Carboylic Acids

Question 1

functional group

Answer 1

C=O
|
OH

Question 2

general formula of carboxylic acids

Answer 2

CnH2n+1COOH

n= 0,1,2,3…

Question 3

properties of carboxlic acids

Answer 3

1. all acids up to 10 C atoms are colourless liquids
2. the first 4 carboxylic acids are soluble in water due to hydrogen bonding
3. the simpler carboxylic acids tend to dimerize when in the vapour state and when dissolved in non-polar solvents
   the dimer is formed due to 2 hydrogen bonds being formed between a pair of molecules

Question 4

methods of preparing acids

Answer 4

1. oxidation of primary alcohols
2. organic nitriles

Question 5

oxidation of primary alcohols

Answer 5

this reaction is done by heating the primary alcohol with acidified potassium dichromate

RCH2OH +2(O) —>RCOOH +H2O

Question 6

organic nitriles

Answer 6

carboxylic acids can be obtained by the hydrolysis of a nitrile
this is done by heating the nirile under reflux with H2SO4

RCN –> RCOOH

Question 7

Negative inductive effect

Answer 7

the carboxylic acids can be made into stronger acids by introducing halogen atoms on the C atom adjacent to the COOH group

the halogen atoms are electronegative and they pull electrons towards themselves. This sets up a series of electron withdrawal away from the OH group
results in:
OH becoming weaker
H atom becoming morepositive

Question 8

reaction with PCl5 or SOCl2

Answer 8

the carboxylic acids have anOH group; hence they react with PCl5 or SOCl2
the Cl replaces the Oh group and the HCL fumes are produced

Question 9

what organic compound is formed when carboxylic acids are reacted with PCl5 and SOCl2

Answer 9

acyle chloride

Question 10

esterification reaction

Answer 10

carboxylic acid + alcohol –> ester + water

reaction is done by mixing the carboxylic acid and the alcohol
a small amount of concentrated H2SO4 is used as a catalyst and the mixture is heated

Question 11

isotopic labelling

Answer 11

during the esterification reaction, the acid loses OH and the alcohol loses; hence in the ester linking group, one O atom comes from the acid and one comes from the alcohol

Question 12

hydrolysis of an ester

Answer 12

esters can be hydrolysed by heating with an acid or an alkali

during these reactions, the C-O single bond of the ester linking group is broken

Question 13

acid hydrolysis

Answer 13

done by heating the ester with HCl or H2SO4
he ester is broken up into an acid or alcohol

Question 14

alkaline hydrolysis

Answer 14

done by heating an ester with an alkali
the ester is broken up into an alcohol and a salt