Name: Isomerism in Alcohols
Uploaded: 2019-07-19
Duration: 5 min 5 s
Description: Chemical compounds that have the same chemical formulae but differ in property and arrangement of atoms in the molecule are called an isomer. Dive into this...

Question

What happens when primary, secondary and tertiary alcohols are

i) oxidised with $K_{2} {Cr}_{2} O_{7}$ and $H_{2} {SO}_{4}$ ?

ii) passed over heated copper?

Accepted Answer

i) Reactions of primary, secondary and tertiary alcohol with $K_{2} {Cr}_{2} O_{7}$ and $H_{2} {SO}_{4}$ :

A primary alcohol is first oxidised to corresponding aldehyde when treated with acidified potassium dichromate. The aldehyde further readily gets oxidised to carboxylic acid.

${CH}_{3} - {CH}_{2} - OH + [O] \to_{dil . H_{2} {SO}_{4}}^{K_{2} {Cr}_{2} O_{7}} {CH}_{3} - CHO \to_{dil . H_{2} {SO}_{4}}^{K_{2} {Cr}_{2} O_{7}} {CH}_{3} - COOH$

A secondary alcohol is first oxidised to corresponding ketone when treated with acidified potassium dichromate. The ketone further readily gets oxidised to lower carboxylic acid, as ketone does not have $α -$ carbon.

Tertiary alcohol does contain $α -$ hydrogen. Hence, it does not get oxidised.

Reactions of primary, secondary and tertiary alcohol with hot copper:

When primary alcohol is passed over heated copper catalyst at $300 ° C$ , alcohol is dehydrogenated to form corresponding aldehyde.

${CH}_{3} - {CH}_{2} - OH \to_{300 ° C}^{Cu} {CH}_{3} - CHO + H_{2} ↑$

When secondary alcohol is passed over heated copper catalyst at $300 ° C$ , the alcohol is dehydrogenated to give ketone.

When tertiary alcohol is passed over heated copper catalyst at $300 ° C$ , it does not get dehydrogenated. It rather gets dehydrated to form alkene.

What happens when primary, secondary and tertiary alcohols are

i) oxidised with $K_{2} {Cr}_{2} O_{7}$ and $H_{2} {SO}_{4}$ ?

ii) passed over heated copper?

Important Questions on Alcohols

Learn and Prepare for any exam you want !

What happens when primary, secondary and tertiary alcohols are i) oxidised with K2Cr2O7 and H2SO4? ii) passed over heated copper?

Important Questions on Alcohols

Learn and Prepare for any exam you want !

What happens when primary, secondary and tertiary alcohols are

i) oxidised with $K_{2} {Cr}_{2} O_{7}$ and $H_{2} {SO}_{4}$ ?

ii) passed over heated copper?