Question

a) i) Identify 'A' and 'B'. CH3-CH=CH2 in the presence of H20 gives A. A on reacting with CrO3 gives B.​

Answer 1

SOLUTION:

CH3-CH=CH2 is an alkene with double bond. All alkene, in presence of water, gives alcohol. This is called hydration of alkenes

CH3CH=CH2 + H2O --(H+)--> CH3CH2CHOH

mechanism:

step 1:

addition of H+ electrophile to pi bond.

step 2:

addition of H2O nucleophile to cation.

CrO3 is a strong oxidizing agent

All primary alcohol on oxidation give aldehyde

CH3CH2CHOH($1^{\circ}$ carbon) + CrO3 ----------> CH3CH2CH=O(aldehyde)+H20

CH3CHOHCH3($2^{\circ}$ carbon}+CrO3------------->CH3COCH3(acetone)+H20

       

So compound A is propanol CH3CH2CHOH

And compound B is propan-al or acetone CH3COCH3