The number of no bond resonance structures possible for but-1-ene and a `3^(@)` carbocation having methyl, ethyl and isobutyl groups on cationic carbon respectively are

Options

A. `3,7`
B. `4,6`
C. `2,7`
D. `5,6`

Answer

C

Explanation

No bond resonance implies hyper conjuction. It depends on number of `alpha -H`
For But-1-ene,
`CH_(3) -CH_(2) -CH =CH_(2)`
Number of `alpha -H =2`
`therefore` Number of NO bond resonance =2
For `3^(@)` carbocation,
`{:(" "CH_(3)), (" "|) ,(CH_(3) - CH_(2)-C^(o+)),(" "|), (CH_(2) - CH- CH_(2)),( " "|) ,(" "CH_(3)):}`
Number of `alpha -H =7`
`therefore` Number of no bond resonacne = 7