Chem 2500 Final Exam 2003, December 10 th, 9:00 am to 12:00 am
You are permitted the use of a model kit and note cards which were prepared by hand, by yourself. You may
also use a periodic table. A periodic table and a table of pKas appears at the end of this paper. Answer all
questions in this booklet. Print and sign your name below. Your signature indicates that you agree not to
divulge or discuss the contents of this exam in any way until after Jan. 20th., 2004.
.
Name:
Signature:
Question One (6 marks)
Give systematic names for the following compounds. R/S configurational symbols are not necessary.
i
ii
iii
CH3
O
O
F
OCH 3
C
O
NH 2
OH
H3 C
CH3
i)
ii)
iii)
Question Two (6 marks)
For each of the following molecules, label each chiral center as R or S and double bonds as E or Z as is
appropriate.
O
CHO
O
HOH 2 C
H
H
H
CH 2 CH 2 Br
OH
CH 2 OH
H 3 CH 2 C
CH 2 OH
CN
Question Three (3 marks)
You wish to prepare an enolate anion of acetone (right side) for use as a nucleophile.
Give an example of an appropriate reagent to accomplish this, and explain how you made your choice.
H3 C
O
O
C
C
CH3
Question Four (3 marks)
For the following two species,
H3 C
CH2
i) draw them showing their correct structure showing all bonds with as many atoms in the plane of the page as
possible. All non-bonding electrons are shown.
H2 C
H2 C
C
NH
CH
Question Five (8 marks)
The following preparation was just published in the Journal of Organic Chemistry. Classify each step in the
reaction as an addition, elimination, substitution, reduction, oxidation, pericyclic or rearrangement process.
Br
CH 3
Br
CH 3
Br2, Fe, CCl4
H3C
H3C
Br
CH 2Br
NBS, CCl 4
BrH2 C
5
Br
CaCO3,
Dioxane/H 2O
Br
Br
CH(OCH3) 2
CH3 OH/H+
(CH3O) 2HC
Br
CHO
PCC
OHC
Br
CH 2OH
HOH2C
Br
Br
1) n-BuLi
2) DMF
3) H 2O
CHO
CH 2OH
CH(OCH3) 2
CH(OCH3) 2
NaBH 4, CH3OH
(CH3O) 2HC
(CH3O) 2HC
CHO
CH2OH
CH 3
N
O
O
O
CH 3
O
N CH3
OCH3
CH3O
O
O
O
O
N
H3C
O
+
O
O
LDA
O
/H
OH
Question Six (4 marks)
What is the stereochemical relationship between the following molecules: are they diastereomers, enantiomers,
constitutional isomers or identical?
i)
ii)
F
H
F
F
H
OH
H
H
iii)
H
H
F
H
iv)
CHO
HO
OH
H
OH
H
OH
H HO
H
CH 3
CH3 H 3 C
H3 C
H
H
H
H
H
H
HOH2 C
HO
OH
CHO
HO
H
OH
CH2 OH
Question Seven (4 marks)
i)
Is the equilibrium constant for the following conformational equilibrium constant greater or less than 1?
Explain your reasoning.
H
OH
OH
ii)
H
The equilibrium constant varies depending on the solvent. In polar solvents like methanol, Keq is less
than non-polar solvents like hexane. Explain.
Question Nine (6 marks)
Give a mechanism for the following acid catalyzed reaction.
H+
O
Question Ten (4 marks)
Of the following pairs of reactions, which one (if either) will be faster? Explain your reasoning and show the
structure of the product of the faster reaction.
1)
HO
Br
OH
H 2O
Br
OH
2)
Cl
CH3 S
Cl
CH3 S
Question Eleven (6 marks)
SCH 3
SCH 3
Benzaldehydes can be prepared by the solvolysis reaction of dibromomethylarenes as shown below. This
reaction is first order and works best for benzylic substrates. Give a mechanism that is consistent with this
information and explain your reasoning.
H
O
Br
C
Br
H2 O
C
H
Question Twelve (5 marks)
The allylic substrate shown below is a good substrate for both SN1 and SN2 reactions.
i) Why?
Br
Allyl Bromide
ii) Suggest an experiment that would enable you to determine which of the two mechanisms operates faster for
this kind of substrate.
Question Thirteen (4 marks)
Give the structure, showing the correct stereochemistry, of the starting material required to prepare only the
Z-alkene shown via an E2 reaction. Explain your reasoning.
?
KOt-Bu
H3 C
H
Ph
Ph
Question Fourteen (5 marks)
i)
On one of the two diagrams below (whichever is most appropriate) sketch the π* (anti-bonding) orbital
of ethylene.
H
H
C
ii)
H
H
C
H
C
C
H
H
H
Platinum forms coordination compounds with ethylene in which the Pt-C bonding is the result of
overlap of a filled d-orbital on Pt with the π* orbital of ethylene. In the diagram below, all of the Pt—Cl
bonds lie in one plane (that of the page). Given this information, which of the following structures show
the best orientation of the alkene in the complex? As part of your answer, show how the overlap
between the d- and π*orbitals occurs by adding to the Pt d orbital drawing below.
Cl
Cl
H
Pt
Cl
H
C
H
Cl
Cl
C
H
Pt
Question Fifteen (12 marks)
Pt
Cl
H H
C
C
H H
Cl
Cl
H
Pt
Cl
H
C
C
H
H
Predict the organic product(s) of the following reactions. If more than one organic product is formed, show
them all and indicate, if possible, which is/are the major products. Be careful to indicate the relevant
stereochemical results clearly (using dashed and wedge bonds where appropriate).
ii)
Br
CH 3 OH
Br
v)
CH 3CH2 OH
Br
Na (s)
vi)
NaN 3
O
vii)
O
CH3 OH, H2 SO 4