “Energy is the most important challenge fac- its oxygen and re-forms into a ring-shaped ing us today, and chemistry will play a key hydrocarbon similar to cyclohexane but with role in making sure we have an alternative vir e nt n r g y syst ms Virent’s Liquid Fuel Laboratories less hydrogen atoms. The full process—from source of energy into the next 100 years.” breakdown in the reactor to hydrocarbon for- prices. It would be better to make green gaso- mation—takes just a few seconds. line with plant materials that are not used. Holmgren and her UOP colleagues are Current research is looking at agricultural working on a similar project. They start by and forestry “leftovers,” such as cornstalks placing plant materials into a vessel that and sawdust, and nonfood crops, such as whips up a tornado of hot sand. This swirling switchgrass and other prairie grasses that can sandstorm rapidly heats the plant matter to Selected references be grown without much 500 °C, thereby cooking it into an oily liquid. Huber, G.; Dale, B. Grassoline at the Pump. irrigation or fertilizer. This liquid is then processed into gasoline and Scientific American, July 2009. Kintisch, E. The Greening of Synfuels. Science, More than 1 billion other fuels. April 18, 2008. tons of plant leftovers are Savage, N. Making Gasoline from Bacteria. available each year in the Technology Review, Aug 1, 2007: United States, according http://www.technologyreview.com/read_article. aspx?ch=specialsections&sc=biofuels&id=191 to a study by the U.S. 28&a [Sept 2009] Department of Agriculture Development of Cellulosic Biofuels: Video lecture

S t e p he n A usmus and the U.S. Department by Chris Somerville, director of the Energy Switchgrass of Energy. This could Biosciences Institute at the University of California, Berkeley: http://tinyurl.com/ produce 100 billion gal- grassoline [Sept 2009] lons per year of green gasoline—about half the Green Gasoline: A Renewable Petroleum Alternative current U.S. annual consumption of gasoline from Plants: http://www.nsf.gov/news/newsme- dia/greengasoline/index.jsp#added [Sept 2009] and diesel. One of the scientists working on the conver- Michael Schirber is a science writer who sion of plant leftovers into gasoline is George lives in Lyon, France. This is his first article in

Huber, a professor of chemical engineering istoc k ChemMatters.

chemmatters, FEBRUARY 2010 15

istock

k istoc

By Jane Andrew

ne of the hottest recent trends “‘Mineral makeup’ is a marketing term prevent the growth of bacteria but can irritate in cosmetics is “mineral often applied to traditional cosmetic formulas sensitive skin. But nearly all of the mineral makeup,” products made of without any real, significant changes to the raw material used in makeup is synthesized or mineral-based powders without ingredients themselves,” says Susan Vogel, chemically processed, she says. Also, some theO additives and preservatives found in tra- a senior product manager for Saint-Gobain common ingredients of mineral makeup— ditional makeup. Originally sold in dermatolo- Avanced Ceramics, Amherst, N.Y., a company such as bismuth oxychloride and boron gists’ offices to laser-treatment patients, such that makes ceramic materials, including boron nitride—are entirely synthetic, she adds. products can now be found in the corner nitride, an ingredient used in mineral makeup. drugstore. The market trend began quietly What is makeup in 1998 when Leslie Blodgett, chief execu- tive officer of the cosmetics company Bare made of? Escentuals, first presented the bareMinerals Mineral makeup combines several differ- foundation on the TV home shopping network ent properties at once. It needs to slide easily QVC. The product quickly sold out, and Bare onto the skin, adhere well to the skin, and Escentuals became a top seller on QVC. hide imperfections in In 2001, another company, Pür Minerals, the skin—a property

started selling mineral makeup. Today, most MI KE CI E SI LS K I called coverage. Then, leading names in the cosmetics industry the combination of have products labeled as mineral makeup. all of the ingredients In this article, we look at the claims about needs to produce the this makeup, what it contains, and how the Paula Begoun, a cosmetics industry expert, desired color. istoc k makeup’s ingredients are chosen. agrees. “Mineral makeup is nothing revolu- Two main ingredi- Most mineral makeup tionary or failsafe,” she says. “It is simply ents of most mineral is made of (white, a type of powder foundation created from a makeup are talc above) talc and mica Is it what they say powders. blend of ‘powdery’ substances.” it is? Begoun acknowledges that mineral Mineral makeup is marketed as being “natu- makeup contains a large number of com- ral” because it is made of minerals found in pounds that occur in nature and that most nature. Ads imply that this type of makeup is mineral makeup products are free of fra- new, different, and safer. But that may not be grances and preserva- completely true. tives—chemicals that

16 Chemmatters, FEBRUARY 2010 www.acs.org/chemmatters and mica powders. These powders help the Covalent bonds Better mineral makeup slide on the skin and reflect light, Nitrogen (N) atoms and mica can provide a range of colors. makeup? Titanium dioxide and zinc oxide powders are Although the current craze for mineral van der Waals bonds also used. They contribute to adhesion and makeup does not seem to depend upon coverage and help protect the skin from the anything new, people will always be looking Boron (B) atoms sun’s ultraviolet radiation. for ingredients with better slip, adhesion, But the workhorse ingredients in mineral coverage, or color—at a better price. The case makeup are iron oxide pigments, which of boron nitride is one example. It was devel- come in one of four color ranges: red, yellow, ant h ony f e rnand ez oped in the 20th century, but new processing black, and green. The red pigments range techniques were needed to bring its unique properties into a new market. In what unex- from a light salmon color to a deeper blue- Figure 1. Boron nitride is structured in layers of red, for instance. hexagonal rings; each ring contains three boron pected corner will you find the next mineral The pigments are blended to make differ- atoms (black) and three nitrogen atoms (green). miracle? ent shades for different skin tones. Red iron oxide pigments have the same structure and composition as the mineral hematite (Fe2O3), black pigments are like magnetite (Fe3O4), and yellow pigments are like goethite (FeOOH).

Boron nitride: A good alternative? Many brands of mineral makeup contain bismuth oxychloride (BiOCl), a chemical that improves the feel of mineral makeup powder and provides a shimmery effect. Although this chemical is approved for cosmetic use, it can irritate the skin by making it red or ant h ony f e rnand ez Figure 2. Within a layer of boron nitride, boron and nitrogen atoms form covalent bonds by sharing itchy. Also, the skin may burn, develop small electrons (each line on the diagram represents a bond using two electrons). An atom of boron contributes bumps or pustules, and look swollen. three valence electrons and an atom of nitrogen contributes five valence electrons, so once the in-plane The reason is that while bismuth oxychlo- bonds have formed their hexagonal grid, there is one remaining pair of electrons per BN unit. Because nitrogen is more electronegative than boron, these electrons are disproportionately located on the N ride is a common ingredient in cosmetics, atoms (left-hand figure), but they are to some extent shared between the atoms (right-hand figure). The it is used in much higher concentrations true structure is an average of these individual pictures. in mineral makeup, says Steve Kramer, president of Coastalscents.com, a cosmet- ics company that offers high-quality mineral makeup at an affordable price. “The atoms bond mostly with one another Selected references To avoid this problem, Coastalscents.com inside the layers but not between the layers, “Mineral Makeup: Centuries-Old Product in New Wrapper.” Morning Edition, National Public and other companies make mineral makeup so it is easy for these layers to slide around,” Radio, June 23, 2008. with boron nitride powder, which is not only Vogel says. “The structure of boron nitride is Begoun, P. Mineral Makeup: Powder Perfect or shimmery but also chemically unreactive— similar to that of graphite, the type of carbon Poor Performer? http://www.cosmeticscop. and thus less likely to be irritating. Boron present in pencils. Just as graphite slips eas- com/skin-care-facts-mineral-makeup.aspx [Aug 2009] nitride’s properties result from its structure, ily from a pencil onto a piece of paper, boron Valhouli, C. Mineral Makeup: Excavated From a which is made of layers, each layer contain- nitride powder slides smoothly onto the skin.” Mine. The New York Times, Aug 24, 2006, ing hexagonal rings of boron and nitrogen The layers also make boron nitride unreac- p G. 3. atoms (Fig. 1). tive. To understand why, we need to look at Gabriel, J. Green Beauty Guide: Your Essential Besides the glimmer, the reflection and the boron-nitrogen bond. To form a stable Resource to Organic and Natural Skin Care, Hair Care, Makeup, and Fragrances. Deerfield Beach, scattering of light also help hide lines and covalent bond, the boron and nitrogen atoms FL: Health Communications, Inc., 2008. imperfections in the skin. Boron share eight valence electrons. Boron can nitride’s layered structure has contribute three electrons from its outermost Jane Andrew is a science writer who lives in Oak other good properties. Within energy level; nitrogen can contribute five. The Park, Ill. This is her first article in ChemMatters. each layer, boron and nitrogen shared electrons distribute themselves into atoms form strong covalent three bonds that point to the corners of an bonds, whereas the layers are equilateral triangle. When the points of these held together by weak van der triangles combine, the result is hexagonal

Waals forces. rings (Fig. 2). istock

chemmatters, FEBRUARY 2010 17 MI KE CI E SI LS K I PROFILES IN CHEMISTRY

Interview with Chris Pollock Chemistry Graduate Student By Dan Risch C l e mson U niv rsity Chris Pollock is shown analyzing a film of a chemical called polydiacetylene that he and others made to look like tiger paws (Clemson University’s mascot).

t probably was inevitable. Chris Pol- know why we put salt on the roads in winter. lock, a first-year student at Clemson What I learned from my chemistry class pro- University, Clemson, S.C., had com- vided the answer: While water freezes at 0° C, pleted a chemistry exam about Gibbs salty water freezes at lower temperatures—as freeI energy (a measure of the tendency of a low as –30 °C, depending on how much salt chemical change to occur spontaneously). is added to the water. So, salty water can Walking back to his dorm, a stray cat sidled stay liquid even if the air temperature is 0 °C up to Chris, who couldn’t turn it away. After or lower (as long as it is above the freezing all, when he arrived on campus in 2005, Chris temperature of the salty water). Scientists call signed on as a volunteer at the Clemson ani- this phenomenon freezing point depression.

mal shelter. So Chris gave the cat a home and The freezing temperature is “depressed,” or S out he ast e rn Exp ditions , I nc . a name—Gibbs. Chris seems to have a way of reduced to a value that is lower than 0 °C. Chris Pollock (back, second from left) enjoys whitewater rafting with other students on the making connections, chemically. Another time, we were discussing ionic Chattooga River during the 2007 EUREKA! A member of Clemson’s prestigious Cal- compounds, which are made of positive and (Experiences in Undergraduate Research, houn Honors College, Chris graduated with a negative ions. Then, one day, I was reading Exploration, and Knowledge Advancement) summer program at Clemson University. major in chemistry and a grade point average the ingredients on a cereal box and it hits (GPA) of 4.0. Just prior to graduating in May me, “Hey! I know what magnesium sulfate help in forensics investigations and in finding 2009, Chris was named Outstanding Senior in is! It is an ionic compound.” That struck me contaminants in food. All of this opened my the Sciences. as so cool. I began to realize that I could eyes about what people can do with chemis- I recently caught up with him as he was explain things chemically from what I had try and made me want to major in chemistry pursuing his graduate-level chemistry studies learned in class. in college. at Cornell University, Ithaca, N.Y. After the 10th grade, I took advanced placement (AP) How did you get interested in chemistry? chemistry. I had a fantastic I took my first chemistry class when I was teacher who got me excited in 10th grade. I couldn’t stand it. All we were about looking at the chemistry doing was math, converting miles to kilo- in the world around me. For meters and things like that. But, as the year example, in my senior year, we went on, chemistry became more interesting used a device called a spec- because we studied things more related to our trophotometer to measure everyday world. the amount of light absorbed For example, we studied what happens by different chemicals in a when you dissolve chemicals in water and sample. With this instrument, e nt De partm C l e mson U niv rsity ’ s Che mistry you can scan a sample to Chris Pollock (second from right) and other members of Clemson how this affects the way water freezes and University’s chapter of the Student Affiliates of the American boils. Being from Pennsylvania, where we identify what chemicals are in Chemical Society (SAACS) won the American Chemical Society have plenty of snow and ice, I was curious to it. These measurements can Award for their contributions to the SAACS chapter.

18 Chemmatters, FEBRUARY 2010 www.acs.org/chemmatters Did you do any cool research in States, gives students information on chemistry while in college? what is happening in chemical labs and Yes, I was part of a team of sci- the chemical industry, and helps them entists who are looking for ways to find a job later. In my opinion, these are deliver drugs in the body. The head invaluable services when you want to of the team is Ivan Dmochowski, a feel part of a community, stay current professor of chemistry at the Univer- on what’s happening in the field, and sity of Pennsylvania in Philadelphia. receive tips on how to apply for jobs or I am from Allentown, Pa., which is graduate school. about 60 miles north of Philadelphia, Last year, I was the president of so I was able to work with the Dmo- Clemson’s Student Affiliates program, C l e mson U niv rsity chowski group during the summer Chris Pollock (second from left) and other members of Clemson and I had a blast! Some of the things University’s chapter of the Student members of the American I did were to work with other students of 2008. I was interested in their work Chemical Society, along with Katie Hunt, past president of the blending new nonorganic materials, American Chemical Society. on presenting posters at the 2008 such as metals, with organic materi- annual meeting of the American Chem- als, such as proteins. The candle got lighter. We thought, well, when ical Society in New Orleans and to help high Dmochowski’s team is working on ways you burn something, it ought to get lighter. school students from the area be involved in to make anticancer drugs work better. Most Our hypothesis was that because the wick and chemistry meetings and activities at Clemson of these drugs are very effective, but they are the wax had probably combined with oxygen University. very toxic to nearby healthy cells, too. Dam- to produce carbon dioxide and water, the age to these healthy cells can result in hair candle lost atoms and became lighter. It was What would you like to do after you falling out, nausea, and other health problems. kind of fun. finish your studies? But if you can get the drug right into the A lot of my classmates decided they hated I really like biochemistry and metals. So I tumor and not into nearby cells, you can avoid chemistry before they even started. But I am trying to find ways to combine biochem- these undesirable side effects. think if you go into chemistry with an open istry and inorganic chemistry to look at how Dmochowski and colleagues are using mind, you may find you like it. That’s what metals affect biological systems. It is called particles made of hundreds of gold atoms happened to me. bioinorganic chemistry. clumped together, called gold nanoparticles. I haven’t decided whether I want to go into When these nanoparticles absorb light, they academia or go into industry and work for I think get hot. So, what I did was to glue them inside a company. I think I will end up in academia a hollow particle called a liposome, which if you go into because it offers more freedom to do your looks like a tiny bubble. I put these liposomes chemistry with work. As an academic scientist, you can usu- in a lab dish and hit them with ultraviolet an open mind, ally decide in which direction to take your light. The gold heated up and the liposomes you may find research. You don’t necessarily have that free- popped. you like it. dom in industry. Someday, we hope to put a drug into lipo- I have been surprised by all the different C l e mson U niv rsity somes designed to detect cancer cells and go places chemists can work. Around Clemson, inside them. Scientists would inject these lipo- The American Chemical Society’s there is Kodak and Michelin. In nearby Atlanta, somes into someone who has cancer and then “Student Affiliates” program acts as there are the federal Centers for Disease pop them by shining infrared light (the kind of a chemistry club for undergraduate Control and Prevention and companies like light that can pass through the body) over the students. Why was it important for you Air Products and 3M. And even without leav- spot where the drug is needed. Cool, huh? to join this club at Clemson and what ing campus, chemists work through grants have you learned from it? funded by the National Institutes of Health, Do you remember your first classes Chemistry doesn’t happen in a vacuum. Bethesda, Md. in chemistry? Everything you do can positively affect oth- I remember that the room was a lab and a ers in some way. The best way to do that is Any advice you would like to share with classroom combined. In the first half was the through networking. And that works from ChemMatters’ readers? classroom, and in the back half was the lab elementary school to college to professional I would say do whatever you are excited with three or four benches. I remember looking societies, where at meetings you show people about. If you are not excited, you won’t enjoy back there and seeing all this glassware, Bun- the research you have done and look at what it. If you study something you enjoy, you want sen burners, and compound jars sitting out. It they are doing. Maybe what you have done to know more about it. That propels you for- looked like an alchemist’s lab. I thought, “How can help them, and their work can help your ward and it’s much more enjoyable and much do you use a beaker? How do you use a flask?” project move further along. It’s all about shar- more productive. In our first experiment, we placed a candle ing what you learn. on a balance and made it perfectly level. Then The Student Affiliates program helps under- we lit the candle and let it sit. After 5 or 10 graduate students network with other chemis- Dan Risch is a freelance writer in Louisville, Ky. minutes, the balance wasn’t level anymore. try students and chemists around the United This is his first article in ChemMatters.

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