Question

Show how you would accomplish each of the following multistep conversions. Include all reagents and condtitions and show all reaction products.

4. Al Use conditions to selectively make the Z-alkene

Answer 1

1,2-phenyl ethane reacts with NBS (N-bromo succinamide) to form 1-bromo-1,2-diphenyl ethane.

Ph-CH2-CH2-Ph + NBS ------> Ph -CH(Br)-CH2-Ph

1-phenyl-1,2-diphenyl ethane reacts with NaNH2 to form stilbene.

Ph-CH(Br)-CH2-Ph + NaNH2 -----> Ph-CH=CH-Ph

Stilbene reacts with Br2 to form 1,2-dibromo-1,2-diphenyl ethane.

Ph-CH=CH-Ph + Br2 ------> Ph-CH(Br)-CH(Br)-Ph

1,2-dibromo-1,2-diphenyl ethane reacts with excess of NaNH2 yo form 1,2-diphenylethyne.

Ph-CH(Br)-CH(Br)-Ph + 2 equiv. NaNH2 -----> Ph-C $\equiv$ C-Ph

Alkyne on reduction with H2- Lindlar's catalyst produces CIS alkenes selectively.

Ph-C $\equiv$ C-Ph + H2-Lindlar's catalyst ------> Ph-CH=CH-Ph (cis product)