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iranchembook.ir/edu iranchembook.ir/edu The Facts On File DICTIONARY of ORGANIC CHEMISTRY iranchembook.ir/edu iranchembook.ir/edu The Facts On File DICTIONARY of ORGANIC CHEMISTRY Edited by John Daintith ® iranchembook.ir/edu The Facts On File Dictionary of Organic Chemistry Copyright © 2004 by Market House Books Ltd All rights reserved. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval systems, without permission in writing from the publisher. For information contact: Facts On File, Inc. 132 West 31st Street New York NY 10001 Library of Congress Cataloging-in-Publication Data The Facts on File dictionary of organic chemistry / edited by John Daintith. p. cm. Includes bibliographical references. ISBN 0-8160-4928-9 (alk. paper). 1. Chemistry—Dictionaries. I. Title: Dictionary of organic chemistry. II. Daintith, John. XXXXXXXXX XXXXXXXXX XXXXXXXXXX Facts On File books are available at special discounts when purchased in bulk quantities for businesses, associations, institutions, or sales promotions. Please call our Special Sales Department in New York at (212) 967-8800 or (800) 322-8755. You can find Facts On File on the World Wide Web at http://www.factsonfile.com Compiled and typeset by Market House Books Ltd, Aylesbury, UK Printed in the United States of America MP 10987654321 This book is printed on acid-free paper iranchembook.ir/edu CONTENTS Preface vii Entries A to Z 1 Appendixes I. Carboxylic Acids 233 II. Amino Acids 235 III. Sugars 238 IV. Nitrogenous Bases and Nucleosides 239 V. The Chemical Elements 241 VI. The Periodic Table 243 VII. The Greek Alphabet 244 VIII. Fundamental Constants 245 IX. Webpages 246 Bibliography 247 iranchembook.ir/edu iranchembook.ir/edu PREFACE This dictionary is one of a series covering the terminology and concepts used in important branches of science. The Facts on File Dictionary of Organic Chemistry has been designed as an additional source of information for stu- dents taking Advanced Placement (AP) Science courses in high schools. It will also be helpful to older students taking introductory college courses. This volume covers organic chemistry and includes basic concepts, classes of compound, reaction mechanisms, and important named organic com- pounds. In addition, we have included a number of compounds that are im- portant in biochemistry, as well as information on certain key biochemical pathways. The definitions are intended to be clear and informative and, where possible, we have illustrations of chemical structures. The book also has a selection of short biographical entries for people who have made im- portant contributions to the field. There are a number of appendixes, in- cluding structural information on carboxylic acids, amino acids, sugars, and nitrogenous bases and nucleosides. There is also a list of all the chemical el- ements and a periodic table. The appendixes also include a short list of use- ful webpages and a bibliography. The book will be a helpful additional source of information for anyone studying the AP Chemistry course, especially the section on Descriptive Chemistry. It will also be useful to students of AP Biology. ACKNOWLEDGMENTS Contributors John O. E. Clark B.Sc. Richard Rennie B.Sc., Ph.D. vii iranchembook.ir/edu iranchembook.ir/edu A ABA See abscisic acid. temperature intervals were called degrees absolute (°A) or degrees Kelvin (°K), and abscisic acid (ABA) A PLANT HORMONE were equal to the Celsius degree. It can be once thought to be responsible for the shown that the absolute temperature scale shedding (abscission) of flowers and fruit is identical to the currently used thermody- and for the onset of dormancy in buds namic temperature scale (on which the unit (hence its early name, dormin). The com- is the KELVIN). pound is associated with the closing of pores (stoma) in the leaves of plants de- absolute zero The zero value of ther- prived of water. modynamic temperature; 0 kelvin or –273.15°C. See absolute temperature. absolute alcohol Pure alcohol (ethanol). absorption 1. A process in which a gas absolute configuration A particular is taken up by a liquid or solid, or in which molecular configuration of a CHIRAL mol- a liquid is taken up by a solid. In absorp- ecule, as denoted by comparison with a ref- tion, the substance absorbed goes into the erence molecule or by some sequence rule. bulk of the material. Solids that absorb There are two systems for expressing ab- gases or liquids often have a porous struc- solute configuration in common use: the ture. The absorption of gases in solids is D–L convention and the R–S convention. sometimes called sorption. There is a dis- See optical activity. tinction between absorption (in which one substance is assimilated into the bulk of an- absolute temperature Symbol: T A other) and ADSORPTION (which involves at- temperature defined by the relationship: tachment to the surface). Sometimes it is T = θ + 273.15 not obvious which process is occurring. where θ is the Celsius temperature. The ab- For example, a porous solid, such as acti- solute scale of temperature was a funda- vated CHARCOAL may be said to absorb a mental scale based on Charles’ law, which large volume of gas, but the process may applies to an ideal gas: actually be adsorption on the high surface αθ V = V0(1 + ) area of internal pores in the material. θ where V is the volume at temperature , V0 2. The process in which electromagnetic the volume at 0, and α the thermal expan- radiation, particles, or sound waves lose sivity of the gas. At low pressures (where energy in passing through a medium. Ab- real gases show ideal behavior) α has the sorption involves conversion of one form value 1/273.15. Therefore, at θ = –273.15 of energy into another. the volume of the gas theoretically be- comes zero. In practice substances become absorption spectrum See spectrum. solids at these temperatures; however, the extrapolation can be used for a scale of accelerator A substance that increases temperature on which –273.15°C cor- the rate of a chemical reaction. In this sense responds to 0° (absolute zero). The scale is the term is synonymous with CATALYST. It also known as the ideal-gas scale; on it is common to refer to catalysts as ‘acceler- 1 iranchembook.ir/edu acceptor ators’ in certain industrial applications. R1COR2 + R3OH ˆ CR1R2(OH)(OR3) For example, accelerators are used in the The formation of a hemiacetal is an exam- VULCANIZATION of rubber and in the poly- ple of NUCLEOPHILIC ADDITION to the car- merization of adhesives. Also, in the pro- bonyl group of the aldehyde or ketone. The duction of composite materials using first step is attack of the lone pair on the O polyester resins a distinction is sometimes of the alcohol on the (positively charged) C made between the catalyst (which initiates of the carbonyl group. This is catalyzed by the polymerization reaction) and the accel- both acids and bases. Acid catalysis occurs erator (which is an additional substance by protonation of the O on the carbonyl, making the catalyst more effective). The making the C more negative and more sus- terms promoter and activator are used in a ceptible to nucleophilic attack. In base similar way. catalysis the OH– ions from the base affect the –OH group of the alcohol, making it a acceptor The atom or group to which a more effective nucleophile. pair of electrons is donated in forming a In general, hemiacetals exist only in so- COORDINATE BOND. lution and cannot be isolated because they easily decompose back to the component accessory pigment See photosynthetic alcohol and aldehyde or ketone. However, pigments. some cyclic hemiacetals are more stable. For example, cyclic forms of SUGAR mol- ecules are hemiacetals. 12 Further reaction of hemiactals with an- other molecule of alcohol leads to a full acetal. For example: ˆ CH(OH)(CH3)(OC2H5) + C2H5OH CH(CH3)(OC2H5)2 The overall reaction of an aldehyde or ke- Acenaphthene tone with an alcohol to give an acetal can be written: R1COR2 + R3OH ˆ CR1R2(OR3) acenaphthene (C H ) A colorless crys- 2 12 10 It is also possible to have ‘mixed’ acetals talline derivative of naphthalene, used in 1 2 3 producing some dyes. with the general formula CR R (OR )- (OR4). Note that if the acetal is derived 1 2 acetal A type of compound formed by from an aldehyde, then R and/or R may reaction of an alcohol with either an al- be a hydrogen atom. The mechanism of dehyde or a ketone. The first step in for- formation of an acetal from a hemiacetal is mation of an acetal is the formation of acid catalyzed. It involves protonation of an intermediate, known as a hemiacetal. the –OH group of the hemiacetal followed For example, ethanal (acetaldehyde; by loss of water to form an oxonium ion, which is attacked by the alcohol molecule. CH3CHO) reacts with ethanol (C2H5OH) as follows: Formerly it was conventional to use the ˆ terms ‘hemiacetal’ and ‘acetal’ for com- CH3CHO + C2H5OH CH(OH)(CH3)(C2H5O) pounds formed by reaction between alde- The hemiacetal has a central carbon atom hydes and alcohols. Similar reactions (from the aldehyde) attached to a hydro- between ketones and alcohols gave rise to gen, a hydroxyl group, a hydrocarbon compounds called hemiketals and ketals. group (CH3), and an alkoxy group Current nomenclature uses ‘hemiacetal’ (C2H5O). If a ketone is used rather than an and ‘acetal’ for compounds derived from aldehyde, the resulting hemiacetal contains either an aldehyde or a ketone, but reserves two hydrocarbon groups.

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