Name ________________________
Final Exam SOLUTION
Please work and place your answers in the spaces provided. Show your work for maximum credit!
The last page may be torn off and used for scratch paper. Bring all material up when you are finished.
Bonne chance!
1. Nomenclature. [12]
a. Name the following compounds, using IUPAC or common naming technique.
(3S, 4S) – 1,4 – dibromo – 3 - isopropylpentane
Br
Br
F
(3Z, 5Z) – 3 – ethyl – 2 – fluoro – 1,3,5 – heptatriene
CH3
H
Cl
H
Cl
CH3
meso – 2,3 – dichlorobutane -or(2S, 3R) – 2,3 – dichlorobutane
b. Draw the following compounds from the IUPAC names.
(2R,4R)-4-bromo-2-iodopentane
trans-1-bromo-3-t-butylcyclohexane
I
Br
(2E, 4Z)-5,6,7-trimethyl-2,4-octadiene
Final
Fall 2005
Page 1 of 9
Chemistry 211
Clark College
2. Predict the products for the following reactions. Indicate stereochemistry, where appropriate. [10]
CH3CH2OH
H+ (cat.)
OCH2CH3
1) Hg(OAc)2,
H2O
2) NaBH4
OH
Br
HBr
H2O2
1
2
3
4
5
Br
1) O3
2) (CH3)2S
O
O
H
Cl
Cl2
CH2Cl2
Cl
3. For each molecule below, draw both chair conformers. Circle which conformer is the most stable
conformer. Be sure to draw in the hydrogen atoms on the substituted carbons and clearly
distinguish between equatorial and axial positions. [6]
Br
H
H
H
Br
Br
H
F
H
F
CH3
CH3
Exam 3
H
H
CH3
H
CH3
CH3
H
F
Fall 2005
H
CH3
Page 2 of 9
Chemistry 211
Clark College
4. a. Using curved-arrow notation, give the complete mechanism for the following reaction. Include
all necessary arrows, formal charges, etc. [10]
H2O
(cat.)
H+
OH
H
H
O H
H
H
H
H
H
H2O
Intermediate 1
H O
H
H
OH
H2O
Intermediate 3
Intermediate 2
b. On the axes below, sketch a reaction energy diagram for your mechanism above. Label the
axes, reactants, intermediates and product. Be sure to indicate the relative energies of the
various steps. Indicate the rate-determining step, and show how ∆Hrxn could be obtained from
your diagram.
RDS - highest energy transition state
Int 1
Int 2
E
R
!Hrxn
Int 3
P
Reaction Coordinate
Exam 3
Fall 2005
Page 3 of 9
Chemistry 211
Clark College
5. Label each of the following pairs of molecules with the most accurate possible term, choosing from
constitutional/structural isomers, enantiomers, diastereomers, identical molecules or “just
different.” [8]
a)
These two compounds are structural isomers- they both have
the same molecular formula (C6H12).
b)
These compounds are identical! Even though they are drawn
differently, because the molecule has symmetry, it is not chiral.
c)
Because there are two stereocenters, and one has the same
chirality and the other is different, these two compounds are
diastereomers – they are non-superimposable, non-mirror
images.
d)
OH
These molecules are enantiomers – non-superimposable mirror
images.
OH
Br
H
H3C
Br
H
CH3
6. For each molecule below, circle the most acidic hydrogen(s) (draw it/them in if necessary). For the
pair of molecules, put a box around the most acidic molecule, explaining your choice in 15 words or
less. Draw the conjugate base, including any resonance structures (if applicable), of the most
acidic molecule. [10]
OH
OH
Cyclohexanol
Phenol
Once the conjugate base forms, the negative charge on the oxygen can be delocalized through the ring
with resonance.
O
Exam 3
O
O
Fall 2005
O
O
Page 4 of 9
Chemistry 211
Clark College
7. Rank the following molecules in order of acid strength, where 1 = weakest acid and 4 = strongest
acid. [4]
O
O
+
H
O
OH
3
OH
HO
O
3
4
1
2
8. Complete the reaction given, and determine Keq for the reaction (you may leave it as 10XX). Is this
reaction spontaneous as written? The pKa of ethyne is 25, and the pKa of ammonia is 38. [6]
H3C
+
H
NaNH2
Na+
H3C
25
+
NH3
38
pK eq = 25 - 38 = -13
K eq = 10
-pK eq
= 10-(-13) = 10 +13
Keq =
1 x 10+13
Spontaneous?
Definitely!
9. Draw Newman projections for the most stable and least stable staggered conformations, and the
least stable eclipsed conformation, for the C2-C3 bond of 2-methylbutane and label them. [8]
2-methylbutane
H
H
H3C
H
CH3
H3C
H
H
H3C
H
CH3
Most stable - staggered
Exam 3
CH3
Least stable - staggered
Fall 2005
HH
H3C
H3C
CH3
H
Least stable - eclipsed
Page 5 of 9
Chemistry 211
Clark College
10. Using the scale below, sketch the NMR for ethyl methyl ether. Be sure to put in approximate
chemical shift values, the correct splitting patterns and indicate what the integration would be for
each peak. Indicate which peak corresponds to which hydrogens on the molecule. [4]
H3C
O
C
H2
CH3
ethyl methyl ether
3H
singlet
3H
triplet
2H
quartet
5
4
3
2
1
0
Chemical shift, ppm
Exam 3
Fall 2005
Page 6 of 9
Chemistry 211
Clark College
11. Determine the structure for C10H12O2, from the NMR below. Label the spectrum by placing letters
beside each unique group in your structure, and labeling the peaks that correspond with the
appropriate letter. [6]
3H
3H
2H
Both peaks
integrate to
4H total
[2H + 2H]
The index of hydrogen deficiency = 5.
With such a high index, I suspect a benzene ring – 3 double bonds and 1 ring gives an index of 4. To
verify this, look in the region between 7 and 8 ppm.
Final Structure
for C10H12O2 =
H3C
singlet, 2.4 ppm
Exam 3
Fall 2005
O
O
quartet
2H
4.4 ppm
triplet
3H
1.4 ppm
Page 7 of 9
Chemistry 211
Clark College
12. Match each compound to its IR spectrum. [8]
O
OH
O
H
OH
H3C
A
B
C
D
No C=C or
C=O
O-H
sp3 C-H
Compound: Compound C
Aldehyde C-H
C=O
sp3 C-H
Compound: Compound A
C=C
2
O-H
3
sp sp
C-H’s
Compound: Compound D
sp3 C-H
C=O
Compound: Compound B
Exam 3
Fall 2005
Page 8 of 9
Chemistry 211
Clark College
Multiple Choice. Circle the choice that best answers the question or completes the statement. [2 ea]
13. Which of the following resonance structures is the least important contributor to the overall structure
of the acetate ion?
O
H3C
O
O
H3C
H3C
O
O
O
O
H3C
O
A
B
C
D
Too many charges, positive charge on more electronegative atom.
14. What is the maximum number of stereoisomers possible for S-adenosylmethionone, a popular
dietary supplement (SAMe)?
NH2
O
NH2
HO
* * N
S
5 stereocenters = 25 isomers!
*
*
*
N
N
O
HO
OH
a. 23
b. 24
c. 25
d. 26
15. Calculate the Index of hydrogen deficiency for Testosterone, C19H26O2.
a. 5
b. 6
c. 7
d. 8
e. none of these
16. Which of the following substances does NOT function at a Lewis Acid?
a. (CH3)3C+
b. (CH3)3N
c. BF3
The only one with a lone pair, all others have empty orbitals.
Exam 3
Fall 2005
d. AlBr3
Page 9 of 9