91Ó°ÊÓ

What stereochemistry do you expect for the trisubstituted alkene obtained by E2 elimination of the following alkyl halide on treatment with KOH? (Reddish brown = Br.)

Which isomer would you expect to undergo E2 elimination faster, trans-1-bromo-4-tert-butylcyclohexane or cis-1-bromo-4-tert-butylcyclohexane? Draw each molecule in its more stable chair conformation, and explain your answer.

Tell whether each of the following reactions is likely to be S_N1, S_N2, E1, E1cB or E2:

c)

d) Tell whether each of the following reactions is likely to be S_N1, S_N2, E1, E1cB or E2:

Write the product you would expect from reaction of each of the following alkyl halides with (1)Na^+-SCH₃and (2)Na^+-OH(green = Cl):

a)

From which alkyl bromide was the following alkyl acetate made S_N2 byreaction? Write the reaction, showing all stereochemistry.

Assign R or S configuration to the following molecule, write the product you would expect from S_N2reaction with NaCN, and assign R or S configuration to the product (green = Cl):

Draw the structure and assign Z or E stereochemistry to the product you expect from E2 reaction of the following molecule with NaOH (green = Cl):

We saw in Section 8-7 that bromohydrins are converted into epoxides when treated with base. Propose a mechanism, using curved arrows to show the electron flow.

Metabolism of S-adenosylhomocysteine (Section 11-6) involves the following sequence. Propose a mechanism for the second step.