Carboxylic Acids and Their Derivatives

Transcription

1 arboxylic Acids and Their Derivatives

2 Families ontaining the arbonyl Group Family Y Z Y Z aldehyde or ketone carboxylic acid or -- ester or -- acid halide or -F,-l,-Br,-I acid anhydride or amide or -N

3 arboxylic Acid Functional Group arbonyl + hydroxyl = arboxyl General Formula: R- = R The carbonyl carbon and oxygen are sp 2 hybridized. The hydroxyl oxygen is sp 3 hybridized.

4 Sources of arboxylic Acids xidation of Primary Alcohols and Aldehydes R [] R [] R primary alcohol aldehyde carboxylic acid Substituted Benzenes as a Source of Substituted Benzoic Acids Mn4 - r Benzoic Acid

5 Nomenclature of arboxylic Acids Names of the Simplest arboxylic Acids ompound Systematic Name Trivial (ommon) Name Methanoic Acid Formic Acid 3 Ethanoic Acid Acetic Acid 32 Propanoic Acid Propionic Acid 322 Butanoic Acid Butyric Acid 3222 Pentanoic Acid Valeric Acid exanoic Acid aproic Acid eptanoic Acid Enanthic Acid Systematic Nomeclature methyl hexanoic acid β-methyl caproic acid 2 N2 2-amino-3-phenylpropanoic acid phenylalanine

6 Physical Properties of arboxylic Acids Boiling Points - igher than alcohols of similar molecular weight arboxylic acids self associate through hydrogen bonds. R R Water Solubility- More water soluble than ethers, aldehydes, ketones and alcohols of similar molecular weight arboxylic acids have three opportunities for hydrogen bonding. R

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8 Acidity of arboxylic Acids 3 2 propanoic acid water 3 2 propanoate ion hydronium ion

9 Acidity of arboxylic Acids arboxylic acids are generally stronger acids than phenols but weaker than mineral acids.

10 hemical and Physical Properties of arboxylic Acids arboxylic acids react with bases. 3 acetic acid + Na Na+ 3 sodium acetate arboxylate salts are ionic and possess much higher boiling and melting points than those of the corresponding carboxylic acids (Ionic forces are much stronger than secondary forces). Sodium acetate: MP 324, solid at room temperature Acetic acid: MP 17, liquid at room temperature

11 hemical and Physical Properties of arboxylic Acids _ Na + + Na + 2 arboxylic acids that have 6 or more carbons are only slightly soluble or insoluble in water. arboxylate salts are much more soluble than their corresponding carboxylic acids because of their ionic nature _ arboxylic acids have increased solubilities in neutral or basic environments because the acids are converted into their carboxylate ions.

12 Worksheet

13 1. Give an appropriate name for each compound. 3 a b. 3 3 l

14 2. Give structure(s) and name(s) for the major organic product(s) of the following reactions a. b l Na, 2 K, 2

15 arboxylic Acid Esters Synthesized from a carboxylic acid and an alcohol: condensation R + R + R R + 2 carboxylic acid alcohol or phenol hydrolysis ester Nomenclature base on parent alcohol and carboxylic acid: propanoic acid methanol methyl propanoate

16 Worksheet

17 arboxylic Acid Esters Additional Nomenclature examples: isobutyl acetate 3 ethyl 3-methyl pentanoate isopropyl butanoate

18 4. Give an appropriate name for each compound. a b c. F ` F 2 3 ethyl 2,4-difluoro benzoate

19 Physical Properties of Esters Ester molecules cannot hydrogen bond to each other. Therefore, esters have much lower boiling and melting points than those of carboxylic acids Propanoic acid, bp 141 Methyl acetate, bp 57 Esters are less soluble in water than are carboxylic acids because esters cannot form as many hydrogen bonds to water molecules as can carboxylic acids.

20 Physical Properties of Esters The secondary forces in esters are weaker than those in aldehydes and ketones, and thus esters have lower melting and boiling points Methyl acetate, bp 57 Butanal, bp 76 Esters have about the same water solubilities as aldehydes and ketones because all three hydrogen bond to water equally well.

21 Esters ave haracteristic dors 23 3 Pineapple Pear Apple Raspberry Rum Banana Peach range

22 Amides - Structure and lassification Subclassification R1 N R1 N R2 R1 N R2 R3 1º 2º 3º an amides engage in hydrogen bonding??

23 Amides - Structure and lassification The amide is better represented as a dipolar ion: N N Because the bond between the carbonyl carbon atom and the nitrogen atom has a partial double bond character, the bond angles about the carbonyl carbon atom and nitrogen atom are both close to 120 (sp 2 hybridization). The dipolar ion nature of the amide bond is very important in determining the structure and function of protein molecules.

24 Amides - Synthesis At low temperatures a carboxylic acid and an amine will take part in a simple acid-base reaction to form an ammonium salt. R1 + R3 N R o R1 R3 N R2 carboxylic amine ammonium acid carboxylate

25 Amides - Synthesis At a higher temperature, a condensation reaction takes place between the carboxylic acid and the amine. R1 + N >100 o R1 N + 2 carboxylic ammonia primary acid amide R1 + N R2 >100 o R1 N R2 + 2 carboxylic 1º amine secondary acid amide R1 + R3 N R2 >100 o R1 R3 N R2 + 2 carboxylic 2º amine tertiary acid amide

26 Amides - Nomenclature 3 3 N 3 2,2-dimethyl propanamide N 223 N-propyl benzamide

27 Amides - Synthesis and Nomenclature 3 + N 3 >100 o 3 N acetic acid methylamine N-methylacetamide N N aniline acetic N-phenyl acetic anhydride acetamide acid

28 N formic acid N2 N 23 benzoic acid

29 Amides - Physical Properties Amides have the strongest secondary attractive forces and the highest melting and boiling points of any covalent organic compounds. Potential ydrogen Bonds: R N N R

30 Amides - Physical Properties 3 acetic acid 3 N 3 N-methylacetamide 3 N acetamide 3 3 N 3 N,N-dimethylacetamide

31 Amides - Physical Properties The resonance structure of the amide functional group results in a large charge separation in an amide molecule resulting in large polarity and secondary attractive forces.

32 Amides - omparison to ther Families