Question

An unknown compound, known to contain three carbon atoms, yields the following results. Classify the alcohol:

1. DNPH test: negative
    Dichromate test: negative
    Iodoform test: negative

3

Answer 1

The unknown alcohol compound has three carbon atoms-

Now we will briefly discuss about alcohol and there tests

a) DNHP test- (2,4 dinitro phenyl hydrazine test):

DNPH test is generally carried out for aldehyde or ketone functional group. Only Aldehyde or ketone gave (orange or red, yellow precipitate) positive test alcohols does show this test

b) Dichromate test-

This test is used for distinguish between primary and secondary alcohol.

Primary alcohol oxidize to give acid.

Secondary alcohol oxidize to ketone

Only primary and secondary alcohol shows positive test.

Tertiary alcohol does not show this test

c) Iodoform test:

This test is specific for only those alcohol having methyl (-CH3) and hydrogen (H) attached to carbon e.g. Ethanol and butanol.

Primary and secondary alcohol oxidize to aldehyde or ketone.

Tertiary alcohol shows negative test

According to above alcohol test the unknown compound is primary alcohol which is showing positive dichromate test.

The possible structure of the primary alcohol is as follows