Which of the following quaternary ammonium hydroxides undergoes Saytzeff s elimination ?
`A[CH_(3)CH_(2)underset(Me)underset(|)overset(Me)overset(|)NCH_(2)CH_(2)CH_(3)]^(+)Ohbar`
` B[CH_(3)CH_(2)CH_(2)underset(CH_(3))underset(|)(CHNMe_(3))]^(+)OHbar`
`C[PhCH_(2)CH_(2)underset(Me)underset(|)overset(Me)overset(|)NCHMe_(3)]^(+)OHbar`
`D[CH_(3)CH_(2)-underset(Me)underset(|)overset(Me)overset(|)N-C(CH_(3))_(2)]^(+)OHbar` .

Options

A. A,B
B. C,D
C. B,C
D. A,D

Answer

B

Explanation

In `C` the saytzeff product `PhCH = CH_(2)` and not the Hofmann product `H_(2)C =CH_(2)` is formed The greatly increased acidity of the benzylic `betaH` and the stability of the conjugated alkene influence the course of the reaction Thermal decomposition of `(D)` yield `(CH_(3))_(2)C=CH_(2+)+ EtNMe_(2) (93%)` and `CH_(2)=CH_(2)+t-BuNMe_(2)(7%)` This result is Saytzeff not Hofmann product There are two types of primary `(1^(@)) beta` hydrogen atoms one on `CH_(3)CH_(2)` and the t-Bu group is favoured statistically (nine from `C(CH_(3))_(3)` vs three from `CH_(3)CH_(2)`) and also because a more stable alkene is formed .