Homework Graded Problem #16 Answer Key
Deadline: 3:00 p.m., Thursday, 4/10/08 LATE WORK WILL NOT BE ACCEPTED OR GRADED!!!
This problem is worth a total of 20 raw points. When 1,3-butadiene is treated with Cl2 in CH3OH solvent, a mixture of isomeric products is isolated. The overall transformation and the relative amount of each constitutional isomer formed as a result of the reaction are shown below:
+
CH3OH Cl Cl
Cl
OCH3
+
OCH3 Cl (70%; racemic)
(30%; mixture of E and Z)
(a) (4 points) Does this reaction take place under kinetic control or thermodynamic control. your Circle response below. It is not necessary to provide an explanation.
KINETIC CONTROL
THERMODYNAMIC CONTROL
(b) (16 points) Propose a mechanism which accounts for formation of both products. Use curved arrows to show movement of electron pairs, and draw structures of all important reaction intermediates. If an intermediate is a resonance hybrid, please draw all of the important contributing resonance structures!!!
Cl Cl Cl Cl Cl
(resonance-stabilized allylic carbocation)
CH3OH
CH3OH
OCH3 Cl
CH3OH Cl
H O
CH3 Cl O H CH3
CH3OH2 CH3OH
Cl OCH3 CH3OH2