Reactions of alcohols Flashcards
Can alcohols be comusted?
alcohols burn completely to carbon dioxide and water if there is enough oxygen available
What is methylated spirits?
used in picnic stoves
ethanol with a small percentage of poisonous methanol added to make it unfit to drink
in this way it can be sold without the tax which is levied on alcoholic drinks
a purple dye is also added to show that it should not be drunk
What is an elimination reaction? What occurs in the case of alcohols?
where a small molecule leaves the parent molecule
always water in alcohols
made from the -OH group and a hydrogen atom from the next carbon to the -OH group
How are alcohols dehydrated?
with excess hot concentrated sulfuric acid
or
by passing their vapour over heated aluminium oxide
or phosphoric acid
What is the mechanism for the dehydration?
- a lone pair of electrons from the partially negative oxygen atom are transferred to a H+ ion
- then a electron from a hydrogen in the molecule is transferred to the C - C bond and an electron from the C - O bond is transffered to the positive oxygen
- this forms a double and releases water and a H+ ion
What are primary alcohols oxidised into?
aldehydes, can be further oxidised to carboxylic acids
C2H5OH + [O] (alcohol in excess - no reflux) → CH3CHO + [O] (oxidising agent in excess - reflux) → CH3COOH
What are secondary alcohols oxidised into?
ketones, R2CO
ketones are not oxidised further
CH3CHOHCH3 + [O] → CH3COCH3 + H2O
What are tertiary alcohols oxidised into?
are not easily oxidised
this is because oxidation would need a C-C bond to break, rather than a C-H bond (which is what happens when an aldehyde is oxidised)
ketones are not oxidised further for the same reason
What are the properties of many aldehydes and ketones?
pleasent smells
draw how dehydration is done in the lab
