Preview Organic Chemistry by Marye Anne Fox James K. Whitesell (1994)

Preview Organic Chemistry by Marye Anne Fox James K. Whitesell (1994) Preview Organic Chemistry by Marye Anne Fox James K. Whitesell (1994) Preview Organic Chemistry by Marye Anne Fox James K. Whitesell (1994) Preview Organic Chemistry by Marye Anne Fox James K. Whitesell (1994) Preview Organic Chemistry by Marye Anne Fox James K. Whitesell (1994)

I Marye Anne Fox James K.Whitesell A B B Periodic Table of the Elements i Group at Key IA Q atomic mass 0079 12.011 electronegativity 2.2 2.5 [He]2s 2p H i Hydrogen 6.941 901218 10 configuration C symbol II electronic name atomic number Carbon [He^s Li Lithium Be Beryllium 22.98977 24.305 1.0 1.2 [Ne]3s [Ne]3s Na 11 Mg VII 12 B III IV VB B VI VII Sodium Magnesium 39 0983 40.08 44.9559 47.88 50.9415 51.996 54.9380 55.847 0.9 1.0 1.2 1.3 1.5 1.6 1.6 1.6 [Ar]4s [Ar]4s JX 19 [Ar]3d4s Ca 20 2 [Ar]3d 4s SC [Ar)3d 4s Ti 21 22 5 V 23 Cr 24 Mn 1.7 [Ar^s [Ar]3d 4s (Ar]3d 4s 58.9332 25 Fe [Ar]3d 4s 26 CO Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt 85.4678 87.62 88.9059 91.22 92.9064 95.94 98.906 101.07 102.9055 0.9 1.0 1.1 1.2 1.2 1.3 1.4 1.4 [Krj5s [Kr)5s Rb 37 br [Kr)4d5s 38 2 [Kr]4d 5s Y [Kr]4rf ZA 39 40 [Kr]4d 5s 5s Nb 41 [Kr]4c/ MO 42 1.5 e 5s [Kr]4d 5s [Kr]4d 5s TC 43 RU 44 Rh Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium 132.9054 137.33 138.9055 178.49 180.9479 183.85 186.207 190.2 192.22 0.9 1.0 1.1 1.3 1.4 1.5 1.5 [Xe]6s [Xe]6s-' [Xe]5d6s CS 55 Ba 14 [Xe]4r La 56 57 5d 6s ,4 Hf [Xe]4f~ 72 5d 6s Ta 73 K [Xe]4/ 5d 6s W Barium Lanthanium Hafnium Tantalum Tungsten (223) 226.0254 227.0278 (261) (262) (263) 0.9 1.0 1.0 [Rn]7s [RnRs Fr 87 Ra se Radium Francium [Rn]5f"6d 7s {Rr\$d7s* tAC 89 [Rn]5f 6d 7s 5d 6s Re 75 1.6 ,4 [Xe]4f OS 5dV [Xe)4r' 76 Ir 77 Osmium Iridium 157.25 Unnilpentium Unnilhexium 140.12 140.9077 144.24 145 150.4 151.96 1.1 1.1 1.1 1.1 1.0 5d 6s Rhenium 1.1 [XeHfts 45 Unqio4 Unpio5 Unhioe Unnilquadium Actinium ,4 [Xe]4/' 74 Cesium 27 [Xe)4f 6s [Xe]4f 6s [Xe]4/ 6s [Xe]4/ 6s 1.1 [Xe]4/ 6s [Xe]4r 5d6s *Lai Ce 58 Pr 59 Nd 60 Pm 61 Sm 62 63 G(l Praseodymium Neodymium Promethium Samarium Europium 232.0381 231.0359 238.029 237.0482 (244) (243) (247) 1.1 1.1 1.2 1.2 1.2 1.2 =1.2 [Rn)6d 7s [Rnl'^ctfs [Rn)5f 6cr7s [Rn]5f6o7s [RnjSr^s Th Thorium 90 Pa Protactinium 91 U Uranium 92 Np Neptunium 93 PU Plutonium 94 Am Americium 64 Gadolinium [RnJSrVs t Actinides EU Cerium [Rn]5r 95 6d7s Cm Curium 96 A Noble Gases The elements shown in color commonly are those that 4.0026 undergo bonding with carbon 1s He III A IV Helium 20.179 12.011 14.0067 15.9994 18.9984 2.5 3.1 3.5 4.1 [He]2s 2p B 26.9815 1.5 [He]2s 2p N [He]2s 2p O F 30.97376 32.06 35.453 39.948 1.7 2.1 2.4 2.8 Si H [Ne]3s 3p P [Ne]3s 3p D ,5 CI 16 Chloride Argon 83.80 74.9216 78.96 79.904 1.8 1.8 1.7 1.8 2.0 2.2 2.5 2.7 [Ar]3d'°4s [Ar]3d'°4s 28 CU 29 ,0 [Ar)3d Zll 30 4s 4p VJcl [Ar]3d'°4s 31 4p Ge [Ar]3d 32 Germanium ,0 AS Nickel Copper Zinc Gallium 106.4 107.868 112.41 114.82 ,18.69 121.75 1.4 1.4 1.5 1.5 1.7 1.8 [Kr]4d'° [Kr]4d ,0 Pd 46 5s [Kr]4d Ag 47 ,0 5s Cd 48 In [Kr]4d'°5s 5p 49 [Ar]3d'°4s 4p Sn [Kr)4d 50 ,0 Se 33 [Ar]3d'°4s 34 5s 5p Sb 4p Br ~5 [Ar]3d ,0 Kr 127.60 126.9045 131.30 2.2 5s 5p Te [Kr]4d ,0 5s 5p 52 53 [Kr]4d ,0 Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon 196.9665 200.59 204.37 207.2 208.9804 (209) (210) (222) 1.4 1.5 1.4 14 5d 6s Pt [Xe]4r" 78 AU [Xe]4f 79 5d'°6s Hg Tb 65 6s Dy ee 173.04 174.967 1.1 ,2 HO [Xe]4f 6s 67 Er Holmium Erbium ,3 [Xe]4f 6s 68 Tm 259 260 (257) (258) =1.2 =1.2 Bk Berkelium 97 V^I Californium [Rn]5/"7s 98 ES Einsteinium [Rn]5f 99 ,2 7s Fm Fermium [Rn]5f' 100 7s Mdioi Mendelevium [Rn]5/' 7s NO Nobelium [Rn]5f 102 Lu Lutetium (254) 70 ,4 Lr [Xe]4/' 5d At Astatine 5d6s Ytterbium =1.2 7s Yb [Xe]4/' Thulium (251) ,0 [Xe]4f 6s 69 84 1.1 14 6p PO 1.1 =1.2 [Rn]5f 83 168.9342 (247) Bi 4 [Xe)4i" 5o"°6s 167.26 =1.2 [Rn]5f*7s 82 1.1 [Xe]4f""6s Dysprosium Terbium Pb 1.1 1.1 ,0 8, ,0 5s 5p 54 2.0 1.8 [Xe]4f 5d 6s 6p 164.9304 162.50 1.1 [Xe]4/ Tl Polonium 158.9254 80 1.7 [Xe]4r5d'°6s 6p Bismuth Mercury 6s 6s 6p [Xel4^' 5cf' Lead Gold Thallium Platinum [Xe]4/ 1.6 1.4 ,4 ,0 5d 6s 36 Xe 195.09 (Xe]4/ 2.0 10 is 4s 4p Krypton [Kr]4d 51 Bromine Selenium Arsenic 2 [Kr]4d'°5s 5p 4s 4p Ar Sulfur 72.59 Ni ,7 Phosphorus 69.72 2 10 [Ne]3s 3p Silicon 65.38 Aluminum 63.546 Ne 28.0855 [Ne]3s 3p Neon 2 [He]2s 2p Fluoride 58.70 [Ar]3d 4s Oxygen ,3 Nitrogen [Ne]3s 3p Al [He]2s 2p , Carbon 2 C Boron [Ne]3s 3p MB VII 10.81 IB VIA 2.0 [He]2s 2p VA A 71 6d7s 103 Lawrencium ,0 6sV 85 ,4 [Xe]4f ,0 5d 6s 6p Rn Radon se ORGANIC CHEMISTRY Reproduction of a woodblock print, in the authors' collection, from a book published in 1497 in Basel, Switzerland, depicting an alchemist (standing at the right) and his two assistants, one working at the "fume hood" and the other taking a sample from the cask The alchemist is holding a retort, an all-in-one distillation apparatus in which the long snout serves as the condenser (Another retort is in use in the fume hood, the floor.) and a third one is on ORGANIC CHEMISTRY Marye Anne Fox James K Whitesell The University of Texas Austin, Texas Jones and Bartlett Publishers Boston London Editorial, Sales, Jones and and Customer Service Offices Bartlett Publishers One Exeter Plaza 02116 Boston, 617-859-3900 800-832-0034 MA Jones and Bartlett Publishers International PO Box 1498 London W6 7RS England © 1994 by Jones and Bartlett Publishers, Inc All rights reserved No part of the material protected by this copyright notice be reproduced or utilized in any form, electronic or mechanical, including Copyright may photocopying, recording, or by any information storage and retrieval system, without written permission from the copyright owner Library of Congress Cataloging-in-Publication Data Fox, Marye Anne, 1947Organic chemistry / Marye Anne Fox, James K Whitesell cm p Includes bibliographical references and index ISBN 0-86720-207-6 Biochemistry Chemistry, Organic II I Whitesell, James K Title QD251.2.F69 547— dc20 1994 93-43800 CIP David E Phanco Developmental Editor: Patricia Zimmerman Production Editor: Judy Songdahl Manufacturing Buyer: Dana L Cerrito Acquisitions: Arthur C Bartlett, Design: Nancy Blodget Illustrations: Typesetting: Sarah Mittelstadt Bean The Clarinda Company Cover Design: Marshall Henrichs Printing and Binding: Rand McNally Cover Printing: John P Pow Company Cover: Opiate drugs such as morphine are effective in relieving pain because they bind to the same site in the central nervous system as the enkephalins The image on the cover is of crystals of an enkephalin, viewed between crossed polarizers so as to bring out the vivid rainbow display of colors (Photograph © Dr Dennis Kunkel/Phototake NYC) Printed in the United States of America 10 98 97 96 95 94 Brief Contents Bonding Chapter Structure and Chapter Alkenes, Arenes, and Alkynes in Alkanes 21 Chapter Functional Groups Containing Heteroatoms Chapter Chromatography and Spectroscopy Chapter Stereochemistry Chapter Understanding Organic Reactions 193 Chapter Mechanisms of Organic Reactions 227 109 155 Chapter Nucleophilic Substitutions at sp -Hybridized Carbon 267 Chapter Elimination Reactions Chapter 10 Chapter 11 303 Electrophilic Addition to Bonds 59 Carbon-Carbon Multiple 331 Electrophilic Substitution of Aromatic Molecules 69 Chapter 12 Addition and Substitution by Heteroatomic 401 Nucleophiles at sp -Hybridized Carbon Chapter 13 Addition and Substitution by Carbon Nucleophiles 451 sp -Hybridized Carbon Chapter 14 Skeletal-Rearrangement Reactions Chapter 15 Multistep Syntheses 505 Chapter 16 Polymeric Materials 541 Chapter 11 Structures and Reactions of Naturally Occurring Compounds Containing Oxygen Groups 581 477 Functional at vi Brief Contents Chapter 18 Structures and Reactions of Naturally Occurring Compounds Containing Nitrogen Groups Functional 613 Chapter 19 Noncovalent Interactions and Molecular 651 Recognition Chapter 20 Catalyzed Reactions Chapter 21 Cofactors for Biological Chapter 22 Energy Storage Chapter 23 Molecular Basis for Drug Action in 681 Redox Reactions Organic Molecules 713 745 789 94 Chapter Functional Groups Containing Heteroatoms that this reaction takes place by hydrolysis, the addition of water, not by treatment with a redox reagent The addition of water across a carbon-carbon double bond results in an alcohol This addition reaction does not shift the oxidation levels of hydro- gen or oxygen in water at all However, a hydrogen atom is added to one carbon of the alkene (as a consequence, that carbon is reduced), whereas addition of the OH group to the other carbon is an oxidation These two same molecule, reduction and oxidation, exactly balance one another, and no overall change in oxidation level of the molecule occurs when water is added to an alkene processes in the H — OH " H Acid > " These two examples show, as we have seen before, that the presence of a multiple bond between carbon atoms means that the carbons are at a higher oxidation level than in an alkane and that a n bond changes the oxidation level of a molecule to the same extent as does the introduction of a single bond to a heteroatom 3-11 Sulfur-containing Compounds Oxygen and S^ fore H R A thlcl /S\ sulfur are in the same column of the periodic table and therehave similar valence electronic requirements Like oxygen, sulfur forms hybrid orbitals that participate in covalent bonding For example, when sulfur is bound to one carbon, in analogy with the oxygen in an alcohol, a thiol is formed When sulfur is bonded to two alkyl or aryl carbons (in analogy to bonding to oxygen alkyl sulfide A thioether the A in an ether), the functional thiol ester is a compound in group is called a thioether or which an SR group replaces QR grQup m aR ester O R^^SR' A thiol DIMETHYL SULFOXIDE: A VERSATILE SOLVENT ester Dimethyl sulfoxide (DMSO) is an odorless dipolar aprotic organic solvent with unusual properties By virtue of its highly polarized sulfur-oxygen bond, DMSO is miscible with water but also quite soluble in other, less-polar organic solvents Furthermore, it passes readily through the skin and will even carry with it other organic molecules It was considered a possible way to deliver drugs to the blood stream for compounds that are destroyed in the digestive system This application of DMSO has not been commercialized, in part because of concern about possible toxic side effects of the solvent itself Another complication is that DMSO is reduced in the body to methyl sulfide, a compound with a highly disagreeable odor O Reduction HC CH Dimethyl sulfoxide (DMSO) H C^ CH Methyl sulfide Aromatic Compounds Containing Heteroatoms Many thioethers of the chemical properties of thiols and alcohols and of and ethers are similar Most of the significant differences these functional groups result because sulfur's valence shell is between the third Thus, 3s and 3p atomic orbitals are used to form sulfur's hybrid atomic orbitals These third-level orbitals are significantly larger than those of the second level, and a size mismatch in the overlap between carbon and sulfur results in a weaker carbon-sulfur covalent bond than that between carbon and oxygen In addition, sulfur's electronegativity is significantly lower than that of oxygen (2.5 versus 3.5), and it is more polarizable Finally, because sulfur, in the third row of the periodic table, has access to 3d orbitals, its valence shell can be expanded beyond eight electrons: sulfur often participates in bonding with more than four atoms As a result, the chemistry of sulfur compounds is somewhat more complex than that of oxygen For example, sulfonic acids and their derivatives have no analogy in oxygen chemistry This expanded valence capability also makes possible amidelike derivatives of sulfonic acids Some sulfonamides are potent antibacterial substances known as the sulfa drugs, which are frequently used in medicine level EXERCISE 3-P A thiol ester is analogous is an ester except that the singly bonded oxygen a thiol ester 10 be more or less acthan a simple ester toward nucleophilic attack at the carbon end of the double bond? Explain your reasoning replaced by sulfur tive to Would you expect C^O Aromatic Compounds Containing Heteroatoms 3-12 We know from Chapter that planar, cyclic, conjugated molecules containing 4n + electrons {n = an integer) are aromatic compounds that have unAromatic molecules in which one or more carbon atoms are replaced by heteroatoms are heteroaromatic compounds These compounds have a stability similar to that of their all-carbon analogs usual stability Heteroaromatic Molecules Many aromatic molecules contain nitrogen, oxygen, sulfur, or other heteroatoms in the ring As a family, they are called heterocyclic aromatics, or heteroaromatics, because the heteroatom is one of the component atoms of the cyclic array These compounds have common, rather than systematic, names Three such compounds that contain five ring atoms are shown in Figure 3-35 (on page 96): furan, pyrrole, and thiophene Each of these heterocycles can be represented by the cyclic array shown at the left in Figure 3-35, in which one lone pair of electrons on the heteroatom is held in a p orbital perpendicular to the molecular plane and, hence, aligned for conjugative interaction with the p orbitals of the carbon-carbon double bonds These structures are analogous to the cyclopentadienyl anion (Figure 2-20) because each contains six electrons in a planar cyclic delocalized k system, making them Hiickel aromatics In this geometry, the nitrogenhydrogen bond of pyrrole must project in the atomic plane and be orthogonal to the n system This position is occupied by a lone pair in both furan and thiophene, as shown in the left-hand structure in Figure 3-35 Section 3-12 95 O R— S — OH II II O A sulfonic acid O II R— S— NH, II O A sulfonamide 96 Chapter Functional Groups Containing Heteroatoms Q Q Q H Furan A FIGURE Pyrrole Thiophene 3-35 Representative heteroaromatic molecules A FIGURE 3-36 Several representations of pyridine As shown in Figure 3-36, there are also aromatics For example, we can write ture of pyridine In these structures, six-membered heteroatomic Kekule-like contributors for the struc- we find a cyclic, delocalized, six-elec- tron system just like that in benzene In contrast with pyrrole, in which the is part of the n system, the lone pair on nitrogen in pyridine is contained in an sp orbital in the plane of the six ring atoms and is orthogo- lone pair nal to the p orbitals EXERCISE 3-Q Both pyridine and pyrrole have lone pairs on nitrogen that can be protonited in an acid-base reaction In view of Hiickel's rule, which protonation will be easier? That is, will pyrrole or pyridine be the stronger base? Explain your reasoning w // N I H N i } N I H Imidazole Pyridine o •A H H Pyrrole A heterocyclic aromatic can contain more than one heteroatom, and each structure shown in the margin represents a five- or a six-membered ring containing two nitrogen atoms Three biologically important bases, — Aromatic Compounds Containing Heteroatoms caffeine: a heteroaromatic stimulant compound containing nitrogen, is present in both tea has a dramatic stimulating effect on people, and both tea Caffeine, a cyclic and and coffee It have been consumed for centuries for this effect In this been marketed by itself and in combination with other ingredients for use as a stimulant by those who not like coffee or when drinking a beverage is not convenient Until recently, the caffeine sold in this way was prepared by adding a methyl group to theobromine, a related compound obtained from cocoa fruits (Theobromine is also present in tea.) coffee century, caffeine has CH However, the relatively large Theobromine Caffeine demand for decaffeinated coffee has re- by extraction from coffee beans At first, halogenated organic solvents were used to remove the caffeine from the bean, but concern about possible adverse effects of these solvents on health has stimulated the development of an alternate process that uses steam or supercritical carbon dioxide sulted in large quantities of caffeine being available uracil, thymine, and cytosine, are hydroxy or amino derivatives of pyrimi- dine (Figure 3-37) Heteroatoms are also found in fused-ring molecules (structurally similar to the polycyclic aromatic hydrocarbons) Figure 3-38 shows three common fused structures quinoline, pteridine, and purine as well as two — O NH «^ NH H Uracil FIGURE Thymine Cytosine 3-37 Biologically important derivatives of pyrimidine OH Quinoline A FIGURE Pteridine Purine 3-38 Representative fused-ring heteroaromatics Guanine NH, Adenine Section 3-12 97 98 Chapter Functional (.roups Containing Heteroatoms OH NH, Phenol Aniline A FIGURE 3-39 Three-dimensional representations of orbital interaction in aniline and phenol with sp -hybridized heteroatoms purine derivatives, guanine and adenine Purines are subunits of biologically important systems Guanine and adenine, together with uracil, thymine, and cytosine, are aromatic bases and are components of nucleotides, which constitute the chemical basis for genetic coding a subject discussed in Chapter 22 Many different derivatives of pteridine have been — isolated from insects and are responsible for the bright and varied colors in butterfly wings Heteroatom-substituted Arenes In addition to the heteroaromatics, ring, a number of important which have a heteroatom present compounds have in the a heteroatom attached to an all-carbon aromatic ring Because the ring contains only carbon atoms, such compounds are not called heteroaromatics For example, as shown in Fig2 ure 3-39, sp hybridization of nitrogen and oxygen in aniline and phenol would produce the optimal geometry for the overlap of a lone pair in a het- eroatomic p orbital with the aromatic array of p orbitals on carbon in the ring, although overlap of electrons from the heteroatom with the ring n sys- even without rehybridization We shall see the effect of this extended conjugation on the chemical reactivity of aromatic compounds in Chapter 10 From Chapter 2, we know that aromatic rings can have alkyl sub- tem can also take place It is also possible for these alkyl substituents to bear heteroatoms Several of these compounds are encountered frequently and are usually referred to by common names: for example, benzoic acid, ben- stituents, as in toluene zaldehyde, acetophenone, and anisole O 0^o„ Benzoic acid 0^„ Benzaldehyde ^X c„_ Acetophenone g OCH, Anisole Alkyl Halides Section 3- 99 13 EXERCISE 3-R by the zwitterionic resonance structures for aniline shown below make aniline a stronger or a weaker base than it would be if its structure could be described simply by the resonance contributor at the left? Explain your reasoning Will contribution Mi, — < > H+ © % 3-13 > < Mi Alkyl Halides column on the right-hand side of the periodic table (before the inert gases) contains the halogens The atomic st/ucture of fluorine is shown in Figure 3-40 Fluorine requires only one o bond to satisfy its va- The F: next-to-last drogen by fluorine and a single electron to satisfy the valence requirements of is ' Four s/? -hybrid orbitals both atoms, making H — Fa A FIGURE 3-40 Mixing of atomic orbitals in fluorine to form sp -hybridized e @ H-'F: is W r1 contributed by hy- stable molecule The o bond 2s 2Pi v lence requirement In the structure of hydrofluoric acid, seven valence electrons are contributed ls H — F: orbitals +-> H — F: nonetheless highly polarized because there difference in electronegativity between hydrogen and is a substantial fluorine Carbon-fluorine bonds are otherwise similar to carbon-nitrogen or carbon-oxygen bonds, as in methyl fluoride .o H C-F: H C — F: H C— F: CHEMICALLY INERT CARBON-FLUORINE BONDS An important distinction between the bond between fluorine and carbon and other bonds to carbon is its much greater strength For example, a C-F bond is 25% stronger than a C-H bond As a result, fluorocarbons are unusually stable, and polymers such as Teflon, in which there are only C-F and C-C bonds, are almost completely inert to chemical reaction, except with strong reducing agents They can therefore be used for applications where other organic materials are degraded, such as in coatings for heating utensils or as seals for containers of corrosive liquids Chapter 100 FIGURE Functional Groups Containing Heteroatoms 3-41 CH, Isomeric butyl fluorides CH CH CH CH 2 CH CHCH CH F 1-Fluorobutane primary alkyl halide) (a (a HC 2-Fluorobutane secondary alkyl halide) — C — CH 2-Fluoro-2-methylpropane (a tertiary alkyl halide) Like alcohols, alkyl fluorides can be primary, secondary, or tertiary (Figure 3-41) Other alkyl halides have carbon bonded to one of the other halogen atoms (chlorine, bromine, or iodine) and have structures similar to those of alkyl fluorides They can be named either as halogenated alkanes (for example, bromoethane) or as alkyl halides (for example, ethyl bromide) From the bond-dissociation energies of alkyl fluorides, chlorides, bromides, and iodides (while keeping the alkyl group constant), we conclude that the o bond becomes weaker as the difference in size between carbon and the halogen increases (Figure 3-42) In the progression from the top to the bot- tom of the periodic table, the electronegativity of the halogen decreases, and hence its ability to respond to charge demand (polarThe stability of the anion (with the negative charge on I~ spread over a much larger area than on F") also is important Therefore, heterolytic cleavage within a series of alkyl halides also becomes easier in the progression from alkyl fluorides to alkyl iodides, and the rates of C-X heterolytic cleavage increase as the R-X bond becomes weaker (Figure 3-43), in parallel to the acidities of HX whereas the size izability) increases EXERCISE 3-S Remembering that the dipole moment of a molecule is the vector sum of its bond dipoles, predict whether a dipole moment will exist in any of the following multihalogen-substituted compounds and draw (in three dimensions) the direction of the dipole: (a) CC14 (b) CHCI3 nr H3C-F -> — H C— nr H C— HC 3 FIGURE CH2C12 Br -» (d) - CH,- CH CH3C1 FIGURE 3-43 - AH° = 85 kcal/mole Br- AH = 70 kcal/mole AH° = 57 kcal/mole I- 3-42 cleavage in alkyl halides R— R—PCl R— Br R— — — — CBr Cl Bond-dissociation energies in methyl halides Relative rates of heterolytic (e) AH° = 108 kcal/mole CH, CH Cl A (c) @ > R > R @ @ R @ R + F Slowest + Cl° + Br + I Fastest Nomenclature Nomenclature 3-14 Each heteroatom-containing functional group considered in this chapter is named in accord with the IUPAC rules presented in Chapter 1, except that the suffix is changed to identify the functional group Table 3-7 (pages 102 and 103) is a summary of the suffixes used to name these families This table also includes the minimal representation needed to characterize each of the functional groups considered Like hydrocarbons, these compounds are named by locating the longest continuous carbon chain that contains the functional group The root designates the number of carbons and the suffix designates the functional group Substituents are assigned numbers to indicate their positions along the carbon skeleton The frequent occurrence of low-molecular-weight members of some made it convenient to use common names, rather nomenclature, to name them For example, formaldehyde functional groups has than the IUPAC (HCHO), acetaldehyde (CH CHO), acetyl for CH CO (CH3COOH), and acetone (CH3COCH3) are used almost to conventional — , acetic acid the exclusion of IUPAC names EXERCISE 3-T Write acceptable names for each of the following compounds: OS (d) X OH o O o (g) ^ H (e)H C.X"NT CH ,CH (h) cr- NH «) x ex EXERCISE 3-U Draw acceptable structures corresponding to each of the following names: (a) butanone (b) 2-hexanone (c) 3-pentanone (d) 4-methylpentanal (e) 2-chloropropanoic acid (f) methyl propanoate (g) dimethylamine (h) propanoamide (i) butanoyl chloride (j) ethyl 2-bromopropanoate IUPAC Section 3-14 101 102 Table 3-7 Functional Groups Containing Heteroatoms Chapter Nomenclature of Various Functional Groups Functional Group Composition Alcohol R IUPAC — OH Suffix -anol Example CH CH OH Ethanol Ether R —O— alkyl ether — O— CH CH 3 Methyl ether O Aldehyde O -anal II II /C R ^H H HC Ethanal O Ketone O -anone II II R R CH CH CH H 3C 2 2-Pentanone O Carboxylic acid o -anoic acid II OH R^ OH HC Ethanoic acid O Acid chloride O -anoyl chloride II II R HC CI CI Ethanoyl chloride O Amide O -anoamide II R II NH ^^ NH Propanoamide H N-Methyl propanoamide Conclusions By considering the electronic structures of nitrogen, oxygen, and fluorine (and atoms in the same columns of the periodic table), we can make important predictions about their derivatives with respect to bond strength, molecular geometry, and reactivity with nucleophiles and electrophiles This analysis helps us to understand the reactivity of these functional groups and to recognize oxidation and reduction levels among organic compounds containing heteroatoms The molecules into subgroups based upon the degree of substitution of the heteroatom-bearing carbon, except in amines for which the level of substitution on nitrogen is used instead Thus, the terms primary, secondary, and tertiary applied to alcohols, is classification of heteroatom-containing X R 103 Conclusions Table 3-7 Nomenclature of Various Functional Groups Functional Group < IUPAC Composition Anhydride O O II II O R (continued) Example Suffix -anoic anhydride O O II II R Propanoic anhydride O Ester O alkyl -anoate II R HC OR' OCH3 Methyl ethanoate RNH Amine , RjNH, R3N H C— NH— CH CH3 alkylamine Methyl ethylamine R— CN Nitrile CH CH2CN -anonitrile Propanonitrile R— C = NH Imine CFLCH,C -anal imine 1 H H = NH Propanal imine Thioether R— S — CH 3SCH 2CH alkyl thioether Methyl ethyl thioether (methyl ethyl sulfide) Alkyl halide ethers, and R— alkyl halides refer to the number haloalkane CH 3CH F or alkyl halide Fluoroethane of carbon substituents carbon bearing the oxygen or halogen substituent these same designations refer to the number (ethyl fluoride) When applied on the to amines, of alkyl groups attached to ni- trogen Heteroatoms alter the structure of carbon compounds because the presence of one or more lone pairs of electrons on an atom of liigher electronegativity induces significant partial charge separation within the molecule The heteratom usually functions as a locus for chemical activity; that is, as the functional group in a molecule Reactions of heteroatom-containing compounds usually take place at bonds to or near the heteroatom The difference in electronegativity between carbon and a heteroatom (X) to which it is bound results in polarization of the C-X o~ bond In many cases, the vectorial sum of such polar covalent bonds causes a net molecular dipole moment, which has consequences for the molecule's physical properties (greater reactivity toward charged reagents, higher melting points and boiling points, higher solubility in polar solvents, and so forth) The presence of a dipole moment within a molecule makes that molecule subject to attack by nucleophiles and electrophiles Nucleophiles attack molecules at centers of partial positive charge, whereas electrophiles attack at centers of partial negative charge 104 Chapter Functional Groups Containing Heteroatoms A heteroatom bound to both carbon and a hydrogen can participate in hydrogen bonding This interaction derives from polarization of the X-H bond so that hydrogen is attracted to a lone pair of a heteroatom in another molecule or at another site within the same molecule Hydrogen bonding has an important effect on the three-dimensional structure of a molecule (if intramolecular) and on solvation and intermolecular association (if intermolecular) Bond cleavages molecules can be accomplished in homolytic or heterolytic pathways In a bond homolysis, the two electrons initially shared between the two atoms in a covalent bond are partitioned equally to the two radical fragments In the alternative pathway, heterolytic cleavage, in organic both electrons of the covalent bond are transferred to one of the participating atoms, leaving the other atom with none of the electrons of the bond Radicals result from homolytic cleavage, whereas ions result from heterolytic bond cleavage Multiple bonding between carbon and nitrogen (double bond) and and oxygen is nitriles (triple found is possible, as in imines bond) Double bonding between carbon in aldehydes, ketones, carboxylic acids, esters, amides, or other derivatives of carboxylic acids Because oxygen's valence shell is with two bonds (and two lone pairs of electrons), triple bonds to oxygen are not found in stable molecules, except in carbon monoxide Alcohols are functional groups bearing oxygen o bound both to carbon and to hydrogen A characteristic reaction of alcohols is the acid-catalyzed loss of water, the first step of which generates an oxonium ion from which water is lost to form a carbocation The reactivity of an alcohol is dependent on the character of the carbon atom to which the OH group is attached Carbocations (formed by heterolytic cleavage) and radicals (formed by homolytic cleavage) follow the same relative order of stability: benzyl ~ tertiary > secondary ~ allyl > primary > methyl This order of stability arises filled from the greater polarization of a highly substituted carbon and from resonance stabilization and greater hyperconjugation by alkyl groups The Lucas test can be used to chemically distinguish primary, secondary, and tertiary alcohols by the rates at which they undergo conversion into alkyl halides Ethers lack the OH group of alcohols and are therefore much less reac- than alcohols Their primary use in organic chemistry is as polar aprotic inert solvents Carbonyl groups are highly polarized so that carbon bears appreciable partial positive charge, making it a potential site for nucletive ophilic attack Sulfur-containing The chemistry compounds are similar to those containing oxygen and thioethers are have some of the features of carboxylic acid esters, but because of mismatch in orbital size between the sulfur and the adjacent carbon, the carbon-sulfur n bond in the zwitterionic resonance contributor is considerably weaker than the carbon-oxygen n bond Enhanced reactivity toward nucleophilic attack at carbon results from this weaker interaction Aromaticity is maintained in the presence of heteroatoms, and the of thiols is similar to that of alcohols, similar to ethers Thiol esters same considerations regarding the number of electrons delocalized in a sta- bilized aromatic ring apply Several heteroaromatic more than one heteroatom compounds containing are important in nucleic acid chemistry Alkyl halides contain highly polar carbon-X bonds Often such compounds have high dipole moments and are readily attacked by nucleophilic reagents at the partially positively charged carbon 105 Review Problems Nomenclature IUPAC atoms heteroatom-containing of rules discussed in Chapter 2: compounds follows the number of carbon roots designate the in the longest chain containing the functional group; suffixes desig- nate the identity of the functional group; and numbers and positions of substituents are represented by prefixes and Arabic numerals of New Reactions Summary Protonation of Amines Catalytic Hydrogenation of Aldehydes, © R3N + HA R3 ^= N— H + A" Ketones, and Imines O Alcohol Oxidation R X High pressure H R^ ^H O H OH R X /\ H OH H,,Pt K [0] R x H OH ^ X R^ R O R' X /-\ R R High pressure , Alcohol Substitution: Lucas Test N HCl R— OH R— CI -* 3°>2°>r ^H II H NH V ^£1* ZnCl, Alcohol Dehydration H R— OH © 3°>2°>1° R + HX> > K Heat alkene Review Problems 3-1 Like alkenes, imines Draw mers the cis and CH, can exist as geometric isotrans isomers of ethanal Would you expect interconversion of these isomers to be easier or harder than the cis-trans isomerization of 2-butene? imine [3jZ Classify the following alcohols primary, secondary, or tertiary pound according to the and amines as each com- Name IUPAC rules NH, (c) 3-3 Ethers, esters, aldehydes, and thioethers solve in concentrated sulfuric acid dis- Why? 3-4 Environmentalists are greatly concerned about ^N , imperils these species OH (b) o an atmospheric ozone hole centered on Antarctica and thought to be caused in part by the presence of fluorochlorocarbons in the atmosphere Ozone, absorbs high-energy ultraviolet light (which is dangerous to plant and animal life), and its absence H (a) OH (d) OH (a) Draw a Lewis dot structure of ozone, being sure to indicate formal charge on each atom 3, 106 Chapter (b) By drawing a resonance structure, explain how the two O-O bonds in ozone are of equiv- 3-13 Write structural formulas that correspond to alent length (a) From (c) Functional Groups Containing Heteroatoms oxygen atoms in you have drawn, predict the hybridization of the the structure that the following descriptions: C4H8 two aldehydes with the formula C H g O a secondary alcohol with the formula C H three ketones with the formula C H 10 O a tertiary amine with the formula C4HUN four esters with the formula (b) (c) whether ozone is linear or bent (d) The 3-5 due to the high conjugate base derived by deproto- acidity of a sulfonic acid stability of the is Write significant resonance nation of the acid monoanion of benzene sulfonic acid (C H S0 H), and use them to explain why the (e) a (f) structures for the acidity of sulfonic acids is higher than that of car- boxylic acids 3-6 Explain moment (fi tertiary bromide with the formula alkyl C H9Br 3-14 Dimethyl sulfoxide (H 3CSOCH often , called DMSO), methylene chloride (CH 2C1 ), dimethylformamide [HCON(CH ) called DMF], methanol, ethyl ether (CH CH 2OCH CH 3/ often simply called (CH ) ether), and tetrahydrofuran called , why iodomethane has a smaller dipole = 1.62 D) than fluoromethane (|i = 1.85 THF] D) are common — — , organic solvents Classify each of these solvents as dipolar aprotic, polar protic, or resonance structures to explain why formaldehyde has a larger dipole moment than methanol 3-7 Use nonpolar Identify the structural feature in each molecule from which its solvent classification de- rives 3-8 Calculate the formal oxidation level of carbon 3-15 Identify each of the following reagents as a in nucleophile or an electrophile: (a) ethyne (b) acetonitrile (c) ethyl Explain amine why to ethane (CH CN) is the catalytic hydrogenation of ethyne (a) triethylamine (b) hydroxide ion (c) Fe (d) methanethiol, 3+ CH3SH called a reduction 3-16 Identify the functional group in each of the Although ethyl ether has a substantially higher molecular weight than ethanol, ethanol has the 3-9 following compounds Does the molecule act as a Lewis acid or base? higher boiling point Explain 3-10 Derivatives of butane can be obtained by the replacement of C-H bonds with C-Cl bonds when butane is exposed to chlorine gas in the presence of CFL Determine (a) how many different monochlorobutanes are possible? (b) how many ultraviolet light dichlorobutanes? O how many trichlorobutanes? (c) H,C (b) 3-11 Draw structures of all — S— OH «