Question

An alcohol of unknown structure gave a positive Lucas test in about five minutes. When alcohol was heated with concentrated `H_(2)SO_(4)` an alkene was formed with the formula `C_(4)H_(8)`. Ozonolysis of this alkene gave a single product, `C_(2)H_(4)O`. What was the structure of the alcohol ?

Answer 1

The ozonolysis product of alkene `C_(4)H_(8)` is `C_(2)H_(4)O` i.e. ethanal `(CH_(3)CH=O)`. Since tow molecules of ethanal have been dormed therefore, alkene is but-2-ene `(CH_(3)CH=CH-CH_(3))`.

The alkene has beeen formed by the dehydraction of alcohol with concentratrated sulphuric acid. Since the alcohol gives a positive Lucas test within five minutes, it is expected to be a secondary alcohol. It is therefore, butan-2-ol `(CH_(3)CHOHCH_(2)CH_(3))`
`underset("Butan-2-ol")(CH_(3)-overset(OH)overset(|)(CH)-CH_(2)-CH_(3)) underset("Heat")overset(H_(2)SO_(4) (conc.))(rarr) underset("But-2-ene")(CH_(3)-CH=CH-CH_(3))`