Name:
CHEMISTRY 249S
Examination 1
February 13th 2006
Answer all questions in the spaces provided on the examination sheets,
indicating clearly what is to be graded.
PRINT YOUR NAME AND STUDENT NUMBER
CLEARLY ON THE FIRST PAGE OF THE EXAM BOOKLET
NAME:
STUDENT NUMBER:
NMR Spectroscopic Correlation Tables are provided on Pages 9-10
of this booklet.
Allowed Aids: Molecular Models
Calculators and other electronic devices are not permitted in this examination
Credit will be given for partial answers
WAIT UNTIL YOU ARE TOLD TO BEGIN
Marking Scheme
Good Luck!
Question 1
15
Question 2
25
Question 3
25
Question 4
60
Total
125
1
Name:
1. (15 Points) Shown below is the chemical structure of cocaine. Answer the following
questions about the structure of this compound.
CH3
O
H3C
O
N
O
O
(a) How many chiral centres are there in this molecule?
(b) How many methylene group signals would you expect to see in the DEPT NMR?
(c) How many aromatic carbon signals (peaks) would you see in the 1 3C NMR?
(d) What is the most downfield signal you would expect to see in the 1 H NMR? Indicate this on
the structure above by drawing an arrow to the hydrogen.
(e) What is the most downfield signal you would expect to see in the 1 3C NMR? Indicate this
on the structure above by circling the carbon.
(f) What splitting pattern (multiplicity) would the N-methyl group (the methyl group attached to
the nitrogen atom) show in the 1 H NMR?
2
Name:
2. (25 Points) What are the final products of the following reactions? You should clearly indicate
the selectivity of the reactions?
(a)
SO3 / H2SO4
(b)
Cl
Br2 / FeBr3
(c)
Cl / AlCl3
(d)
OCH3
HNO3 / H2SO4
CH3
(e)
Cl
Cl
CH3S
(1 equiv.)
3
Name:
3. (25 Points) Answer the following questions about the reaction shown.
O
O
Cl
/ AlCl3 (1.1 equiv)
(a) Draw a full mechanism for this transformation. Your answer should include curved arrows
to show electron movement.
(b) Why are 1.1 equivalents of the catalyst needed for this reaction? What work-up step must
be employed as a result?
(c) Why is this reaction more selective than the Friedel-Crafts alkylation reaction?
(d) What reagents would you use to reduce the carbonyl functional group to a CH2 group?
4
Name:
4. (60 Points) The spectral data for three unknown compounds, A, B and C, are given on the next
3 pages. Deduce the structures for the unknown compounds. Please note, even if you cannot
deduce the final structures, marks will be given for fragments of those structures or your deductive
reasoning. Also, only 2 and 3-bond couplings are given in the 1 H NMR spectra.
COMPOUND A:
COMPOUND B:
COMPOUND C:
5
Name:
COMPOUND A
Molecular Formula = C8H8O3
IR
3288 cm-1
(br)
1680 cm-1
1
H NMR
2H (d,
J=8.0Hz)
2H (d,
J=8.0Hz)
3H (s)
1H (s)
δΗ (ppm)
13
C NMR
5 peaks
1 peak
δC (ppm)
6
Name:
COMPOUND B
Molecular Formula = C6H11N
IR
2262 cm-1
1
H NMR
6H (d, J=6.0 Hz)
3H (m)
2H (t, J=7.5 Hz)
δΗ (ppm)
13
C NMR
DEPT NMR δC (ppm)
(only protonated C's
are listed)
34.1
27.3
21.8
15.1
δC (ppm)
7
CH
CH2
CH3
CH2
Name:
COMPOUND C
Molecular Formula = C6H10O
IR
1696 cm-1
1
H NMR
1H (d,
J=7.5 Hz)
1H (dt,
2H (m)
J=15.5, 6.5 Hz)
1H (dd,
J=15.5, 7.5 Hz)
3H (t,
J=7.0 Hz)
2H (q,
J=6.5 Hz)
δΗ (ppm)
13
C NMR
δC (ppm)
8
Name:
Proton Chemical Shifts
δ (p.p.m)
13
12
11
10
9
8
7
6
5
4
3
2
1
0
O
(carboxylic
acid OH)
(phenol OH) Ar
O
O
H
H
N
(amide NH)
H
O
(alcohol OH) R O H
N
(amine NH)
O
(aldehyde H)
H
(carboxylic
acid H)
H
(aryl or
aromatic H)
(vinylic or
alkene H)
H
O
O
H
(X=Halogen) X
R/H
O
H
H
N
H
O
(alpha
carbonyl H)
H
(benzylic H) Ar
(alkyne H)
H
H
(allylic H)
Alkane CH
13
12
11
10
9
8
7
6
5
δ (p.p.m)
9
H
4
R
3
H
2
1
0
H
Name:
Abbreviations for proton multiplicities: s=singlet, d=doublet, t=triplet, q=quartet, m=multiplet.
Higher multiplicities are given in full i.e. quintet, sextet, septet, etc.
Coupling Constants (J values)
Alkene Protons:
Aliphatic Protons:
H
3
J ≈ 6 - 7 Hz for freely
rotating systems (i.e. chains)
H
2
φ
10 Hz
C
H
H
H
H
J ≈ 0 - 4 Hz
3
H
J ≈ 4 - 14 Hz 3J ≈ 11 - 20 Hz
cis
trans
Aromatic Protons:
8 Hz
H
H
H
H
3J
H
H
H
0 Hz
0°
0 Hz
180°
90°
H
dihedral angle, φ
13
3
4
J ≈ 6 - 9 Hz
5
J ≈ 0 - 3 Hz
H
J ≈ 0 - 1 Hz
C Chemical Shifts
δ (p.p.m)
220
200
180
160
O
C
140
120
100
80
60
40
20
0
(aldehyde or ketone
carbonyl C)
O
C
(nitrile C)
C
O/N
(carboxylic acid
derived carbonyl C)
N
C
(alkenyl or
alkene C)
C
C
C
C
C
C
(aryl or aromatic C)
C
C
(alkyne C)
C
O
C
N
X
C
C
R/Ar
220
200
180
160
140
120
100
δ (p.p.m)
10
80
60
40
20
0
C