Diphenylacetylene can be synthesized by the double dehydrohalogenation of 1,2- dibromo-l,2...

Diphenylacetylene can be synthesized by the double dehydrohalogenation of 1,2- dibromo-l,2-diphenylethene. The sequence starting from (E)-1,2-diphenylethene (stilbene) consists of bromination to give the dibromide, followed by dehydrohalogenation to give a vinylic bromide, then a second dehydrohalogenation to give diphenylacetylene.

(a) What is the structure, including stereochemistry, of the vinylic bromide?

(b) If the sequence starts with (Z)-l,2-dibromo-1.2-diphenylethene. what is (are) the structure(s) of the intermediate dibromide(s)? What is the structure of the vinylic bromide?