Organic Chemistry 32-235
Practice Questions for Exam #2
Part 1: (Circle only
ONE
choice, circling more than one will be counted as wrong!)
4 points each
1. The correct IUPAC name for the following compound is:
(A) (1R, 3R)-1-chloro-3-methylcyclohexane
(B) (1R, 3S)-1-chloro-3-methylcyclohexane
(C) (1S, 3S)-1-chloro-3-methylcyclohexane
(D) (1S, 3R)-1-chloro-3-methylcyclohexane
(E)
None of the above.
The Key here is to determine the configuration R or S for each chiral carbon. The answer here is 1S,
2S.
2.
Consider the S
N
1 reaction of tert-butyl chloride with iodide ion:
(CH
3
)
3
C Cl
+ I
(CH
3
)
3
C I
Cl
+
If the concentration of iodide ion is doubled, the rate of forming tert-butyl iodide will:
(hint: consider mechanism, i.e. how is the product formed?)
(A) Double.
(B) Increase 4 times.
(C) Remain the same.
(D) Decrease.
(E) None of the above.
In SN1 reaction, the rate is independent of the nucleophile involved since the nucleophile is not
involved in the rate determining step. Thus the anwer is C.
3.
The relationship between the following two structures is:
(A) enantiomers
(B) diastereomers
(C) structural isomers
(D) identical
(E) none of the above
The key here is to know the definition of all terms and then determine R or S configuration for each
chiral carbon. The answer is (B) (by definition)
4.
The specific rotation of pure (R)-2-butanol is -13.5
°
. What % of a mixture of the two
enantiomeric forms is (S)-2-butanol if the specific rotation of this mixture is
-5
.4
°
?
(A) 40%
(B) 30%
(C) 60%
(D) 70%
(E) None of the above
The answer is B since e.e. is 40% favoring R. (5.4/13.5=40%)
CH
3
H
Cl
H
CH
3
H
OH
OH
H
CH
3
CH
3
HO
H
OH
H
CH
3
