Name: _________________________________
CHEM 332. Midterm 1
Spring 2016
Prof Mary Watson
Please write your answers clearly in the boxes provided. If your answer is illegible or
outside the box, it will not be graded. You may use the back of test pages for scratch
work.
You may use molecular models.
Use of calculators, cell phones, headphones, or any other electronic device during this
exam is prohibited.
No notes or books may be used during this exam.
You may raise your hand to ask a question if you are not sure what is being asked of
you.
There are 9 pages in this exam. Please check that your test has 9 pages before you
begin. The last 2 pages are blank and may be used as scratch paper. Page 2 contains
potentially useful IR and NMR spectral tables, as well as a periodic table.
Please circle your discussion
section:
Mon
Tues
Fri
Question
Points
1
_____ /20
2
_____ /20
3
_____ /20
4
_____ /20
5
_____ /20
Total
_____ /100
1
Name: _________________________________
Approximate IR Absorption Frequencies
Bond
O–H (alcohol)
O–H (carboxylic acid)
N–H
C–H
C≡N
C≡C
C=O
C–O
1
Approximate H NMR Chemical Shifts
Hydrogen
δ (ppm)
CH3
0.8–1.0
CH2
1.2–1.5
CH
1.4–1.7
C=C–CHx
1.7–2.3
O=C–CHx
2.0–2.7
Ph–CHx
2.3–3.0
2.5
≡C–H
R2N–CHx
2.0–2.7
I–CHx
3.2
Br–CHx
3.4
Cl–CHx
3.5
F–CHx
4.4
O–CHx
3.2–3.8
C=CH
4.5–7.5
Ar–H
6.8–8.5
O=CH
9.0–10.0
ROH
1.0–5.5
ArOH
4.0–12.0
RNHx
0.5–5.0
CONHx
5.0–10.0
RCOOH
10–13
–1
Frequency (cm )
3650–3200
3300–2500
3500–3300
3300–2700
2260–2220
2260–2100
1780–1650
1250–1050
Intensity
Strong, broad
Strong, very broad
Medium, broad
Medium
Medium
Medium to weak
Strong
Strong
13
Approximate C NMR Chemical Shifts
Carbon
δ (ppm)
Alkanes
Methyl
0–30
Methylene
15–55
Methine
25–55
Quaternary
30–40
Alkenes
C=C
80–145
Alkynes
70–90
C≡C
Aromatics
110–170
Benzene
128.7
Alcohols, Ethers
C–O
50–90
Amines
C–N
40–60
Halogens
C–F
70–80
C–Cl
25–50
C–Br
10–40
C–I
–20–10
Carbonyls, C=O
R2C=O
190–220
RXC=O (X = O or N)
150–180
2
Name: _________________________________
1. (20 points) (a) Please rank the following molecules with respect to their electrophilicity. Number the
molecules 1–3, giving 1 to the most electrophilic and 3 to the least electrophilic.
O
H
O
NMe2
H
O
Me
H
OMe
(b) Please show the relative energies of the π* orbitals of each of the molecules on the molecular
orbital energy diagram below.
E
O
H
O
NMe2
H
O
Me
H
OMe
3
Name: _________________________________
2. (20 points) Please provide the missing reagents for the following transformations. In some cases,
more than one step may be required.
O
O
NH2
NC
Me
O
O
MeO
NH2
Me
NH2
HO
Me
Me
MeO
H
N
Me
Me
O
4
Name: _________________________________
3. (20 points) Please draw the major product for each of the following reactions.
1. NaOEt
O
2.
O
Ph
EtO
OH
Br
3. H3O+
1. Na2Cr2O7, H2SO4, H2O
2. MeLi (excess)
3. H3O+
1. LiNiPr2, –78 °C
O
2.
H
O
Me
3. H3O+
O
Me
1. MeLi
2. H3O+
5
Name: _________________________________
4. (20 points) The Danishefsky lab used the following reaction sequence in their synthesis of the
natural product Hispidospermidin. Please draw a reasonable arrow-pushing mechanism for the
following reaction. Note: Each reagent was added sequentially without work-up between steps.
O
1. LiCuMe2
O
2.
H3C
3. KOH, H2O, Δ
O
Me
(all one-pot; no work-up between steps)
6
Name: _________________________________
5. (20 points) Provide a synthesis of 2 from 1. All the carbons in your product (2) must come from 1 or
an organic reagent with less than 2 carbons.
O
O
H
CH3
1
H
OH
CH3
CH3
2
7
Name: _________________________________
This page was intentionally left blank and may be used for scratch paper.
8
Name: _________________________________
This page was intentionally left blank and may be used for scratch paper.
9