Find the reactants which on heating with alcoholic KOH produces the compound
`CH_(3)-CH_(2)-CH_(2)-CH=CH_(2)`

Options

A. `CH_(3)-underset(Br)underset(|)CH-CH_(2)-CH_(2)-CH_(3)`
B. `CH_(3)-CH_(2)-underset(Br)underset(|)CH-CH_(2)-CH_(3)`
C. `CH_(3)-CH_(2)-CH_(2)-underset(Br)underset(|)CH-CH_(2)Br`
D. `CH_(3)-CH_(2)-CH_(2)-CH_(2)-underset(Br)underset(|)CH_(2)`

Answer

B

Explanation

On heating haloalkane with alcoholic KOH
gives ` CH_(3) - CH_(2) - CH_(2) - CH = CH_(2)` are :
(i) (i)` CH_(3) - underset(Br) underset(|)CH- CH_(2) - CH-CH_(3)`
` underset("Elimination") overset (KOH(alc)) (to) CH_(2) = CH - CH_(2) - CH_(2) - CH_(3)`
[by using Hofmann's rule ] .
Hence , the formation of given product is possible .
(ii) `CH_(3) - CH_(2) - underset(Br)underset(|)(C)H- CH_(2) - CH_(3)`
` overset ("KOH(alc)")(to) CH_(3) - CH = CH - CH_(2) - CH_(3)`
Hence , the fomation of given product is not possible .
(iii) ` CH_(3) - CH_(2)-CH_(2) - underset(Br) underset (|)CH- CH_(2)Br `
` underset("Elimination") overset ("KOH (alc.)") (to) CH_(3)-CH_(2) - CH_(2) -CH = CHBr ` .
Hence, the formation of given product is not possible .
(iv) ` CH_(3) - CH_(2) - CH_(2) - CH_(2) - underset (Br) underset(|)(C)H_(2)`
` underset ("Elimination") overset ("KOH(alc)")(to) CH_(3) - CH_(2) - CH_(2) - CH = CH_(2)`
Hence , the formation of given product is possible. Thus (i) and (iv) are the reactants that can give that given product.
Hence, option (b) is the correct answer .