Alcohols react with metallic sodium to form
hydrogen and a solution of an alkoxide ionic salt
alcohol + sodium
===> an alkoxide + hydrogen gas
Normal 'hydrogen' gas fizzing is observed
at a moderate rate, and the salt
product is soluble in the alcohol itself e.g.
ethanol + sodium ===> sodium
ethoxide + hydrogen
2CH3CH2OH + 2Na
There is some similarity with the
reaction of sodium with water (Alkali
Metals chemistry) and with a non-aqueous liquid acid like
(ii) sodium + water ==> sodium
hydroxide + hydrogen
2Na + 2H2O
2Na+OH– + H2
(iii) sodium + ethanoic acid
===> sodium ethanoate + hydrogen
2CH3COOH + 2Na
All three reactions give hydrogen
gas, though the sodium reacts very fast with water and pretty fast with
pure ethanoic acid.
hydroxide and ethanoate are similar because on evaporation of the unreacted ethanol,
water or acid, a solid white ionic compound is formed.
It can further be noted that
relatively 'unreactive' alkanes do not react with sodium.
similarly with other alcohols ...
(i) methanol + sodium ===> sodium
methoxide + hydrogen
2CH3OH + 2Na ===> 2CH3O–Na+
(iii) propan-1-ol + sodium ==> sodium
propoxide + hydrogen
+ 2Na ===> 2CH3CH2CH2O–Na+
(iv) butan-1-ol + sodium ==> sodium
butoxide + hydrogen
+ 2Na ===> 2CH3CH2CH2CH2O–Na+
When alkoxides are mixed with water, the
alkoxide salt is hydrolysed, the alkoxide ion is a strong base and
removes a proton from water.
e.g. sodium ethoxide +
water ===> ethanol + sodium hydroxide
+ H2O ===> CH3CH2OH
+ Na+ + OH-
So the final mixture will be very
Esters are another homologous
series of organic compounds (dealt with in detail on another page)
e.g. using a little conc.
sulfuric acid catalyst, and refluxing the mixture
(i) Ethyl ethanoate, an
ester, is formed by the
of carboxylic acid and an alcohol e.g.
ethanoic acid + ethanol
ethyl ethanoate + water
sometimes more simply written as
CH3COOH + CH3CH2OH
CH3COOCH2CH3 + H2O
General word equation:
carboxylic acid + alcohol
ester + water
This is a reversible reaction, so does not go
to completion. When the equilibrium point is reached, you have also
reached the point of maximum yield, and, you get about 2/3
conversion of the acid and alcohol reactants to the ester product.
acid + butan-1-ol
butyl butanoate + water
acid + propan-1-ol
propyl pentanoate + water
Esters are used in perfumes and
food flavourings. Lots of details
in section 10b. for the ..
Procedure for preparing
an ester, uses of esters, details of esters & carboxylic acids