Chap 18 Carboxylic acids and their derivatives. nucleophilic substitution at the acyl carbon 18.1 Introduction The carboxyl group,-COOH,-CO2H, is one of the most widely occurring functional groups in chemistry and biochemistry. Not only are carboxylic acids themselves important, but the carboxyl group is the parent group of a large family of related compounds
Chap 18. Carboxylic acids and their derivatives. Nucleophilic substitution at the acyl carbon 18.1 Introduction The carboxyl group, -COOH, -CO2H, is one of the most widely occurring functional groups in chemistry and biochemistry. Not only are carboxylic acids themselves important, but the carboxyl group is the parent group of a large family of related compounds
All of these carboxylic acid derivatives contain the acyl group, RCO- As a result, they are often called acyl compounds. They are called carboxylic acid derivatives R Cl Acyl (or acid) chloride r NH2 Amide (酰氯) (酰胺) R R Acid anhydride R (酸酐) NR(x-取代酰胺) R o—R Ester (酯) R NRR"(N,N-二取代酰胺)
All of these carboxylic acid derivatives contain the acyl group, RCO-. As a result, they are often called acyl compounds. They are called carboxylic acid derivatives. R O Cl R O O O R R O O R Acyl (or acid) chloride Acid anhydride Ester R O NH2 R O NHR' R O NR'R'' Amide （ 酰 胺 ） （ 酰 氯 ） （ 酸 酐 ） （ 酯 ） （ N-取 代 酰 胺 ） （ N,N-二 取 代 酰 胺 ）
18.2 Nomenclature and physical properties 18.2A Carboxylic acids HCOOH CH3 COOH Methanoic acid Ethanoic acid Formic acid) (Acetic acid) (甲酸)(蚁酸) (乙酸) 654321 ChrCHChchchbcooh CH3CH=CHCH, CH2COOH CH 3 4-Hexenoic acid 4-Methylhexanoic acid (4-己烯酸) (4-甲基己酸)
18.2 Nomenclature and physical properties 18.2A Carboxylic acids CH3 CH2 CHCH2 CH2 COOH CH3 4-Methylhexanoic acid 4 3 2 1 CH3 CH=CHCH2 CH2 COOH 6 5 4 3 2 1 4-Hexenoic acid HCOOH CH3 COOH Methanoic acid Ethanoic acid (Formic acid) (Acetic acid) （ 甲 酸 ） （ 蚁 酸 ） （ 乙 酸 ） （ 4-甲 基 己 酸 ） （ 4-己 烯 酸 ）
CICHCOOH CI3CCOOH CH3 (CH2)3CO2H Chloroethanoic acid Trichloroethanoic acid Pentanoic acid (氯代乙酸) (三氯代乙酸) (戊酸) COOH COOH COOH Benzoic acid 1-Naphthoic acid 2-Naphthoic acid (1-萘酸) (2-萘酸)
ClCH2 COOH Chloroethanoic acid （ 氯 代 乙 酸 ） Cl 3 CCOOH Trichloroethanoic acid （ 三 氯 代 乙 酸 ） CH3 (CH2 ) 3 CO2 H Pentanoic acid （ 戊 酸 ） （ 1-萘 酸 ） COOH COOH COOH Benzoic acid 1-Naphthoic acid 2-Naphthoic acid （ 2-萘 酸 ）
18.2C Acidity of carboxylic acids Most unsubtituted carboxylic acids have Ka values in the range of 10-4-10-(pka=4-5) COoH CooNa t Naoh t ho Benzoic acid(pKa=4.15) Sodium benzoate (苯甲酸钠) (water insoluble) (water soluble co2H+ NaHCO3— -CO2Na CO2 H20
18.2C Acidity of carboxylic acids Most unsubtituted carboxylic acids have Ka values in the range of 10-4—10-5 (pka = 4-5). COOH + NaOH COONa + H2O Benzoic acid Sodium benzoate (water insoluble) (water soluble) （ 苯 甲 酸 钠 ） CO2H + NaHCO3 CO2Na + CO2 + H2O (pKa = 4.15)
If carboxylic acids have electron withdrawing groups, they are stronger than unsubstituted acids Cl H CH-C-CO2H>CH-C-cC0 H)>C1--C--C0OH> C-CO,H H pKa 0.7 148 285 4.75 由于氯原子电负性比碳大,氯原子表现出拉电子 诱导效应( inductive effect),使羧酸容易电离出质子(H)。 羧酸的酸性增强
If carboxylic acids have electronwithdrawing groups, they are stronger than unsubstituted acids. Cl Cl C Cl CO2H Cl Cl C H CO2H H Cl C H CO2H H H C H CO2H pKa 0.7 1.48 2.85 4.75 由于氯原子电负性比碳大，氯原子表现出拉电子 诱导效应(Inductive effect)，使羧酸容易电离出质子(H+ )。 羧酸的酸性增强
CH3CH2CHC—0H>CH3CHCH2C—oH CHCH2CH2C—0H Cl Cl Cl 2-Chlorobutanoic acid 3-Chlorobutanoic acid 4-Chloro butanoic acid 285 4.05 4.50 氯原子的诱导效应随着距离的增长对羧 基的影响减弱,因而羧酸的酸性变弱。 COOH COOH COOH COOH NO c
pKa 2.85 4.05 4.50 CH3CH2CHC OH O Cl CH3CHCH2C OH O CH2CH2CH2C OH Cl Cl O 2-Chlorobutanoic acid 3-Chlorobutanoic acid 4-Chlorobutanoic acid 氯原子的诱导效应随着距离的增长对羧 基的影响减弱，因而羧酸的酸性变弱。 COOH COOH COOH COOH NO2 Cl CH3
18.2E Esters The names of esters are derived from the names of the alcohol (with the ending -yl)and the acid(with the ending -ate or -oate) CH3COCH,CH CH3COCH-CH2 CH3 CH2 COC(CH3)3 Ethyl acetate or Vinyl acetate or tert-Butyl propanoate ethyl ethanoate ethenyl ethanoate 乙酸乙酯 丙酸叔丁酯 乙酸乙烯酯 CH3COCH2,CH(CH3)2 CH3, CH2CH2C--OCH2CH2CHCH3 Isopentyl acetate (used in synthetic apple flavor) cK Isopentyl pentanoate (used in synthetic banana flavor) 乙酸异戊酯 戊酸异戊酯
18.2E Esters The names of esters are derived from the names of the alcohol (with the ending –yl) and the acid (with the ending –ate or –oate). CH3COCH2CH3 O CH3CH2COC(CH3 ) 3 O CH3COCH=CH2 O Ethyl acetate or ethyl ethanoate Vinyl acetate or ethenyl ethanoate tert-Butyl propanoate 乙 酸 乙 酯 乙 酸 乙 烯 酯 丙 酸 叔 丁 酯 CH3COCH2CH2CH(CH3 ) 2 O CH3CH2CH2CH2C O OCH2CH2CHCH3 CH3 Isopentyl acetate (used in synthetic banana flavor) Isopentyl pentanoate (used in synthetic apple flavor) 乙 酸 异 戊 酯 戊 酸 异 戊 酯
c—ocH c—ocH3 Methyl benzoate Methyl p-chlorobenzoate 苯甲酸甲酯 对-氯苯甲酸甲酯 HOoCCH, COOH CHCHOoCCH CH Malonic acid Diethyl malonate 丙二酸 丙二酸二乙酯
C O OCH3 C O Cl OCH3 Methyl benzoate Methyl p-chlorobenzoate 苯 甲 酸 甲 酯 对 -氯 苯 甲 酸 甲 酯 HOOCCH2 COOH CH3 CH2 OOCCH2 COOCH2 CH3 Malonic acid Diethyl malonate 丙 二 酸 丙 二 酸 二 乙 酯
18.2F Carboxylic anhydrides (酸酐) Most anhydrides are named by dropping the word acid from the name of the carboxylic acid and then adding the word anhydride H3C—C H2C—C Hc—C H3C c HC Acetic anhydride Succinic anhydride Maleic anhydride Phthalic anhydride 乙酐 环丁酐 环丁烯酐 邻苯二甲酸酐 马来酐
18.2F Carboxylic anhydrides （酸酐） Most anhydrides are named by dropping the word acid from the name of the carboxylic acid and then adding the word anhydride. C O O O H3C H3C C O O O H2C H2C O O O C O O O HC HC Acetic anhydride Succinic anhydride Maleic anhydride Phthalic anhydride 乙 酐 环 丁 酐 环 丁 烯 酐 马 来 酐 邻 苯 二 甲 酸 酐