Ch 8 - Carboxylic Acids

Question 1

What are carboxylic acids?

Answer 1

• contain a carbonyl and a hydroxyl group connected to the same carbon
• always terminal groups

Question 2

How are carboxylic acids indicated?

Answer 2

• with the suffix -oic acid

- salts are named with the suffix -oate, and dicarboxylic acids are -dioic acids

Question 3

What are the physical properties of carboxylic acids?

Answer 3

• polar and H bond very well, resulting in high bp (often exist as dimers)
• enhanced acidity by the resonance between its oxygen atoms

Question 4

How can the acidity of carboxylic acids be affected?

Answer 4

• enhanced by substituents that are electron withdrawing (highly electronegative)
• decreased by substituents that are electron donating

Question 5

How are carboxylic acids made?

Answer 5

• by the oxidation of primary alcohols or aldehydes using an oxidizing agent likt KmnO4, dichromate sates, or chromium trioxide

Question 6

What is a nucleophilic acyl substitution?

Answer 6

• a nucleophile attacks the electrophilic carbonyl carbon, opening the carbonyl and forming a tetrahedral intermediate
• the carbonyl reforms, kicking off the leaving group

Question 7

What happens if the nucleophile in a nucleophilic acyl substitution is ammonia or an amine?

Answer 7

an amide is formed

• amides are given suffix -amide
• cyclic amides are called lactams

Question 8

What happens if the nucleophile in a nucleophilic acyl substitution is an alcohol?

Answer 8

an ester is formed

• esters are given the suffix -oate
• cyclic esters are called lactones

Question 9

What happens if the nucleophile in a nucleophilic acyl substitution is another carboxylic acid?

Answer 9

an anhydride is formed

- both linear and cyclic anhydrides are given the suffix -anhydride

Question 10

How are carboxylic acids reduced?

Answer 10

• by primary alcohol with strong reducing agent like LiAlH4
• aldehyde intermediates are formed, but are also reduced to primary alcohols
• NaBH4 is a common reducing agent for other organic reactions, but not strong enough to reduce a carboxylic acid

Question 11

How do beta-dicarboxylic acids and other beta-keto acids undergo spontaneous decarboxylation?

Answer 11

• when heated, losing a carbon as carbon dioxide

- this reaction proceeds via a 6-membered cyclic intermediate

Question 12

How is soap made and what is the process called?

Answer 12

• mixing long-chain carboxylic acids (fatty acids) with a strong base results in the formation of a salt (soap) through saponification

Question 13

What are the characteristics of soaps?

Answer 13

contain hydrophilic carboxylate heads and hydrophobic alkyl chain tails

Question 14

What do soaps do?

Answer 14

• organize in hydrophilic environments to form micelles
• a micelle dissolves nonpolar organic molecules in its interior and can be solvated with water due to its exterior shell of hydrophilic groups

Question 15

What is the most acidic proton on a carboxylic acid?

Answer 15

the hydroxyl hydrogen, however, in 1,3-dicarbonyls, the alpha-hydrogens is also quite acidic

Question 16

What are nucleophilic acyl substitutions favored by?

Answer 16

• favored in basic solutions, making the nucleophile more nucleophilic
• favored in acidic solutions, making the electrophile more electrophilic
• favored by good leaving groups, made by weak bases