The stereospecificity of the reactions is a very good evidence that E2 reactions proceed through an anti-periplanar transition state. More evidence comes from the reactions of substituted cyclohexanes. Generally, all cyclohexanes are most stable in chair conformations. we know that substituets on cyclohexanes can be parallel with one another only if they are both axial. an equatorial C-X bond is anti-periplanar only to C-C bonds and cannot take part in an elimination. for unsubstitueted cyclohexyl halides treated with base, this is not a problem because, although the axial conformer is less stable, there is still a significant amount present and elimination can take place from thi conformer

Q. What is correct during dehydrobromiation of trans-2-methyl bromocyclohexane via `E_(2)` mechanism.

Options

A. Only 3-Mthylcyclohexene is formed
B. 3-methylcyclohexene is obtained as major while 1-methylcyclohexene are formed
C. Equal amounts of 3-methylcyclohexene and 1-methylcyclohexene are formed
D. Only 1-methylclohexene is formed.

Answer

A