Alcohol Reactions

Question 1

Which one is more acidic a primary or tertiary alcohol?

Answer 1

A primary alcohol because it has less steric hinderance.

Question 2

If you react a primary alcohol with an oxidizing agent such as chromic acid, what will the product be?

Answer 2

A carboxylic acid, because this oxidizing agent is too strong and it oxidizes the OH straight to COOH.

Question 3

What oxidizing agents are used to oxidize a secondary OH?

Answer 3

PCC, chromic acid, DMSO/Et3N, (COCl)2

Question 4

What happens when you oxidize a primary alcohol vs. a secondary alcohol?

Answer 4

Primary –> aldehyde
Secondary –> ketone

Question 5

What happens when you oxidize a tertiary alcohol?

Answer 5

No reaction

Question 6

A tertiary alcohol is more likely to undergo a (SN1/SN2) reaction.

Answer 6

SN1

Question 7

Possible oxidizing agents for:
Primary OH –> aldehyde

Answer 7

PCC, DMP, DMSO and COCl2 together

Question 8

What reagents can we use to create this product?

Answer 8

HCl or SOCl2 & pyridine

Question 9

What is the stereochemical outcome of this reaction?

Answer 9

inversion of configuration

Question 10

In a reaction between SOCl2 and OH, what atom is the electrophile, what atom is the nucleophile?

Answer 10

The nucleophile is the O in OH, the electrophile is the S in SOCl2.

Question 13

What is the most stable carboxylic acid derivative? Why?

Answer 13

An amide; the nitrogen in the amide acts as an electron donating group does donating electrons to the carbonyl group and making it less reactive.

Question 14

What is the least stable/most reactive carboxylic acid derivative?

Answer 14

acid halide

Question 15

Explain the general mechanism of a nucleophilic acyl substitution.

Answer 15

1. Nucleophile attacks carbonyl group, pushing double bond up as electrons on O.
2. Double bond between C and O reforms, causing ejection of LG.

Question 16

What is the reagent PCC used for?

Answer 16

It is an oxidizing agent, which is used to oxidize a primary OH into an aldehyde.

Question 17

In order to create an ester, what reactants do we need? What is the name of this mechanism?

Answer 17

An alcohol and a carboxylic acid under acidic conditions. (Cannot be performed under basic conditions.) The mechanism is Fischer esterification.

Question 18

Why are alcohols converted into tosylates?

Answer 18

Tosylates make better leaving groups which can undergo SN2 reactions. This allows secondary OHs to only undergo SN2 w/o worrying about potential carbocation rearrangements.

Question 19

What are the first steps of the mechanism between an alcohol and tosylate?

Answer 19

The O in the alcohol attacks the electrophilic S, forming a covalent bond between O and S.

Question 20

What is the stereochemical outcome in converting an OH to OTs?

Answer 20

Retention of configuration

Question 21

What is the purpose of the pinacol rearrangement?

Answer 21

It is used to convert a 1,2 diol into a ketone under acidic conditions.

Question 22

Explain the mechanism of pinacol rearrangement.

Answer 22

1. One OH group is protonated, become H2O
2. H2O leaves, forming + carbocation
3. Methyl or hydride shift occurs from the other C hydroxyl group
4. • charge moves onto the hydroxyl group + double bond forms to make a carbonyl
5. Carbonyl is deprotonated forming a ketone

Question 23

Which alcohol is more readily oxidized? Straight chain primary alcohol or phenol

Answer 23

Phenols undergo oxidation more readily than primary or secondary OHs

Question 24

General EWGs to know

Answer 24

Question 25

General EDGs to know

Answer 25

*Alkyl groups

Question 26

EWGs (increase/decrease) acidity of carboxylic acids.

Answer 26

increase by removing electron density the conjugate base is more stabilized.

Question 27

EDG (increase/decrease) the acidity of carboxylic acids. Why?

Answer 27

decrease because they add electron density, thus destabilizing the conjugate base.