FINAL EXAMINATION
Organic Chemistry, Chem 220a
9 A.M.; Saturday, December 12, 2009
NAME (print): ______________________________________________________________
TA:_____________________ Section Day:_____________
Section Time:______________
Take a few moments to look over the
exam. Do problems first with which
you are most comfortable.
Important points and unknowns are in bold type. Do all preliminary work on the worksheets. The worksheets will not be graded.
The exam is the length of two hour exams with an additional one hour for
review. STOP writing when you are asked to do so. Put your name on the cover
sheet and subsequent pages (except for
Work Sheets) where indicated.
There is a Periodic Table on page 15.
.Remember: Neatness is to your advantage.
Have a GREAT winter
break!
1. Spectroscopy/Structure I (30
pts) ________
2. Reactions I (30 pts; 5 of 6) ________
3.
Potpourri (48 pts; 8 of 10)
________
4. Structure II (30 pts.) ________
5. Synthesis ( 30 pts.) ________
6. Reactions II (30 pts.; 5 of 6) ________
7. The Standard State/Structure (30 pts.) ________
8. Concepts (22 pts.; 1 of 3) ________
______________________________________________
Total (250 pts)
1. Spectroscopy/Structure I: (30 pts.) Compound A
(M+ = 86), whose infrared
spectrum is shown (Fig. 1, pg. 3), reacts with one equivalent of Grignard
reagent B (RMgBr) to form
compound C (IR: Fig. 2, pg. 3),
whose mass spectrum displays a molecular ion at M+ = 102. Compound C reacts readily with catalytic H2SO4 to give three isomers (D, E
and F), two of which are
stereoisomers. Compounds D and E
both form two products upon ozonolysis and dimethyl sulfide reduction, namely, G
(C4H8O) and H (C2H4O). Compound
G is inert to aqueous chromic
acid. Compound D liberates less heat upon combustion than does E. Vigorous permanganate oxidation of F forms A
and CO2. What are the
structures of A – H? Show your reasoning.
Fig. 1
Fig. 2
2. Reactions I: (5 x 6
pts. = 30 pts.) Do 5 of
6. Provide structures for the unknown
compounds. Be explicit about stereochemistry, optical activity, racemates, etc.
No
mechanisms required! If you do more than five problems, cross out
(with a large X through the solution) the one that you do not want graded.
Écontinued
3.
Potpourri: (8 x 6 pts. =
48 pts.) Do 8 of 10 problems. If you do more than eight problems,
cross out (with a large X through the solution) the ones that you do not want
graded.
a) Circle the reagent(s) that will efficiently convert
3-hexene into propionaldehyde.
cat. OsO4/H2O2 HIO4 OsO4/cat.
HIO4 cat.
OsO4/ HIO4 O3/(CH3)2S
b) Given the DHfo
of CO2 (-94.05 kcal/mol), H2O (-68.3 kcal/mol) and
acetylene (+54.5 kcal/mol), determine the heat of combustion of acetylene (C2H2). Show work.
c) Provide a sketch of the
molecular ion(s) in the mass spectrum of
1,2,3-tribromobutane.
Include the masses and intensities of the peaks. Show work.
d) The heat of combustion
of n-octane is –1308
kcal/mol. Predict the heat of
combustion of n-decane.
Show work.
e) Circle the
functional group that has the lowest energy carbonyl frequency (cm-1)
in its infrared spectrum.
RCOCl RCO2R
RCHO
R2CO
RCONH2
f) Cholesterol contains 27 carbons, a secondary alcohol, a
double bond and four rings. What
is its molecular formula? Show
work.
g) A solution of a 2:1 mixture of meso- and (R, R)-tartaric acid ([a]D = +12o) will display what specific
rotation? Show work.
h)
|
New York Times, Science Times, 10/19/09
How Tongues Taste the Carbonation in a Fizzy
Beverage Published: October 19, 2009 ÒAside
from the natural and artificial flavors and sweeteners, soda and other fizzy
beverages have a distinct carbonated taste. It is difficult to describe, but
you know it is there when tiny bubbles of carbon dioxide go crazy all over
your tongue.Ó WhatÕs wrong with this picture? What can you tell the author and
graphic artist about CO2 to improve the presentation? |
continued
É
i) Circle the greatest number of structures that are at the
same oxidation level.
j) The compound C17H26Br2ClN3O3S
absorbs four equivalents of hydrogen.
How many rings are present in the compound? Show work.
4. Structure II: (30
pts.) Optically active ester A,
C10H20O2, reacts with excess Grignard reagent B (RMgBr) to form (R)-C (C9H20O) and (S)-D (C5H12O). Compound C is inert to PCC oxidation but D forms E
(C5H10O) with this reagent. Exposure of compound C to catalytic H2SO4
readily leads to optically
inactive F (C9H18),
the major E1 product.
Reduction of A with LiAlH4
affords (±)-D. What are the structures of A-F? Explain and illustrate.
5. Synthesis: (30
pts.) A chemist wishes to
synthesize 3-undecanone specifically labeled with deuterium at C6
to study the fragmentation pattern of alkyl ketones in the mass
spectrometer. She has at her
disposal 1-hexanol, ethylene, and 1-propanol as sources of carbon to become
incorporated into 3-undecanone.
She also has available D2O and LiAlD4 as
deuterium sources and all other necessary reagents. She designs a synthesis of 3-undecanone-d2. What is her strategy? |
|
6) Reactions II: (5 x 6 pts. = 30 pts.) Do 5 of 6. Provide reagents for the chemical
transformations. Several steps may
be required. Additional sources of carbon may be required. If you do
more than five problems, cross out (with a large X through the solution) the
one that you do not want graded.
Écontinued
7. Standard State/Structure: (30 pts.) Three achiral
and non-racemic isomers A, B
and C, two of which (A and B)
are stereoisomers, all give the
same alkane D (M+ =
86) upon the uptake of one equivalent of hydrogen. The absolute difference in the heat of combustion of A and B
is 0.6 kcal/mol (not 1.0 kcal/mol, which
will eliminate two possible carbon skeletons) with A liberating more heat than B upon hydrogenation. The acid-catalyzed isomerization of C to B
liberates -2.0 kcal/mol of heat.
The heats of formation of C
and D are
-13.4 kcal/mol and -41.0
kcal/mol, respectively: a) Draw a
Standard State diagram that employs the data given and shows the structures of A-D. b)
Determine the heats of formation of A and B. c) What are the
heats of hydrogenation of A and B? Show work. [Hint: What are the possible carbon skeletons for D? Which
one, working backwards, can only be derived from A, B
and C given the information
provided?]
8. Concepts: (22
pts.) Do 1 of 3. If you do more than one problem, cross
out (with a large X through the solution) the ones that you do not want graded.
a) Explain and illustrate an
example of the role that isotopic labeling plays in establishing the mechanism
of a chemical reaction we have studied.
b) Using energy diagrams and
commentary, distinguish between a kinetic (E2) and a
thermodynamically (E1) controlled reaction. Be sure to indicate which energy
differences are relevant. Use an
example of your choosing.
c) Explain and illustrate an
example of a stereospecific reaction.
How does it differ from one that is stereoselective?
Work Sheets
Work Sheets