17.3 2 Preparations and reactions of carboxylic acids

Question 1

How are carboxylic acids formed

Answer 1

Oxidation of primary alcohol or aldehyde oxidising agent of acidified potassium dischromate heat mixture under reflux
when oxidation is complete reaction is fractionally distilled to obtain a pure sample of carboxylic acid

Question 2

Preparation by hydrolysis

Answer 2

Nitrites are organic molecules containing the CN
Hydrolysed by heating under reflux with either a dilute acid or aqueous alkali
the same apparatus of preparation and purification
C triple N bond breaks

Question 3

acidic hydrolysis

Answer 3

get NH4+ also forming-see equations in the book

Question 4

alkaline hydrolysis

Answer 4

NH3 AND get salt ion that if add dilute acid will form carboxylic acid

Question 5

Reduction

Answer 5

Can be reduced to primary alcohols but not aldehydes this is because aldehydes are more easily reduced than carboxylic acids so an aldehydes formed would be immediately reduced to a primary alcohol
Use lithium tetrahydrioaluminate
solvent of dry ether
formation of water

Question 6

Neutralisation

Answer 6

mix with aqueous alkali 
carboxylate salts
RCOONa
sodium ethanoate used in hand warmers and salt and vingar crips 
are ionic the salts

Question 7

Halogenation

Answer 7

OH replaced by halogen atom
functional group becomes COCl
acyl chlorides that are highly reactive
reagent is phosphorus (V) chloride
anhydrous conditions reagent+ acyl chloride react with water
reaction is vigrous no heating required
see equation in book

Question 8

Acyl chlorides

Answer 8

named using -oyl chloride RCOCl

Question 9

Halogenation inorganic products

Answer 9

phosphorus trichloride oxide mixes with the acyl chloride has to be separated by fractional distillation
Hydrogen chloride gas escapes as misty fumes

Question 10

Esterification

Answer 10

carboxylic acid is mixed with an alcohol and small amount of acid catalyst often concentrated sulphuric
acid
even though use a catalyst the reaction is still slow and reversible

Question 11

Where are esters found

Answer 11

Used in industry as solvents and making polymers (polyesters) . Common in nature responsible for smell of fruits and many animal fats and vegetable oils are esters