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1、CHAPTER 20 CARBOXYLIC ACID DERIVATIVES: NUCLEOPHILIC ACYL SUBSTITUTION SOLUTIONS TO TEXT PROBLEMS 20.1(b)Carboxylic acid anhydrides bear two acyl groups on oxygen, as in . They are named as derivatives of carboxylic acids. (c)Butyl 2-phenylbutanoate is the butyl ester of 2-phenylbutanoic acid. (d)In
2、 2-phenylbutyl butanoate the 2-phenylbutyl group is an alkyl group bonded to oxygen of the ester. It is not involved in the acyl group of the molecule. CH3CH2CH2COCH2CHCH2CH3 O C6H5 2-Phenylbutyl butanoate CH3CH2CHCOCH2CH2CH2CH3 O C6H5 Butyl 2-phenylbutanoate CH3CH2CHCOCCHCH2CH3 O O C6H5C6H5 CH3CH2C
3、HCOH O C6H5 2-Phenylbutanoic acid2-Phenylbutanoic anhydride RCOCR O O 536 BackForwardMain MenuTOCStudy Guide TOCStudent OLCMHHE Website CARBOXYLIC ACID DERIVATIVES: NUCLEOPHILIC ACYL SUBSTITUTION537 (e)The ending -amide reveals this to be a compound of the type . (f)This compound differs from 2-phen
4、ylbutanamide in part (e) only in that it bears an ethyl sub- stituent on nitrogen. (g) The -nitrile ending signifi es a compound of the type RCN containing the same number of carbons as the alkane RCH3. 20.2The methyl groups in N,N-dimethylformamide are nonequivalent; one is cis to oxygen, the other
5、 is trans. The two methyl groups have different chemical shifts. Rotation about the carbonnitrogen bond is required to average the environments of the two methyl groups, but this rotation is relatively slow in amides as the result of the double-bond character im- parted to the carbonnitrogen bond, a
6、s shown by these two resonance structures. 20.3(b)Benzoyl chloride reacts with benzoic acid to give benzoic anhydride. (c)Acyl chlorides react with alcohols to form esters. The organic product is the ethyl ester of benzoic acid, ethyl benzoate. ?C6H5CCl O Benzoyl chloride CH3CH2OH Ethanol ?C6H5COCH2
7、CH3 O Ethyl benzoate HCl Hydrogen chloride ?C6H5CCl O Benzoyl chloride C6H5COH O Benzoic acid ?C6H5COCC6H5 O O Benzoic anhydride HCl Hydrogen chloride C H O N CH3 CH3 ? ? C H O N CH3 CH3 2-Phenylbutanenitrile CH3CH2CHCN C6H5 CH3CH2CHCNHCH2CH3 O C6H5 N-Ethyl-2-phenylbutanamide CH3CH2CHCNH2 O C6H5 2-P
8、henylbutanamide RCNH2 O BackForwardMain MenuTOCStudy Guide TOCStudent OLCMHHE Website 538CARBOXYLIC ACID DERIVATIVES: NUCLEOPHILIC ACYL SUBSTITUTION (d)AcyltransferfrombenzoylchloridetothenitrogenofmethylamineyieldstheamideN-methyl- benzamide. (e)In analogy with part (d), an amide is formed. In this
9、 case the product has two methyl groups on nitrogen. (f)Acyl chlorides undergo hydrolysis on reaction with water. The product is a carboxylic acid. 20.4(b)Nucleophilic addition of benzoic acid to benzoyl chloride gives the tetrahedral intermediate shown. Dissociation of the tetrahedral intermediate
10、occurs by loss of chloride and of the proton on the oxygen. (c)Ethanol is the nucleophile that adds to the carbonyl group of benzoyl chloride to form the tetrahedral intermediate. ?C6H5CCl O Benzoyl chloride CH3CH2OH EthanolTetrahedral intermediate C6H5COCH2CH3 OH Cl ?C6H5COCC6H5 O O Benzoic anhydri
11、de HCl Hydrogen chloride Tetrahedral intermediate C6H5COCC6H5 O H Cl O ?C6H5CCl O Benzoyl chloride C6H5COH O Benzoic acid C6H5COCC6H5 HO Cl O Tetrahedral intermediate ?C6H5CCl O Benzoyl chloride H2O Water ?C6H5COH O Benzoic acid HCl Hydrogen chloride ?C6H5CCl O Benzoyl chloride 2(CH3)2NH Dimethylami
12、ne ?C6H5CN(CH3)2 O N,N-Dimethylbenzamide (CH3)2NH2 Cl? ? ?C6H5CCl O Benzoyl chloride 2CH3NH2 Methylamine ?C6H5CNHCH3 O N-Methylbenzamide ? CH3NH3 Cl? BackForwardMain MenuTOCStudy Guide TOCStudent OLCMHHE Website In analogy with parts (a) and (b) of this problem, a proton is lost from the hydroxyl gr
13、oup along with chloride to restore the carbonoxygen double bond. (d)The tetrahedral intermediate formed from benzoyl chloride and methylamine has a carbon nitrogen bond. The dissociation of the tetrahedral intermediate may be shown as More realistically, it is a second methylamine molecule that abst
14、racts a proton from oxygen. (e)The intermediates in the reaction of benzoyl chloride with dimethylamine are similar to those in part (d). The methyl substituents on nitrogen are not directly involved in the reaction. Then ?C6H5CN(CH3)2 O N,N-DimethylbenzamideDimethylammonium chloride (CH3)2NH2 Cl? ?
15、 C6H5CN(CH3)2 O H Cl (CH3)2NH ?C6H5CCl O Benzoyl chloride (CH3)2NH DimethylamineTetrahedral intermediate C6H5CN(CH3)2 OH Cl ?C6H5CNHCH3 O N-MethylbenzamideMethylammonium chloride ? CH3NH3Cl?C6H5CNHCH3 O H Cl CH3NH2 ?C6H5CNHCH3 O N-Methylbenzamide HCl Hydrogen chloride Tetrahedral intermediate C6H5CN
16、HCH3 O H Cl ?C6H5CCl O Benzoyl chloride CH3NH2 MethylamineTetrahedral intermediate C6H5CNHCH3 OH Cl ?C6H5COCH2CH3 O Ethyl benzoate HCl Hydrogen chloride Tetrahedral intermediate C6H5COCH2CH3 O H Cl CARBOXYLIC ACID DERIVATIVES: NUCLEOPHILIC ACYL SUBSTITUTION539 BackForwardMain MenuTOCStudy Guide TOCStudent OLCMHHE Website (f)Water attacks the carbonyl group of benzoyl chloride to form the tetrahedral intermediate. Dissociation of the tetrahedral intermediate occurs by loss of chloride and t
