Question

Alcohol gives Lucas a test in about 5 minutes. When the alcohol was treated with hot concentrated \[{H_2}S{O_4}\], it gave an alkene of molecular formula \[{C_4}{H_8}\] which on ozonolysis gives single product with molecular formula \[{C_2}{H_4}O\]. The structure of alcohol is:
(A) \[C{H_3}CH(OH)C{H_2}C{H_2}C{H_3}\]
(B) \[C{H_3}C{H_2}C{H_2}C{H_2}OH\]
(C) \[C{H_3}CH(OH)C{H_2}C{H_3}\]
(D) \[{\left( {C{H_3}} \right)_3}C(OH)\]

Answer 1

Hint: Try to recall that is used to distinguish between primary, secondary and tertiary alcohols by treating alcohol with concentrated hydrochloric acid. Now, by using this you can easily find the correct option from the given ones.

Complete step by step solution:
It is known to you that in Lucas test, alcohol is treated with an equimolar mixture of concentrated hydrochloric acid and anhydrous zinc chloride (called Lucas reagent).
In Lucas tests/reactions, the alcohols get converted into alkyl halides.
Since the alkyl halides are insoluble in water their formation is indicated by the appearance of turbidity in the reaction mixture.
Since the order of reactivity of alcohols with halogen acids is tertiary>secondary>primary, the time required for the appearance of cloudiness will be different in different alcohols.
If turbidity appears immediately, the alcohol is tertiary, if the turbidity appears within five minutes, the alcohol is secondary and if turbidity appears only upon heating, the alcohol may be primary.
Now, coming to the question, since alcohol gives Lucas test in 5 minutes so it must be secondary alcohol and the alcohol gives alkene \[{C_4}{H_8}\] on dehydration so it must contain 4 carbon atoms.

Therefore, from above we can conclude that option C is the correct option to the given question.

Note:
It should be remembered that victor meyer test is also used to find out if the given alcohol is primary, secondary and tertiary. Formation of a blood red colour indicates the primary alcohol, formation of a blue colour shows the original alcohol to be secondary while, a colourless solution means that the alcohol is a tertiary alcohol.