1.

A hydrocarbon, C_(4)H_(8), neither decolourised bromine in carbontetrachloride nor reacted with hydrogen bromide. When heated to 200^(@)C with hydrogen in presence of nickel catalyst, a new hydrocarbon, C_(4)H_(10) was formed. What was the orginal hydrocarbon?

Answer»

Solution :`C_(4)H_(8)` can have the following isomers:
`underset("1-Butene")(CH_(3)CH_(2))CH=CH_(2)""underset("2-Butene")(CH_(3)CH=CHCH_(3))""{:(CH_(2)-CH_(2)),("||"),(CH_(2)-CH_(2)),("Cyclobutane"):}`
1-Butene and 2-butene are ruled out as these decolourise BROMINE in carbontetrachloride and ALSO react with hydrogen bromide.
The hydrocarbon is cyclobutane. Cyclo-butane on reduction with hydrogenin presece of NICKEL opens up the ring and forms n-butane.
`underset(CH_(2))underset(|)CH_(2)-underset(CH_(2))underset(|)CH_(2)+H_(2)underset(200^(@)C)overset(Ni)toCH_(3)CH_(2)CH_(2)CH_(3)`


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