Chapter 14 - Alcohols Flashcards
Properties of alcohols, Reaction of alcohols.
What is the functional group of alcohols?
-OH
Why do alcohols with few carbon atoms have much higher boiling points than alkanes with the same number of carbon atoms?
Alcohols have the polar O-H bond, which forms the strong hydrogen bonds between bonds so require more energy to break.
How do alcohols and alkanes compare in volatility?
Alcohols with the same number of carbon atoms as an alkane will be less volatile.
Why are alcohols soluble in water?
The polar OH bond forms hydrogen bonds with the water molecules.
As hydrocarbon chain increases, how does solubility of alcohols change?
It decreases as the OH group’s influence becomes relatively small and solubility shifts to that of alkanes.
What is a primary alcohol?
The OH group is attached to a carbon atom that is attached to two hydrogen atoms and one alkyl group.
What kind of alcohol is methanol?
Although misleading it is a primary alcohol.
Therefore, what are secondary and tertiary alcohols?
Secondary: OH attached to carbon attached to two alkyl groups
Tertiary: OH attached to carbon attached to three alkyl groups
The combustion of alcohols has what products?
Carbon dioxide and water
What is used to oxidise alcohols?
Potassium dichromate
What are the two forms of chromium in oxidation reactions?
Dichromate(VI) ions that are orange
Chromium(III) ions that are green
Which two products can be formed from the oxidation of primary alcohols?
Aldehydes or carboxylic acids
How are aldehydes prepared from the oxidation of primary alcohols?
Gentle heating of primary alcohols with acidified potassium dichromate.
What measure is taken to ensure no carboxylic acid is made?
Aldehyde is distilled out of the mixture as it forms to prevent any further reaction.
How are carboxylic acids prepared from the oxidation of primary alcohols?
Primary alcohol is heated strongly under reflux with an excess of acidified potassium dichromate.
Why is it under reflux for carboxylic acid preparation?
To ensure any aldehyde initially formed also undegoes oxidation to the carboxylic acid.
What product is formed from the oxidation of secondary alcohols?
Ketones
How are ketones prepared from the oxidation of secondary alcohols?
Heated under reflux with acidified potassium dichromate.
What product is formed from the oxidation of tertiary alcohols?
Tertiary alcohols do not undergo oxidation reactions.
What is dehydration?
Any reaction in which a water molecule is removed from the starting material.
What are the conditions of a dehydration reaction?
Alcohol is heated under reflux in the presence of concentrated sulfuric acid or phosphoric acid.
What are the products of a dehydration reaction?
An alkene and water
Alcohols react with hydrogen halides to form what?
Haloalkanes and water
What are the conditions of a halogen substitution reaction of an alcohol?
Alcohol is heated under reflux with sulfuric acid and a sodium halide, the hydrogen halide is formed in situ.
The hydrogen halide reacts with the alcohol to form a haloalkane and water
NaBr + H2SO4»_space;> NaHSo4 + H20
