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(chem111)[2010](f)midterm~3840^_10032.pdf
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CHEM 111 Organic Chemistry I
Difficulty Level: 1.15 MID-TERM EXAMINATION
Your marks are (Fall Semester, 19 October 2002)
normalized by a

Instructor: Dr. Wei-Min Dai
factor of 1.15 in the
grade calculation.

Problems Set
Note: This is a close-book examination. You are required to work on ALL problems independently. The maximum time for answering this problems set is 80 minutes. You can work on the problems in any order you like. Start with the easy problems first and do the hard ones later. Use the Examination Booklet to present your answers. Do not forget to write down your name, student ID number, course title, and date on your Examination Booklet.
Total marks are 350 points.
1. Multiple choice problems. Pick up only ONE answer and write it down on the answering booklet. (8 points each)
(1a) The boron atom in [BF4] is:
A. sp hybridization
B. sp2 hybridization
C. sp3 hybridization
D. trigonal
(1b) Consider the resonance structures, how many negative charge is on each oxygen of the CO32?
A. one third B. two thirds
C. one D. two
(1c) Predict the order of pKa value of the following substances aCd.
O OOO
H3CCOH FCH2COH F2CHCOH F3CCOH
abc d
A. a > b > c > d B. a < b < c < d
C. b > c > d > a D. b < c < d < a
(1d) Which is the most stable conformation of 3-methylhexane?

CH3
CH3

CH3
HCH3 H CH2CH3
H B. CH3CH2
A. H D.
H C.
CH2CH3 CH3CH2 H
H
CH3CH2 H CH3CH2 CH3CH2 H
HH
CH2CH3 H
(1e) For the formula of C7H10F3NS, the degree of unsaturation is:
A. one B. two
C. three D. four
(1f) Reaction of NBS with cyclopentene in H2OCDMSO forms a bromohydrin whose stereochemistry is:
A. anti B. syn
C. trans D. cis
(1g) The axial conformation of fluorocyclohexane is 1.0 kJ/mol less stable than the equatorial conformation. What is the energy cost of a 1,3-diaxial interaction between hydrogen and fluorine?
A. 2.0 kJ/mol F
B. 1.0 kJ/mol
C. 0.5 kJ/mol
D. 0.25 kJ/mol
(1h) The strain of a 1,3-diaxial interaction between hydrogen and hydroxy group (OH) in cyclohexanol is 2.1 kJ/mol. Estimate the energy difference between the gauch and anti conformations of 1-propanol.
A. 4.2 kJ/mol
H OH
H CH3 CH2 CH2 OH
B. 2.1 kJ/mol H
C. 1.05 kJ/mol
H
D. 0.7 kJ/mol H H H 1-propanol
cyclohexanol
2. For each of the following compounds, use "H" and "L" to mark the high and low priority of the four groups attached on the double bond and assign E or Z geometry. (5 points each)
(2a) (2b)

CH2I Cl
CC



CH2SCH3HN

CHO
CC
NH2
(2c) (2d)
F
CH3 CH3CH2 HC
CH2 CC

CC

CH3 CH2OH
H3C
H


3. Draw the most stable conformation for the following molecules. (7 points each)
(3a) (3b) (3c)

CH3
F

C(CH3)3
Cl


I (H3C)2N




4. Alkene C undergoes an electrophilic addition with HCl to form D. Using the curved-arrow notation, propose a mechanism to account for the result. (35 points)
H3C

H3C
HCl Cl

eth