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 (H2SO4) as the catalyst
• order of reactivity:
– 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 1st word denotes the alcohol group (R) and
is named like a hydrocarbon with a –yl ending
– The 2nd 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 CrO3 in
water with H2SO4 to give chromic acid,
which is orange in color
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, K3Fe(CN)6, as the catalyst
• -three types of coupling: ortho-ortho,
ortho-para, and para-para
• Ex. React phenol with K3Fe(CN)6.
• Ex. React p-methylphenol with K3Fe(CN)6.