(1) The isomerization of dimethyl maleate to dimethyl fumarate, catalyzed by bromine, follows what type of reaction mechanism?

(a) catalytic hydrogenation

(b) nucleophilic substitution

(c) Diels-Alder

(d) free-radical

(2) What is the purpose of the an incandescent light (a light bulb) during the procedure in this isomerization reaction?

(a) the incandescent light is used to visualize the TLC plates

(b) so that you can watch the reaction closely

(c) the bromine molecule undergoes photochemical dissociation in the presence of light, thus forming two bromine atoms which initiate the free radical bromination reaction

(3) Bromine is orange in color when it is in the form Br₂. Thus, you will know that the reaction is complete by the observation of a colorless solution.

(a) true

(b) false

(4) Dimethyl fumarate is less polar than dimethyl maleate, because the fumarate does not have a net dipole moment. You would expect the fumarate to be more soluble than the maleate in a non-polar solvent like hexanes. However, it is NOT soluble in hexanes, and precipitates out of solution, while the maleate remains in solution. Why?

(a) the melting point of dimethyl fumarate is less than the boiling point of the hexanes

(b) dimethyl maleate is very soluble in the non-polar hexanes because it dimerizes

(c) the trans configuration of the dimethyl fumarate enable it to pack into a crystal lattice structure, thus crystallizing out of the solution

Answers.