File

advertisement

Alcohol & Phenol Reactions

Alcohol Reactions

1. Dehydration - elimination of water water is eliminated from adjacent carbon atoms and a second bond is formed between the 2 carbon atoms uses a large amount of alcohol and a small amount of acid (H

2

SO order of reactivity:

4

) as the catalyst

– tertiary > secondary > primary

Dehydration Examples

1. Dehydrate butanol.

2. Dehydrate 2-butanol.

3. Dehydrate 2-methyl-2-butanol.

2. Halide Substitution alcohols react with concentrated hydrohalogens (HCl, HBr, HF) to be converted into alkyl halides competes with the elimination reaction

(dehydration) but this reaction is favored using a large excess of concentrated acid

(HCl and zinc chloride) we can distinguish between 1

°

, 2

° and 3° alcohols by their different rates of reaction using the Lucas Test order of reactivity:

– tertiary > secondary > primary

Halide Substitution Examples: The Lucas Test

1. Primary alcohols - are not converted to alkyl chlorides at room temp; dissolve completely

2. Secondary alcohols – dissolves, but within 5 minutes, the alkyl chloride separates out

3. Tertiary alcohols – react immediately; the insoluble tertiary alkyl chloride separates out as a cloudy layer

3. Esterification – alcohols react with carboxylic acids to form esters and water esters – compounds in which the proton of an acid is replaced by an organic group

General formula is

Esters are named as derivatives of BOTH the carboxylic acid and the alcohol

The 1 st

word denotes the alcohol group (R) and is named like a hydrocarbon with a –yl ending

The 2 nd

word is derived from the name of the parent acid, with the “-ic acid” ending changed to an “-ate” ending.

Esterification Examples

Ex.1 React methanol with acetic acid.

Ex.2 React propanol with butanoic acid.

Ex.3 React 2-propanol with butanoic acid.

4. Oxidation - the most important method of preparing aldehydes, ketones and carboxylic acids from alcohols

aldehyde ketone carboxylic acid

Uses Jones Reagent in what is called the

Bordwell-Wellman Test

Jones Reagent – made by dissolving CrO water with H

2

SO

4

to give chromic acid, which is orange in color

3

in

Oxidation Examples

Primary alcohols - oxidized in a 2-step process to first give an aldehyde, and then an acid

Ex.; Oxidize ethanol.

Secondary alcohols - oxidized to form ketones

Ex.; Oxidize 2-butanol.

Tertiary alcohols - have no C-H bonds on the hydroxyl carbon, therefore they cannot undergo oxidation.

Ex.; Oxidize tert-butanol.

Reactions of Phenols

Phenols DO NOT undergo dehydration or substitution reactions because it is very hard to break the C-O bond when the carbon atom is part of an aromatic ring

They will form esters because the O-H bond is breaking, not the C-O bond

1. Esterification - phenol reacts with an acid anhydride (two acid molecules with a water removed) to form a carboxylic acid and an ester

Ex.; part a : form acetic anhydride part b : react phenol with acetic anhydride

2. Oxidative Coupling - uses potassium ferricyanide, K

3

Fe(CN)

6

, as the catalyst

-three types of coupling: ortho-ortho, ortho-para, and para-para

Ex. React phenol with K

3

Fe(CN)

6.

Ex. React p-methylphenol with K

3

Fe(CN)

6.

Download