EXAM 4 REVIEW QUESTIONS
Chem 227 - Fall 1997
©Kenn Harding, 1997
1. Draw the structure corresponding to the IUPAC names below.
a) p-nitrotoluene
2. For each molecule below predict whether it would be expected to
show aromatic character or not (YES or NO) and explain your answer in each
case.
4. Predict the major products for the following reactions. If more than
one product is expected in significant amounts, draw all of them. Show
stereochemistry for all reactions marked with an asterisk (*).
f)
h)
j)
k)
m)
o)
p)
5. Give the reagent(s) necessary for carrying out the transformation
shown below. Write the answer over the arrows.
a)
b) More than one step
6. Give an example of a substituted benzene which is unreactive in
Friedel-Crafts alkylation reactions.
8. Write a complete stepwise mechanism for the following reactions.
Show all intermediate structures and show all electron flow using the curved
arrow convention. Show stereochemistry clearly at all steps.
a)
9. Give the reagents to complete the following reactions. More than
one set of reagents may be required.
a)
10. Which of the following is not a limitation of Friedel-Crafts
alkylation reactions?
A. Polyalkylation of the ring occurs.
B. Rearrangements of the alkyl group often occur.
C. Carbocations can only be generated from alkyl halides.
D. Deactivated rings do not undergo Friedel-Crafts reactions.
11. Circle all compounds below which are predicted to be aromatic
and draw a big X through those that are not aromatic.
3. List three differences between reactions that proceed by SN2 and reactions that proceed by SN1 mechanisms
i)
ii)
iii)
4. Predict the major products for the following reactions. If more than one product is expected in significant amounts, draw all of them.
a)
b)
g)
h)
l)
6. Give 2 examples of polar aprotic solvents that facilitate SN2
reactions.
a)
b)
7. Consider the reactions below in answering the following questions
a) Which reaction(s) will give chiral products?
b) Which reaction(s) will give optically active products?
c) Which reaction involves the stronger nucleophile?
d) Which reaction is expected to proceed by an two-step mechanism?
11. Circle the correct answer
a) What is the order increasing reactivity for the following nucleophiles?
(least nucleophilic first)
CH3OH; H2O; OH-; CH3O-
I II III IV
i) I, IV, II, III
ii) IV, II, I, II
iii) II, I, III, IV
iv) IV, III, I, II
b) What is the order of increasing reactivity for the following halides
in an SN2 reaction with KI in acetone?
(least reactive first)
i)I, IV, III, II
ii) IV, I, III, II
iii) II, IIII, I, IV
iv) III, II, IV, I
c) Which of the following statements apply to an SN1
reaction?
I) The reaction is first order in alkyl halide an dfirst order in the nucleophile.
II) The order of reactivity is methyl > 1o > 2o > 3o
III) The reaction is first order in alkyl halide and zero order in the nucleophile
IV) Rearrangements are common
a) I, II
b) III, IV
c) I, IV
d) II, IV
d) Which of the following statements apply to an SN2
reaction?
I) The reaction is first order in alkyl halide and first order in the nucleophile
II) The order of reactivity is methyl > 1o > 2o > 3o
III) The reaction is first order in alkyl halide and zero order in the nucleophile
IV) Rearrangements are common
7. For each of the following pairs of reactions, circle the letter
of the reaction that is expected to be faster. Indicate the reaction mechanism
expected to be followed in each case and explain the reason(s) for the
reactivity order you selected.
a)
b)
8. Write a complete stepwise mechanism for the following reactions.
Show all intermediate structures and show all electron flow using the curved
arrow convention. Show stereochemistry clearly at all steps.
1. (6 pts) Draw structures for the following compounds:
a) (Ignore this part - structure on left) b) p-bromoaniline
2. (9 pts) For each structure below, predict whether it would be expected to show aromatic character (YES or NO) and explain your answer.
3. (24 pts) Predict the major organic products for the following reactions.
If no single product is expected to predominate, draw all expected products.
a)
f)
5. (5 pts) List three groups which deactivate a benzene ring toward
electrophilic aromatic substitution and circle the group which is the weakest
deactivator.
See Table 16.1 Use a halogen as best example of weak deactivator.
6. (12 pts) Write a complete stepwise mechanism for the EAS reaction
of NO2+ with nitrobenzene. Show contributing resonance
structures for intermediate carbocation and show all electron flow using
the curved arrow convention. Show formation of the major product
only.
8. (8 pts) Select the best set of reagents and sequence of addition
to complete each of the following converstions. Place the letter of the
reagent of your choice in the blank for each reaction.
| A. 1. HNO3, H2SO4
2. CH3COCl, AlCl3 |
B. 1. Br2, FeBr3
2. HNO3, H2SO4 |
| C. 1. CH3NO2, AlCl3
2. Br2, FeBr3 |
D. 1. CH3COCl, AlCl3
2. H2SO4, HNO3 |
| E. 1. HNO3, H2SO4
2. Br2, FeBr3 |
F. 1. CH3CO3H, H2SO4
2. H2SO4, HNO3 |
| G. 1. Br2, FeBr3
2. Mg, Ether 3. CH3CO2CH3 4. HNO3, H2SO4 |
H. 1. HBr, peroxides
2. O2N-Cl |
a) E
Bromination first would lead to no selectivity in the nitration step
since every hydrogen in 1,2-dibromobenzene is ortho or para to a bromine.
b) D
Nitration first would fail because nitrobenzene is unreactive in Friedel-Crafts
reactions.
9. (4 pts) An attempt to synthesize compound I as shown below failed;
another compound was obtained instead. Write the structure of the compound
expected to result from this reaction.
