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(CHEM111)[2001](s)quiz3~1463^_10037.pdf
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Quiz #3, CHEM 111, Fall Semester, 2001/2002
Student Name: Student ID #: Section:

Note: You are required to complete all questions independently. Reference materials and textbook are prohibited. Total marks for this quiz are 50 points.
Question 1: Draw the line-bond (Kekul) structures of the following molecules. (5 points)
(A) (4Z)-2,4-Dimethyl-1,4-hexadiene (B) trans-3-Hexene
Answer:

(A) (B)
Question 2: Among the alkenes given below, which compound is the most stable? Using molecular orbital theory for your reasoning. (10 points)

H3C
CH3H3C
H3C H3C

CH3H3C
CH3 H
3C H
3C
CH3
(C) (D) (E) (F)
Answer:
Question 3: When (G) is treated with strong acid at room temperature, isomerization occurs by the following mechanism to give (H). At equilibrium, the product mixture contains about 30% (G) and about 70% (H). Calculate Keq for the reaction. Which alkene is more stable? Why? (10 points)
H
H

H
H
CH3
CH3

H CH3 H+

H

H +H+
CH3
CH3
CH3
(G) (ca. 30%) (H) (ca. 70%)
Answer:
1

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Question 4: Rearrangement of (I) to (J) occurs as shown below. Provide your reasoning for the driving force which makes the rearrangement possible. In the provided box below, sketch a reaction energy diagram and label the parts corresponding to (I), (J), and transition state. Using the Hammond postulate to estimate the position of the transition state (close to I or J) (10 points).
CH3

CH3 H3C C CH2

H3C
C CH2CH3 CH3
(I)(J)
Answer (complete the energy diagram in the box provided below):
(write your reasoning here)

Question 5: Sketch a reaction energy diagram for a two-step reaction with an endergonic first step and an exergonic second step. The first step is the rate-determining step and the product is more stable than the reactant. Label the parts of the diagram corresponding to reactant, product, intermediate, activation energies for the first and second steps, and the free energy change of the allover reaction. (15 points)
Answer (complete the energy diagram in the box provided below):

Reaction progress
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