2010 che 230 exam 3 solutions - Department of Chemistry - Illinois ...

1. Which of the following cycloalkanes is the most stable (20 pts)
(a)
(b)
(c)
(d)
cyclopropane
cyclobutane
cyclohexane
cyclodecane
C
2. Which definition presented here is best for enantiomers (20 pts)
(a)
(b)
(c)
(d)
The exact opposite of diastereomers
Stereoisomers that cannot be related by a mirror plane
Non-superimposable mirror image molecules
Molecules that are not superimposable and have optical activity
C
3. Which definition presented here is best for diastereomers (20 pts)
(a)
(b)
(c)
(d)
The exact opposite of enantiomers
Stereoisomers that cannot be related by a mirror plane
Non-superimposable mirror image molecules
Molecules that are not superimposable and have optical activity
B
4. Which is a true statement concerning the transition state of an S N 2 reaction (20 pts)
(a)
(b)
(c)
(d)
Involves only the electrophile
Involves only the nucleophile
Involves both the nucleophile and electrophile
Involves both the nucleophile and electrophile and the reaction solvent
C
5. What is the rate expression used for the S N 1 reaction. (20 pts)
(a)
(b)
(c)
(d)
Rate = k[nucleophile]
Rate = k[electrophile]
Rate = k[nucleophile][electrophile]
Rate = k[nucleophile][nucleophile]
B
6. When a chiral substrate undergoes S N 1 reaction at the asymmetric carbon, the final product has (20 pts)
(a)
(b)
(c)
(d)
retention of stereochemical configuration
stereochemical scrambling
a change from (S) to (R) stereochemistry
inversion of stereochemical configuration
B
7. Increasing the concentration of an electrophile in a typical S N 1 reaction by a factor of 3 and the
concentration of the nucleophile by a factor of 3 will change the reaction rate: (20 pts)
(a) increase by a factor of 3
(b) increase by a factor of 6
(c) increase by a factor of 9
(d) increase by a factor of 12
A
© 2010 Prof. S. R. Hitchcock, Department of Chemistry, Illinois State University, Normal, IL 61790-4160 1