Question

Postlab Assignment for Exp 42   “A Wittig Reaction of trans-cinnamaldehyde”

1. Which of the two possible products (E,Eor E,Z) from our experiment is more thermodynamically stable? Briefly explain.

2. Of the three 1,4-diphenyl-1,3-butadiene isomers (E,Eor E,Z orZ,Z) indicate the most suitable diene that can be used as a reactant in a Diels-Alder reaction. Briefly explain your choice.

3. What is the benefit of triturating the product in 60 % ethanol?

4. The ylide you made in this experiment is fairly stable (more stable than an ylide made from CH₃Cl). Using chemical structures account for the extra stability of your ylide.

5. Supply the organic product for the Wittig reaction below.

     

Answer 1

Given,* which of the two possible products (h, h, or h,z) * from our experiment is more thermodynamically * stable of the three 1-4, diphenyl -1, 3-butadiene * isomers (h, h or h, z or z, z) indicate the most * suitable diene that can be used as a reactants * a diels - Alder reaction. * The slide you made in this experiment is * is fairly stable (more stable than an * field made from CH_3cl). Using chemical * structures account for the extra stability. * The transition state of E-isomer has lower energy than z-isomer: thus the major products is (E, E) - 1, 4 - diphenyl -1, 3 - butadiene * In is isomer both phenyl groups are on the same side. so steric repulsions occurred between the two phenyl groups, this results increase in energy of is isomer Diels alder reaction is concerted reaction occurred via