CHEM 321
Organic Chemistry I
Exam 1
10/12/12
Print Name:
1 point
Part I. Short Answer – (59 total number points) Answer all parts for the following questions.
1) (5 points) For the compound below, answer the following questions:
a) Put a circle on the atoms, which are sp2-hybridized.
b) Put a triangle around the atoms, which are sp-hybridized.
c) The remaining atoms are:
O
O
N
N
2) (3 points) For the compound above, there are examples of triple bonds, double bonds, and single
bonds. Using those bonds, put them in decreasing bond lengths (e.g., C-C > C-X).
3) (3 points) Draw both chair forms of the structure(s) below. Indicate the more stable chair form
for each case.
CH3
CH(CH3)2
Cl
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4) (11 points) Provide in the most appropriate answer by writing the complete answer for the
following statements using the choice below. You may use a word more than once:
Identical
Conformational Enantiomers
Enantiomers
Conformational Diastereomers
Diastereomers
Relationship between the mirror image of methylcyclohexane
Relationship between the chair interconversion of methylcyclohexane
Relationship between the mirror image of trans1,4-dimethylcyclohexane
Relationship between the chair interconversion of cis-1,3-dibromocyclohexane
Relationship between the chair interconversion of trans-1,2-dimethylcyclohexane
Relationship between the mirror image of 1,1-dichlorocyclohexane
Relationship between the chair interconversion of trans-1,3-diethylcyclohexane
Relationship between the mirror image of cis-1-isopropyl-3-methylcyclohexane
Relationship between the chair interconversion of cis-1,4-diethylcyclohexane
Relationship between the mirror image of cis-1,4-dimethylcyclohexane
Relationship between the chair interconversion of cis-1-bromo-3methylcyclohexane
2
5) (4 points total) Circle the entire molecule if it can exist as cis/trans (E/Z) isomers? Put a
square around the entire molecule, if it is overall chiral. If there is a stereogenic carbon, put a
star on it.
(a) (CH3) 2C=CHCH2CH2CH(CH3)CH2CH2OH
(b) (CH3)HC=C=CHCH2C(CH3)=CHCH2OH
6) (3 points each/total 9 points) Name the following compounds:
OH
7) (1 point each/16 total points) For each statement, write the complete word of True/False
for each statement below.
a)
Pentahelicene is a chiral compound.
b)
2,3-Hexadiene is an achiral compound.
c)
3,4,5-octatriene is an achiral compound.
d)
All biphenyl compounds are achiral.
e)
There are 4 stereoisomers for 3,5-dibromoheptane.
f)
There is the same number of stereoisomers when there is no free
rotation about the carbon-carbon single bonds for 2,3-dibromo-2chloro-3-fluorobutane.
g)
Cis-1,2-dimethylcyclohexane is an example of a meso stereoisomer
and is overall chiral.
h)
A chair flip changes both the position of the group from equatorial
to axial as well as the chirality of that center.
i)
The torsional and angle strain in planar cyclopentane is higher as
compared to planar cyclohexane.
j)
The angle strain is lower than the interorbital strain in
cyclopropane.
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k)
The heat of formation in the standard states of cycloheptane is less
than that of cyclobutane.
l)
For cis-1,2-dibromocyclohexane, there is always two gauche
interactions for each chair conformation.
m)
For diastereomers, they have different physical properties with
the exception optical rotation.
n)
The ring flip of the diequatorial form to the diaxial form will
racemize optically active trans-1,3-dimethylcyclohexane.
o)
The highest transition state for the chair conformational flip it the
half chair at a cost of 12 kcal/mol.
p)
An alcohol may be both a Bronsted acid and base.
4
8) (8 points) Morphine has the structure below. Star all of the chiral (stereogenic centers) in
morphine. Then, assign chirality (R or S) to each of those centers. Theoretically, how many possible
stereoisomers would there be for the structure below?
HO
O
N
H
CH3
HO
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Part II. Reaction and Mechanisms. (20 points) For reaction a, show all of the products (7 points).
Note the stereochemistry (R/S and * the chiral centers) and major/minor product(s) where
necessary. Also, provide the mechanism for the formation of the products for reaction a (7 points).
H2OCH2CH3
a)
HOCH2CH3
H-Br
b)
A
Mg
ether
B
D-OD
C
Provide Structures for (start chiral centers; 2 points each):
A:
B:
C:
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Part III Short Answer Essay (21 points).
9) (7 points) Draw all of the possible stereoisomers of 4,5-dibromo-3,3,7,7tetrachlorooctane. State the relationships between isomers and label R/S if applicable.
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10) (14 points) Draw all of the possible chair forms and stereoisomers of cis- and trans-1propyl-3-isopropylcyclohexane. State the relationships between isomers, state the
relationships between their flipped isomers, label R/S if applicable, and specify their
stability.
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