Spring 2002 Org II Exam #2
Ch 18-19
(100 points)
NAME:
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1)
Name the general class of organic compound that each of these
molecules belong to, and circle the molecule that is also known as a
Schiff base. (11pts)
O
R C NH2
R N3
2)
O
R C OH
H2C CH2
O
O
C
R
R
O
R C R
HO
R
C
OH
R
O
R C H
R
N
R C R
R NH2
R C N
Circle the stronger base in the following pairs, and in a sentence
explain your choice. (6pts)
H
N
(a)
N
(b)
NH3
CH3CH2NH2
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3) Draw the Lewis structure (including lone pairs) for the following
molecules. (12pts)
R NO2
R CN
R NCO
PPh3
4) Name the following compounds in IUPAC acceptable terms. (15pts)
H3C
O
C
H
H3C
HN
C
O
O
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5) Aniline (Ph-NH2) reacts with nitrous acid (HONO) to form a diazonium
salt.
Draw a Lewis structure (with lone pairs) for nitrous acid. (2pts)
During the reaction, Nitrous acid undergoes acid catalyzed dehydration to
produce the nitrosonium cation (NO+). Draw the mechanism for this
transformation, and show that the nitrosonium cation is resonance
stabilized. (8pts)
HONO
H+
H2O
N O+
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6) What is the definition of a condensation reaction? (2pts)
Provide a chemical reaction that is an example of a condensation
reaction. (2pts)
What is the definition of a protecting group? (2pts)
Provide an example of a protecting group and the group it protects. (3pts)
Draw a synthetic scheme that requires and exemplifies the use of a
protecting group. (6pts)
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7) Give the products formed in five of the following reactions. (15pts)
O
1)Ph3P, CH3-Br
(a)
2) BuLi
3) warm
O
(b)
(c)
(d)
1) PhMgBr
H C H
2) H3O+
O
H C H
Ph NH2
Ph NH2
H+
1) NaNO2, HCl
2) CuBr, HBr, heat
NH
(e)
Ph
1) excess CH3-Br
2) Ag2O, H2O, heat
(f)
H3C NH2
O
excess F3C C Cl
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8) Explain why aldehydes and ketones undergo nucleophilic addition, but
acid chlorides undergo nucleophilic acyl substitution. (9pts)
Nucleophilic Addition
O
R C R
CH3OH
O H
R C OCH3
R
O
Nucleophilic Acyl
Substitution
CH3OH
R C Cl
O
R C OCH3
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9) Explain why a ketone must have three or more carbon atoms. (7pts)
*Bonus question* (up to 4pts)
For the reaction of a primary amine with a ketone, the optimum pH for imine
formation is around 4.5. Explain why this reaction goes more slowly both at
lower and higher pH.
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