Chemistry Chapter 19

Transcription

1 hemistry 2100 hapter 19

2 arboxyl Derivatives In this chapter, we study three classes of compounds derived from carboxylic acids; anhydrides, esters, and amides. Each is related to a carboxyl group by loss of H 2. H A carboxylic ac id ' An anhydride ' An ester H 2 An amide -H 2 -H 2 -H 2 -H H- ' -H H-' -H H-H 2

3 Y acyl [ acetyl = Ac: = H 3 ] H l Y = ' ' 2 carboxylic acid acid chloride anhydride ester amide

4 Esters The functional group of an ester is a carbonyl group bonded to an - group. may be alkyl or aryl. Both IUPA and common names of esters are derived from the names of the parent carboxylic acids. ame the alkyl or aryl group bonded to oxygen first, followed by the name of the acid; replace the suffix -ic acid by -ate. A cyclic ester is called a lactone. H 3 H 2 H 3 Ethyl ethanoate (Ethyl acetate) Diethyl pentanedio ate (Diethyl glutarate) A fiv e-membered lactone

5 Y + H Z Z + H Y

6 δ + δ + δ - Y δ - + H Z Z + H Y

7 δ + δ + δ - Y δ - + H Z Z + H Y

8 δ + δ + δ - Y δ - + H Z Z + H Y

9 δ + δ + δ - Y δ - + H Z ' Z + H Y

10 δ + δ + δ - Y δ - + H Z' ' Z + H Y

11 δ + δ + δ - δ - H Y + H Z' ' Z + H Y

12 δ + δ + δ - δ - H Y + H Z' + H H Y ' Z

13 Fischer esterification δ + δ + δ - δ - H Y + H Z' H + + H H Y ' Z

14 Hydrolysis of Esters H + H 3 H 2 H 3 + H 2 H 3 H + H 3 H 2 H Ethyl acetate Acetic acid Ethanol

15 Saponification H 3 H 2 H 3 Ethyl acetate ah H 2 H3 - a + heat + + Sodium hydroxide Sodium acetate H 3 H 2 H Ethanol

16 Properties of Esters ethyl butyrate pineapple octyl acetate orange H 3 H coumarin clover methyl salicylate wintergreen methyl anthranilate grape H 2 methyl anthranilate grape

17 Triglycerides & Waxess H 2 H (myristic) (oleic) H 2 (linoleic) waxes

18 eaction with Amines Esters react with ammonia and with 1 and 2 amines to form amides. H 2 H 3 Ethyl 2-phenyl acetate + H 3 H 2 + H 3 H 2 H 2-Phenylacetamide

19 Amides The functional group of an amide is a carbonyl group bonded to a nitrogen atom. To name an amide, drop the suffix -oic acid from the IUPA name of the parent acid, or -ic acid from its common name, and add -amide. If the amide nitrogen is also bonded to an alkyl or aryl group, name the group and show its location on nitrogen by - ; two alkyl or aryl groups by,-di-. H 3 H 2 Acetamide (a 1 amide) H 3 HH 3 -Methylacetamide (a 2 amide) H(H 3 ) 2,-Dimethylformamide (a 3 amide)

20 ' " ' "

21 ' " ' "

22 ' " ' "

23 ' " ' "

24 ' " ' "

25 Amides A cyclic amide is called a lactam. α β H A four-membered lactam (a β-lactam) The penicillins are referred to as β-lactam antibiotics. H The penicillins differ in the group bonded to the carbonyl carbon H 2 H A seven-membered lactam H Amoxicillin The β-lactam ring S H 3 H 3 H

26 Preparation of Amides In principle, we can form an amide by treating a carboxylic acid with an amine and removing -H from the acid and an -H from the amine. In practice what occurs if the two are mixed is an acid-base reaction to form an ammonium salt. If this salt is heated to a high enough temperature, water is eliminated and an amide forms. H 3 -H Acetic acid + H 2 H 2 H 3 Ethanamine (Ethylamine) + H H 3 H 2 H 3 An ammonium salt heat H 3 -HH 2 H 3 An amide + H 2

27 Preparation of Amides It is much more common, however, to prepare amides by treating an anhydride with an amine. H 3 --H 3 H 2 H 2 H 3 H 3 -HH 2 H 3 Acetic anhdyride An amide + + H 3 H

28 Anhydrides The functional group of an anhydride is two carbonyl groups bonded to the same oxygen. The anhydride may be symmetrical (from two identical acyl groups), or mixed (from two different acyl groups). To name an anhydride, drop the word "acid" from the name of the carboxylic acid from which the anhydride is derived and add the word "anhydride. H 3 --H 3 Acetic anhydride

29 eaction with Alcohols Anhydrides react with alcohols and phenols to give an ester and a carboxylic acid. H 3 H 3 + HH 2 H 3 H 3 H 2 H 3 + HH 3 Acetic anhydride Ethanol Ethyl acetat e Acetic acid Aspirin is prepared by the reaction of salicylic acid with acetic anhydride. H H + H 3 --H 3 Salicylic acid Acetic an hydride H H 3 Acetylsalicylic acid (Aspirin) + H 3 -H Acetic acid

30 Phosphoric Anhydrides The functional group of a phosphoric anhydride is two phosphoryl (P=) groups bonded to the same oxygen atom. H-P--P-H H H Diphosphoric acid (Pyrophosphoric acid) - -P--P Diphosphate ion (Pyrophosphate ion) H-P--P--P-H H H H Triphosphoric acid - -P--P--P Triphosphate ion

31 ATP Adenosine Triphosphate

32 Polyamides ylon-66 was the first purely synthetic fiber. It is synthesized from two six-carbon monomers. H H Hexanedioic acid (Adipic acid) remove H 2 H + H H H 1,6-Hexanediamine (Hexamethylenediamine) heat -H 2 H ylon-66 (a polyamide) H n

33 Polyamides The polyaromatic amide known as Kevlar is made from an aromatic dicarboxylic acid and an aromatic diamine. remove H 2 nh H 1,4-Benzenedicarboxylic acid (Terephthalic acid) + H H H H 1,4-Benzenediamine (p-phenylenediamine) heat -H 2 H H Kevlar (a polyaromatic amide) n

34 Polyesters The first polyester involved polymerization of this diester and diol. remove H 3 H H 3 H 3 Dimethyl terephthalate H + H 1,2-Ethanediol (Ethylene glycol) heat -H 3 H n Poly(ethylene terephthalate) (Dacron, Mylar)

35 Polycarbonates Lexan, the most familiar polycarbonate, is formed by reaction between the disodium salt of bisphenol A and phosgene.! remove a + l - H 3 + a - - a + + l l H 3 Disodium salt of Bisphenol A Phosgene -al H 3 H 3 Lexan (a polycarbonate) n