Chemistry Is All Around Us

Chemistry is all around us. Everyone can and should understand basic chemistry. The Story Apart from those wanting to become chemists, students Central wanting to become doctors, nurses, physicists, Science

Cover nutritionists, geologists, and pharmacists all need to study chemistry. It is important to remember that the Chemistry importance of chemistry would not be diminished BIMAN BASU over time; rather it will continue to remain a That is not all. There would be no drugs a science. It was primarily directed at efforts promising career prospect. – painkillers, antacids, or antibiotics – no to turn all kinds of substances into the polyester fibre or nylon stockings, no precious metal gold by early chemists, who stainless steel, no sugar-free soft drinks, were known as alchemists. We have heard IGHT from the moment we get up in even no Diwali illumination and fireworks about the “philosopher’s stone” using which the morning till we go to bed at without chemistry. Without chemistry, we the alchemists sought to turn any metal night, we come intimately close to R would not have such items as computers, into gold. Of course it was a silly thought, chemistry and things related to it. The CDs, DVDs, iPods, fuel for vehicles, oil to because no one can really turn one toothpaste we use to clean our teeth, the cook, refrigeration units, radios, televisions, element into another by mere touch! Still, toilet soap, shampoo, and plastic buckets batteries, and so much more. So, then, the alchemists made important we use to take bath, the plastic comb we what is chemistry? contributions to chemistry; they developed use to comb our hair, the melamine cups many of the techniques used by modern and plates we use at breakfast, the cooking gas our mother uses in the kitchen, Chemistry Around Us chemists like distillation, filtration, etc., and the iodised salt she uses to cook food, the In brief, we can say, chemistry is all about were also the first to use symbols for some ink in the pen we write with, the inks this the nature of all matter around us – air, common elements like gold and mercury. magazine is printed with, the beautiful dyes water, metals, plastics, drugs, everything – The real importance of chemistry that brighten up our dresses, the about how they behave, how they react, stems from the fact that it serves as a polyurethane foam mattress that makes and how they change. It is about changing common interface between practically all our sleep at night comfortable, and a host one kind of material into another. of the other sciences – medicine, biology, of other items of daily use are all products In fact, the practice of chemistry engineering, geology, and manufacturing of chemistry. started thousands of years ago, but not as – as well as between many other areas of

Chemistry serves as a common interface between practically all of the other sciences Even fireworks are possible only because of chemistry

SCIENCE REPORTER, APRIL 2011 88 CoverCoverCover Story

There would be no drugs, stainless steel, sugar-free soft drinks, CDs, DVDs and iPods, televisions and a host of other things without chemistry

Apart from those wanting to first published in 1977, with a 12th edition published in 2011.) become chemists, students This is not an overstatement, because wanting to become doctors, a student with a solid background in nurses, physicists, nutritionists, chemistry would find it far easier to migrate into other fields as his/her interest develops. geologists, and pharmacists all But, unfortunately, many science students chemical elements – the simplest need to study chemistry. find chemistry boring, and some find it a substances into which ordinary matter may human endeavour such as art and culture very hard subject to understand. But that be divided – and the way they react with where paints, colours, dyes and fabrics – need not be so. each other. As early as 1660, Irish-born all products of chemistry – play a key role. Chemistry is primarily concerned with chemist Robert Boyle recognised that the For this reason, chemistry is often called Greek definition of element (earth, fire, air, the “central science”. (The phrase was and water) was not correct. Boyle popularised in a textbook by Theodore L. proposed a new definition of an element Brown and H. Eugene LeMay titled as a fundamental substance, and we now Chemistry: The Central Science, which was define elements as fundamental John Dalton’s atomic theory could explain the facts of substances that cannot be broken down chemical combination as they were then known (below), further by chemical means. But Boyle did Various atoms and molecules as depicted in John Dalton’s not elaborate on the nature of the A New System of Chemical Philosophy (1808) (right) elements or compounds. The 118 chemical elements known today constitute the “alphabet” of matter because everything else is made of some combination of these. (Of course, many of the transuranium elements do not occur in nature; they are artificially produced.) The elements can combine by reacting together to form a multitude of compounds that make up everything in this universe, including us. Everything around us is formed by a combination of two or more of these elements. So, in order to understand chemistry one has to know about the chemical elements, about their properties, about how they react, and about why they react the way they do. But doing that is not as difficult a task as it may sound. It is possible 9 SCIENCE REPORTER, APRIL 2011 CoverCoverCover Story Friedrich Wohler overturned the vitalism theory by converting the inorganic salt ammonium cyanate into urea, which is an organic compound (right);

Friedrich August Kekulé brought in a revolution in structural chemistry by suggesting a ring structure for benzene (extreme right)

Dmitri Mendeleev was able to bring of chemical combination as they were that a chemical compound always a system of classifying the elements then known. The idea of atoms had been contains same elements combined that made their study easier proposed much earlier. The ancient Greek together in the same proportion by mass. philosophers had talked about atoms, but These were great achievements in to learn about the elements even without Dalton’s theory was different in that it was understanding how the chemical elements memorising complex equations and supported by careful chemical combine. All the three scientists formulated formulae. Of course, getting familiar with measurements. It was not just a their laws after careful and extensive the chemical symbols can be of great help philosophical statement. experimentation – an essential prerequisite in understanding the subject better, as Dalton’s atomic theory specifically of chemistry. would a little understanding of how stated that elements consisted of tiny chemical formulae and equations are particles called atoms. It further said that Periodic Properties of written. the reason an element is pure is because Elements all atoms of an element were identical Laws of Chemistry Before the Russian chemist Dmitri and that in particular they had the same Mendeleev came up with the periodic The real joy of learning chemistry comes mass. It also said that the reason elements table of elements in 1869, understanding from understanding its basic laws. If we look differed from one another was that atoms and remembering the properties of all the at the history of science we will come of each element were different from one 63 chemical elements known at that time across numerous instances where a another; in particular, they had different was a stupendous task. Mendeleev was sudden spark lit up a dark tunnel leading masses. Dalton’s theory also said that able to bring a system of classifying the to the solution of a long-sought problem. compounds consisted of atoms of elements which made the job easier. Chemistry also evolved in small steps, different elements combined together. He Although Mendeleev arranged the each marked by a unique discovery. used his own symbols to visually represent elements in order of increasing atomic One of the first big breakthroughs in the atomic structure of compounds. mass, which was incorrect, his periodic our understanding of chemistry came in There are millions of chemical table brought some order in an apparently 1803 when English physicist, meteorologist compounds formed by elements in random collection of elements. and chemist John Dalton proposed a different combinations; yet all of them are Mendeleev also did a few things that rational atomic theory to explain the facts guided by three simple laws of chemical made his table useful. He realised that the combination, which were propounded physical and chemical properties of Carrying between 1785 and 1806. elements were related to their atomic mass matters further, The law of conservation of mass was in a ‘periodic’ way, and arranged them so the French discovered by French chemist Antoine that the elements with similar properties chemist Pierre Laurent Lavoisier about 1785. It states that fell into vertical columns, or ‘groups’, in his Eugene during any physical or chemical change, table. Marcelin the total mass of the products remains Berthelot went equal to the total mass of the reactants. A major about John Dalton formulated the law of multiple synthesising proportions in 1803. According to this law, turning point organic if two elements form multiple compounds, in chemistry compounds the ratios of the masses of the second was the systematically, element combining with a fixed mass of refutation of turning them the first element will be in ratios of small the long held out in scores whole numbers. Three years later, the during the French chemist Joseph Proust stated the ‘vital force’ Robert Bunsen Gustav Kirchhoff 1850s. law of constant proportion, which states theory SCIENCE REPORTER, APRIL 2011 10 Cover Story

The work of William Lawrence Bragg created a new science of X-ray crystallography. Here he is seen delivering a lecture.

In Mendeleev’s table there were gaps Henry Moseley, who worked with New in the horizontal rows or ‘periods’ where no Zealand-born British chemist Ernest known element could be placed. But Rutherford, showed that it is atomic instead of seeing this as a deficiency of his number and not atomic mass, which is table, Mendeleev thought it simply meant most fundamental to the chemical that the elements which belonged in the properties of any element. Moseley gaps had not yet been discovered. He correctly predicted the existence of new could also work out the atomic masses of elements based on atomic numbers. We the missing elements, and so predict their know now that an element’s chemistry is properties. When the unknown elements indeed determined by its atomic number were discovered, Mendeleev turned out and the way its electrons are arranged – to be right. For example, he predicted the its electronic configuration. The electronic properties of an undiscovered element configuration could explain why some that should fit below aluminium in his table, elements are more reactive than others, William Lawrence Bragg, who which he called ekaaluminium. When this why some elements are totally inert, and was 22 years old, realised that also why some elements are unstable. element, called gallium, was discovered X-rays could be used to detect in 1875 its properties were found to be Slowly scientists were beginning to close to Mendeleev’s predictions. Three understand how chemistry works. the arrangement of individual other predicted elements – atoms inside solid crystals. ekamanganese (technetium), ekasilicon Fall of Vitalism (germanium), and ekaboron (scandium) A major turning point in chemistry was the In 1807, Swedish chemist Jons Jacob – were later discovered, lending further refutation of the long held ‘vital force’ Berzelius suggested that substances like credit to Mendeleev’s table. Suddenly the theory to explain existence of organic olive oil or sugar, the characteristic properties of the elements not only compounds. Till the early 19th century, products of living organisms, be called became rationalised but also predictable. scientists commonly believed that there organic. Substances like water or salt, Mendeleev could make little further were two classes of chemical substances characteristic of the non-living progress because the Rutherford-Bohr – those produced by non-living environment, were inorganic. A significant model of the atom had not yet been environment and those produced by living observation that seemed to corroborate formulated. Then in 1913, English physicist organisms. Berzelius’s point of view was that organic 11 SCIENCE REPORTER, APRIL 2011 Cover Story

The resonant structures of benzene, as proposed by Kekulé

Chemistry is all about the nature of all matter around us – air, water, metals, plastics, drugs,

Robert Burns Woodward, who showed that natural everything – about how they behave, how they products could be synthesised by careful applications of react, and how they change. It is about changing the principles of physical organic chemistry, and by meticulous planning one kind of material into another.

substances could be easily converted, by undermined the vital force theory that held Kekule’s Snake and Benzene heating or other harsh treatment, into sway for centuries, by showing that organic Structure inorganic substances. But no one knew of compounds could be synthesised from The empirical formula for benzene was the reverse change – of an inorganic inorganic materials. long known, but its highly polyunsaturated substance turning into an organic one. Other similar successes followed structure, with just one hydrogen atom for Wohler’s work. In 1847 German chemist Chemists who believed in vitalism each carbon atom, presented a serious Hermann Kolbe synthesised acetic acid predicted that organic materials could not challenge for chemists. They could not from inorganic compounds for the first time. be synthesised from inorganic think of any conventional structure that This reaction sequence consisted of components. It was commonly believed could account for all the carbon bonds in chlorination of carbon disulfide to carbon that organic substances required the vital benzene. Then, in 1865, German chemist tetrachloride, followed by pyrolysis to force, found only in living beings. Chemists Friedrich August Kekulé brought in a tetrachloroethylene and aqueous working with ordinary substances and chlorination to trichloroacetic acid, which revolution in structural chemistry by techniques and without being able to was subsequently electrolytically reduced suggesting that the benzene structure manipulate a vital force in their test tubes to acetic acid. contained a six-membered ‘ring’ of could not bring about this conversion. Carrying matters further, the French carbon atoms with alternating single and But this belief was overturned by a chemist Pierre Eugene Marcelin Berthelot double bonds. (Kekule is said to have single experiment in1828, when German went about synthesising organic stumbled upon the ring shape of the chemist Friedrich Wohler, who had been a compounds systematically, turning them benzene molecule after having a reverie pupil of Berzelius, accidentally converted out in scores during the 1850s. These or day-dream of a snake seizing its own the inorganic salt ammonium cyanate into included such well-known compounds as tail!) a purely organic compound urea by methyl alcohol, ethyl alcohol, methane, Kekulé was the principal formulator simple heating. Actually Wohler was trying benzene, and acetylene. With Berthelot, of the theory of chemical structure, which to synthesise ammonium cyanate by crossing the line from inorganic to organic arose out the idea of atomic valence, heating various combinations of cyanates ceased to be a thrilling intrusion upon the especially the tetravalence of carbon of silver, lead and mercury, and “forbidden”, and became purely routine. (which Kekulé had announced late in 1857) ammonium salts. In the course of the heating, Wohler discovered formation of It is important to crystals resembling those of urea, a waste product eliminated in considerable remember that the quantity in the urine of many animals, importance of including humans. Closer study showed the crystals were undoubtedly urea, which chemistry would not was, of course, clearly an organic be diminished over The compound. In the reaction ammonium spectroscope cyanate appeared only as an time; rather it will built by intermediate before being transformed continue to remain a Bunsen and into urea. Remarkable as the finding was, Kirchhoff to this synthesis was a landmark in the history promising career study elements of science which disproved and prospect. SCIENCE REPORTER, APRIL 2011 12 Cover Story

Mendeleev’s 1872 periodic table. The spaces marked with blank lines represent elements that Mendeleev deduced existed but were unknown at the time, so he left places for them in the table. The symbols at the top of the columns are molecular formulas written in the style of the 19th century. and the ability of carbon atoms to link to But following the invention of the more exotic types of bonding in inorganic each other (announced in a paper spectroscope, the search was on for trace chemistry, such as metal-metal double published in May 1858). For organic elements detectable only with the help of bonds, metal-metal quadruple bonds, and chemists, the theory of structure provided specialised instruments like the three-centre, two-electron bonds. a new clarity of understanding, and spectroscope. The spectroscope also Since the 1920s, X-ray diffraction has proved to be of immense help for both made it possible for astronomers to learn been the principal method for determining analytical and synthetic work. As a result about the composition of the Sun and the the arrangement of atoms in not only large of these developments, the field of stars. In fact, the element helium was first organic molecules but also minerals and organic chemistry developed rapidly from detected on the Sun using spectroscopy metals. In 1953, it was through the study of this point. long before it was discovered on Earth. X-ray diffraction patterns that American One of the most powerful tools for molecular biologist James Watson and Tools of Chemistry structure determination of complex English molecular biologist Francis Crick could unravel the molecular structure of Development of analytical tools played a molecules is X-ray diffraction, the DNA – the carrier of genetic information in major role in the advancement of brainchild of a young English physicist. In the autumn of 1912, William Lawrence all living beings – that ushered in the chemistry. In 1859 German chemists Robert Bragg, who was 22 years old, realised that modern age of biotechnology and Bunsen and Gustav Kirchhoff invented the X-rays could be used to detect the recombinant DNA technology. For this work spectroscope with which they discovered arrangement of individual atoms inside Watson and Crick were jointly awarded the two alkali metals, caesium and rubidium. solid crystals. With his father’s help he Nobel Prize for Physiology or Medicine for These discoveries ushered in a new era in created a new science of X-ray 1962. the means used to find new elements. The crystallography. For his insight, Lawrence first 50 elements discovered – beyond Bragg became the youngest ever Nobel Chemical Synthesis those known since ancient times – were Laureate in 1915. One of the things that make chemistry either the products of chemical reactions X-ray crystallography opened up a unique among the sciences is chemical or were released by electrolysis. whole new world of atoms and molecules. synthesis, which is actually the purposeful The technique led to a better execution of chemical reactions to get a understanding of chemical bonds and product, or several products. Using various non-covalent interactions. The initial studies techniques of chemical synthesis, chemists revealed the typical radii of atoms, and create things, new pharmaceuticals, food confirmed many theoretical models of additives, materials, agricultural chemicals, chemical bonding, such as the tetrahedral coatings, adhesives, and all sorts of useful bonding of carbon in the diamond new molecules. They prepare them from structure. X-ray crystallographic studies simpler, more readily available starting have also led to the discovery of even materials. 13 SCIENCE REPORTER, APRIL 2011 Cover Story

The chemical synthesis of complex or even make a career out of it. It is organic molecules is integral to many Chemists who believed in vitalism important to understand chemistry if one advances that enhance the quality of life, predicted that organic materials is studying any of the sciences because such as novel pharmaceuticals, could not be synthesised from all of the sciences involve matter and the agrochemicals without harmful inorganic components. interactions between types of matter. environmental impact, and advanced Apart from those wanting to become materials for high-performance chemists, students wanting to become Despite the past achievements, there technology. In the total synthesis of a doctors, nurses, physicists, nutritionists, still remains a lot to explore and discover complex product it may take multiple geologists, and pharmacists all need to in chemistry. Novel molecules like steps to synthesise the product of interest, study chemistry. fullerenes, graphene, and many others and inordinate amounts of time. It is important to remember that the offer ample scope of research and Skill in organic synthesis is prized importance of chemistry would not be development, which any talented student among chemists and the synthesis of diminished over time; rather it will continue can take up as a challenge. exceptionally valuable or difficult to remain a promising career prospect. compounds has won chemists such as American organic chemist Robert Burns Why Learning Chemistry is Mr Biman Basu was editor of Science Reporter Woodward the Nobel Prize for Chemistry. Important for more than 30 years. Winner of the 1994 NCSTC Woodward is credited with synthesising Apart from its multifarious involvement in National Award for best science and technology many complex natural products including our daily life, chemistry is so deeply coverage in the mass media, Mr Basu has been quinine, cholesterol, cortisone, strychnine, ingrained in so many areas of business, involved in science communication through his popular science writings, radio talks and popular lysergic acid, reserpine, chlorophyll, government, industry, and environmental lectures for more than four decades. A prolific writer cephalosporin, and colchicine. With management that some background in on a wide range of S&T topics, Mr Basu has to his these, Woodward opened up a new era the subject can be useful in fields as varied credit more than 1,000 popular science articles and of synthesis, sometimes called the as product development, marketing, over 500 radio talks and features. He has also ‘Woodwardian era’ in which he showed management, computer science, written about 30 popular science books, many of that natural products could be synthesised technical writing, and even law. which have been reprinted several times. by careful applications of the principles Everyone can and should understand Address: C-203, Hindon Apartments, of physical organic chemistry, and by basic chemistry, and it would be 25 Vasundhara Enclave, Delhi-110096 meticulous planning. worthwhile to take a course in chemistry Email: [email protected]

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