Explain the stereochemistry of the products from `E2` dehalogenation with `I^(Θ)` of the following.
`a.` `(i)` Meso `-2-3-`dibromobutane and `(ii)` `S,S-2,3-` dibromo`-` butane.
`b.` `E2-` dehydrobromination of `(i)` `R,R-2,3-` dibromobutane and `(ii)` meso`-(R,S)-2,3-` debromobutane
`c.` From which conformation of bromocyclohexane in the `E2` dehydrobromination is best achieved.

Explanation

a. i.
ii.
b. i.

`ii.`
c. The most conformation is `Br` in equatorial position.
But it cannot assume an anti `-` coplanar position with vicinal `H` atom (it should be trans diaxial).
Therefore, anti `-` coplanarity can be achieved with `Br` (axial) with vicinal `H` atome (trans diaxial).