CH223 Part 5/6: Carboxylic Acids & Derivatives and Enolate Chemistry (Conceptual)

Question 1

What does a acid-catalyzed esterification reaction do?

Answer 1

changes carboxylic acid to ester

Question 2

Why does an acid-catalyzed esterification reaction need an acid?

Answer 2

it protonates the carboxylic acid and makes the carbonyl group more electrophilic so that it can be attacked by even alcohols

Question 3

What are hydroxy acids?

Answer 3

compounds that contain both hydroxyl and carboxylic acid functional groups

Question 4

What do hydroxyl acids form?

Answer 4

cyclic esters called lactones

Question 5

When does intramolecular esterification take place spontaneously?

Answer 5

when a five- or six-membered ring can be formed

Question 6

What is a hydrolysis reaction the reverse of?

Answer 6

ester esterification

Question 7

Which hydrolysis reaction is irreversible? Why?

Answer 7

base-catalyzed ester hydrolysis because the NaOR base will continue to react with the product in an acid-base mechanism

Question 8

Describe the reactivity trend of common carboxylic acid derivatives?

Answer 8

acyl chloride > acid anhydride > ester > amide

Question 9

Why is acyl chloride the most reactive?

Answer 9

acyl chloride is very unstable because Cl is incredibly electronegative (won’t stable partial positive carbonyl)

Question 10

Why are acid anhydrides more reactive than esters?

Answer 10

the singular middle oxygen in an acid anhydride has to stabalize both carbonyls

Question 11

Why are esters more reactive than amides?

Answer 11

the oxygen of an ester is more electronegative than the oxygen of a nitrogen

Question 12

How can acyl chlorides be made?

Answer 12

by treating carboxylic acids with thionyl chloride (SOCl2)

Question 13

What is the role of pyridine in nucleophilic acyl substitutions with acyl chloride

Answer 13

pyridine can act as a nucleophile and catalyze a reaction to be more reactive than acyl chloride

Question 14

What is a “N” amide?

Answer 14

A substituted amide formed during a reaction of an ester with an amine

Question 15

What bond is very strong in amides?

Answer 15

the CN bond

Question 16

Why do amides have such high boiling points?

Answer 16

they have strong hydrogen bonding and dipole dipole intermolecular forces

Question 17

Are acid or base amide hydrolysis reactions irreversible?

Answer 17

both! the ammonium ion formed during the acid reaction is not nucleophilic while the carboxylate anion formed during the base reaction is not electrophilic

Question 18

What is it called when aldehydes and ketones become enols?

Answer 18

tautomerize

Question 19

What is the keto form?

Answer 19

double bond between carbon and oxygen

Question 20

What is the enol form?

Answer 20

double bond between two carbons

Question 21

Where are is the keto form reactive?

Answer 21

it is electrophilic at the carbonyl carbon

Question 22

Where is the enol form reactive?

Answer 22

it is nucleophilic at the alpha carbon

Question 23

Why does alpha-halogenation only occur once?

Answer 23

Cl is an EWG that slows down protonation enough to stop a 2nd halogentation

Question 24

What is the o-enolate?

Answer 24

there the double bond is between two carbons with a negative charge on the oxygen

Question 25

Where is the most acidic hydrogen on an ketone/aldehyde/ester?

Answer 25

the alpha halogens due to the inductive effective and resonance stabilization with the enolate

Question 26

What do enolates usually act as in reactions?

Answer 26

nucleophiles

Question 27

What do you have to make sure matches when using esters?

Answer 27

the alkoxide bases should match the ester to avoid ester saponification

Question 28

Reactions with alkoxide bases favor the ____.

Answer 28

reactants

Question 29

Reactions with LDA favor the ____.

Answer 29

products

Question 30

Where does LDA remove a proton from?

Answer 30

the less substituted alpha carbon because of steric crowding

Question 31

What reaction occurs when enolates react with carbonyls of aldehydes and ketones?

Answer 31

aldo condensation

Question 32

When an aldo reaction is heated, what is the product?

Answer 32

an alpha, beta unsaturated carbonyl compound

Question 33

When will intramolecular aldol condensation reactions occur?

Answer 33

when five- or six-membered rings can be formed

Question 34

In mixed aldol reactions, how do you know which one is the nucleophile and which one is the electrophile?

Answer 34

• the nucleophile has an enolizable hydrogen
• aldebydes are always more electrophilic than ketones

Question 35

What is a Claisen condensation reaction?

Answer 35

when two esters react to form a beta keto ester

Question 36

What must be true of the ester involved in a claisen condensation?

Answer 36

must have at least two alpha hydrogens (two enolates formed)

Question 37

When will intramolecular Claisen condensation (dieckmann cyclization) occur?

Answer 37

when a five- or six- membered ring can be formed

Question 38

What can aldehydes, ketones, and ester enolates be alkylated with?

Answer 38

primary alkyl halides

Question 39

How can you avoid polyalkylations of enolates?

Answer 39

use an enamie as a enol equivalent or use LDA

Question 40

What is the micheal reaction?

Answer 40

the addition of enols/enolates to the best carbon

Question 41

What is the product of a micheal reaction?

Answer 41

1,5 diketone