ch14 Flashcards
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?
ensures that any aldehyde formed initially in the reaction also undergoes oxidation to the carboxylic acid.
What product is formed from the oxidation of secondary alcohols?
Secondary alcohols oxidise only
to ketones
How are ketones prepared from the oxidation of secondary alcohols?
heat under reflux with oxidising mixture. is required. dichromate goes orange to green
What product is formed from the oxidation of tertiary alcohols?
tertiary alcohols do not undergo oxidation reactions
What is dehydration?
This is the removal of a water molecule from an alcohol. The
OH and H come from neighbouring carbons.
What are the conditions of a dehydration reaction?
heat the alcohol under reflux with concentrated phosphoric or sulphuric acid.
What are the products of a dehydration reaction?
alkene (and water?)
Alcohols react with hydrogen halides to form what?
haloalkanes
