Chemistry 11Oa-Organic Chemistry
SECOND EXAM
October 2, 2009
Name (print) __
-------'-\(_c_'1<--
_
Cosmo Kramer: Environmental Activist, Petroleum Engineer.
The only known steady job Kramer had throughout the entire series was
when he went back to work at a bagel shop after being on strike for a
number of years. He only worked there for one episode, leaving to go back
on strike. He had a variety of ways to get money to live, including
gambling, working in various theater projects, acting out illnesses at a
medical school, getting a spot on the show Murphy Brown, and pitching
ideas for inventions like his Coffee Table Book; a book about coffee tables,
and celebrities with their coffee tables, that featured a cup-holder on the
cover and legs on the bottom to make the book itself a little coffee table. In
one episode, he started Kramerica Industries, a fictitious company started
by Cosmo Kramer to develop a bladder system for oil tankers. In theory,
this bladder system would prevent the release of oil after an accident.
Unfortunately, Mr. Kramer was not successful in his attempts and
abandoned the project. Mr. Kramer had only one employee, Darren, an
intern from New York University.
Sou rce: http://encyclopedia.thefreedictiona
ry .com/Cosmo%20 Kra mer.
sNote: Your exam should consist Of' pages including the cover page, appendix, and grade tabulation
sheet. Skim the entire exam and solve the easiest problems first. Exams not returned at the end of the
period will not be graded.
PLEASE DO NOT OPEN THIS EXAM UNTIL YOU ARE
INSTRUCTED TO DO SO.
2
1. (a) For each of the following molecules (A and B), draw a Newman projection to represent
with respect to the indicated bond. 1a-c: 5 pts each box/answer
>y
'1---
l eMe
1-[.,.,_
<.
H
'1---_
Me
'-
A
H
--~.~
H
H
..(_
"
Me"
-
I
B
- - - "B - as shown
A - as shown
1. (b) For both A and B, draw Newman projections corresponding
UtJ
to the highest and lowest energy conformations.
Ul)
~A
~J
K
H
1-1
shown
Me
_
- - "-
the conformer
H
(J{~
LH!
A - lowest energy
A - highest energy
B - lowest energy
B - highest energy
1. (c) Use the appendix material to provide an estimate of the energy
difference, if one exists, between (A-as shown) and (A-lowest energy).
\.1-
I L::
. <6 S-
kcal/mol
2. In class we saw that a tert-butyl group C(CH3b can be used to effectively "lock" a cyciohexane ring in a particular
chair conformation. What is the origin of this locking effect? What about Si(CH3b and Sn(CH3b? Explain the
structural origin of their conformational preferences, relative to the C(CH3b case. Use annotated and neatly drawn
structures in formulating your answer. Consult the appendix material. No essays! 10 pts
~J~)
~./
':
q"~k
~
~
~
~Is"vt.
,
.C{~
"
H
VOW (1,~-d·III.)(~t:.\)
$t.\lI!.r{.
- S, (CMl.) 3
+-
ho.n
- SY"I ((j.I~}~ h~
t-B~
I
Uf"tth"~
bl:,0 :;, z..S~I..,t> = \.0
C#l
~W"",,~~
ICw Ift\~
~...JJt\"'....i
(
St\ \ I
(ho!-
'is
~~jhl'1 -tr,.V1)(fJ
h\~hlJ
So hlC;klj
b~"sJ
bi~~)
") '19 1)••
"7 9S6J.)
J
,.-.~S-")o
e.q"' •••.+wi -L )
~)
to~·
3
3. (a) For each molecule, draw the chair resulting from a ring flip and circle the preferred (lower energy) conformer.
8 pts, 2 pts each
C'
C
H
•.
D
D'
H
3. (b) Which pair has the greatest energy difference between the two chair conformationS?@
3. (c) The proper name for structure C is cis-1 ,2-dimethylcyclohexane.
TRUE'
~LS3)
or
C ~~-
S -c1: mef'hy 1
1
4. (a) What is the index of hydrogen deficiency for a compound whose formula is C4HgN?
4. (b) Paying close attention to stereochemical
with formula C4HgN: 6 pts
JJ
D-D'
('(dC3he~
1 pt
representation, write down a 'considerably strained' candidate structure
s-~~
~
{'~~
e.c.\j pSIr1~
~11
o«: <..d~~~~ fN/tJlt"L
~-~~l
(;~~
tv\t~,I.$ I;l~
~
~"""1'S
A
~
4
It
F~H
6. Shown at right are Newman projection
formulas for (R,R)-, (S,S)-, and (R,S)-2,3difluorobutane. a. Which is which? b. Circle any
structures that represent meso compounds. 8 pts
F
l<
H
CH3
11<R.1
~
7. Consider the following pairs of structures. Identify the relationship between them by describing them as
representing enantiomers, diastereomers, constitutional isomers, or two molecules of the same compound. 4 pts ea
HfBr
H
+H
L:fBr
F
H3
H
C
and
F
H3C
H
~f\o~
eMr"\-hOW\~
0
Br
S::tm€. VitA.
ov
HO~O
and
HO~OH
~
OH
OH
8. Mandelic acid can be purchased as the (S)(+) enantiomer from Aldrich. Complete the
Fischer projection formula for this enantiomer
of mandelic acid. 4 pts
2
I(~If
OH
OH
qb
and
fFfH
and
Br
Br
CH3
H
H
COOH
HO
H
HO ""C02H
mandelic acid
9. Muscarine is a poisonous substance found
in the mushroom Amanita muscaria. Its
structure is represented by the constitution
shown at right. Analysis shows that muscarine
has the configuration 2S,3R,5S. Write a
correct structural formula of muscarine to
illustrate this stereochemistry. 8 pts
o
muscarine
10. Draw a Fischer projection for meso-2,3-dibromobutane.
Convert t~ing
the bromines are anti to one another. Are the methyl groups gauche o~
11
UL~.B~
nl>
~l
H
~
t
at3
------
By
g('
~
.(4
11\1
BV"
..••
L-H3
to a staggered conformation in which
one another in this conformation? 4 pts
5
Chemistry 11Oa
EXAM APPENDIX / GRADE
October 2,2009
SECOND
SHEET
Name (print)_----41e--(_e--==----.:'1'---
_
Monosubstituted Cyclohexanes - Thermodynamics
H H
HH
H
I
~
H
H
H HH
Conformational
Energies (A = -t.GO, kcal/mol)
D
0.008
CN
0.2
F
0.25
C=CH
0.41
CI
0.53
0.48
CH=CH2
1.49
CH3
1.74
Br
I
0.47
i-Pr
2.21
OH
0.6
Ph
2.8
OMe
0.58
C(CH3b
4.7
OAc
0.7
Si(CH3b
2.5
NH2
1.2
1.4
Sn(CH3b
1.0
C02H
HgOAc
0.0
C02Na
2.0
MgBr
0.78
Page
Points
2
45
3
15
4
40
Total
100
Score
X=
1710