Exam 1
Feb. 19, 2002
Chm 122
60 minutes
100 points
Name:_____________________________
I agree to observe the Wake Forest
Honor Code during this exam.
Instructions: There are six questions on the following pages. Check the exam now to be
sure that you have six questions. There are two blank pages to be used as scratch paper at
the end of the exam. You may remove these pages, as needed, but all answers must
appear on the same page as the question and, where appropriate, in the designated space.
Write your name, clearly, in the space provided above.
Each question contains several parts. Be sure to completely read each question so that
you answer all parts!
Do not hesitate to ask a question if it arises.
Clearly answer each question - if it is unclear what you intended to answer, the problem
will be counted wrong. You have sixty minutes to complete the exam. I advise that you
work through the exam once answering what you know and save problems you are
unsure of for the end of the period. Exams will be collected, promptly, sixty minutes
after they are distributed.
You are expected to abide by the Wake Forest University Honor Code and the rules of
decency. Any violations of the Honor Code will be pursued through all necessary means.
Good luck.
1. Draw Newman projections, looking down the indicated bond, for the most stable and
least stable conformations of this molecule. Name this compound according to IUPAC
rules. 12 points
H
OH
Br
IUPAC Name: 4-bromo-4-methyl-3-heptanol
C3H7
H5C2
C3H7
HO
H
Br
CH 3
Br
H
C2H5
most stable
least stable
OH
CH 3
2. In the boxes provided, draw the structure of a molecule having the molecular formula
C6H10O and the functional group indicated. How many degrees of unsaturation are
present in these molecules? Of these three, identify the molecule having the most acidic
proton and write the reaction equation for the equilibrium of this molecule with aqueous
sodium hydroxide. In which direction would the equilibrium lie? 15 pts
O
OH
ketone
OCH 3
alcohol
ether
+ many others
Degrees of Unsaturation: 2
ONa
OH
+ NaOH
+ H2O
3. In each pair, indicate if the relationship is one of constitutional isomers,
conformational isomers, or stereoisomers. In each pair, circle the more stable structure.
12 pts
stereoisomers
H
H
H
Cl
H3C
OH
CH 3
H
H3C
OH
CH 3
Cl
H
H
CH 3
H
C2 H5
H
C3H7
H
H3C
H
OH
H
Ph
constitutional
H
CH 3
Ph
conformational
Ph
Ph
H
OH
stereoisomers
4. Supply the missing starting material, reagent, or product(s). If there would be more
than one product formed, write all of the products and assign major and minor products.
Where appropriate, indicate the correct stereochemistry. 24 pts
1. O3
2. Zn, H2O
O
H
H
O
Cl
KOtBu, tBuOH
major
minor
H
H2, Pt
H
HO
KMnO4
HO
Br
H
EtOH, heat
minor
major
1. 9-BBN
OH
2. H2O2, NaOH (aq.)
Cl
Cl2, EtOH
H
EtO
MCPBA
O
5. When 2,2-dimethylcyclopentanol is dissolved in concentrated sulfuric acid, three
isomeric alkenes are produced. Provide a detailed mechanism that explains the
production of all three products. Be sure to include electron-pushing arrows, all
intermediates (but not transition states), and charges. Name the major product according
to IUPAC rules. 24 pts
conc. H2SO4
OH
A
IUPAC Name of Major Product:
B
C
1,2-dimethylcyclopentene
conc. H2SO4
OH
A
C
B
H-OSO3H
OH2
H2O
+HSO4
+ H3O
H2O
H
B
H2O
H
+ H3O
A
H2O
+ H3O
H
C
6. Compound A (C7H15Br) is not a primary bromide, yet yields a single alkene
(compound B) upon treatment with sodium ethoxide in ethanol. Hydrogenation of
compound B yields 2,4-dimethylpentane as the exclusive product. Provide the structures
of A and B in the boxes provided; logical reasoning to support these structures; the type
of reaction in going from A to B; and the IUPAC names of compounds A and B, in the
space provided. 13 pts
IUPAC Name of A: 3-bromo-2,4-dimethylpentane
IUPAC Name of B: 2,4-dimethyl-2-pentene
Br
Compound A
Compound B
NaOEt
A
H2
single alkene
B
C7H15Br
EtOH
2,4-dimethyl
pentane
E2 elimination
Because E2 elimination of A yields only a single product, A must have only one type of beta
hydrogen. That is, it must be symmetrical. The structure shown below is the only one that
could eliminate to give ONLY one product.
E2
or
Br
A
These are the same
compound! B
H2
2,4-dimethyl
Any alkene with this
pentane
carbon skeleton would
hydrogenate to give
2,4 dimethylpentane.
The key is the clue that only one alkene is produced when A undergoes elimination.