Question

Give the reagents J, L, N and products K, M in the following reaction scheme. ГОН K N NH,OH H H L HCN OH M (5 marks)

Answer 1

Reagent J:

conversion of butanol to butanal.

The reagent can be either PCC or DMP can make a mild oxidation of the primary alcohol to the aldehyde level.

PCC = Pyridinium chloro chromate

DMP = Dess martin periodinane

Thus

CH3-CH2-CH2-CH2OH $\rightarrow$    CH3CH2CH2CHO

Butanol              PCC or DMP / - 2H    Butanal.

Reagent L:

Conversion of Butanal to 3-hexanol.

The reagent required is the gridnard reagent ethyl magnesium bromide CH3-CH2-MgBr.followed by hydrolysis

CH3CH2CH2CHO + CH3CH2MgBr $\rightarrow$ CH3CH2CH2CH (OMgBr)-CH2CH3

CH3CH2CH2CH (OMgBr)-CH2CH3 + H2O $\rightarrow$ CH3CH2CH2CH(OH)CH2CH3   + Mg (OH)Br

Reagent N:

Conversion of Butanal to Butane:

This can be achieved by wolf kishner reduction . The reagent is hydrazine /KOH that is NH2-NH2 / KOH.

This reduces aldehydes to alkanes.

Product M:

Reaction of HCN 'w'ith aldehyde produces cyanohydrin

Thus butanal form butylcyanohydrin.

CH3CH2CH2CHO + HCN $\rightarrow$ CH3-CH2-CH2-CH(OH)CN

Product K:

Aldehydes with hydroxylamine and HCl produces oxime

Thus butanal form butoxime.

CH3-CH2-CH2-CHO + NH2OH / H+ $\rightarrow$ CH3-CH2-CH2-CH=N-OH + H2O

Thus

Reagent L N PCC or DMP Grignard reagent CH3CH2MgBr Wof-Kishner reagent, hydrazine/KOH