Name: ______________________________ Section: _______
CHEM 331. Midterm 1
Fall 2014
Prof Donald 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 10 pages in this exam. Please check that your test has 10 pages
before you begin. The last 3 pages are blank and may be used as scratch paper.
Question
Points
1
_____ /12
2
_____ /16
3
_____ /26
4
_____ /23
5
_____ /13
6
_____ /10
Total
____
/100
Name: ______________________________ Section: _______
1. (12 points) Provide the BDE and Bond length for each of the indicated bonds:
Me
2. (16 points) Draw all reasonable resonance structures of the following
molecule.
O
NH 2
Me
Name: ______________________________ Section: _______
3. (26 points) The molecule below is a very important reagent in organic
synthesis. It is known as a carbodiimide. Indicate the hybridization state of each
non-hydrogen atom in the molecule
N
Me
C
Me
N
3a. In the space below, sketch the bonding π orbitals involved in the
carbodiimide. Be sure to clearly indicate geometric relationships as needed.
Section: _______
Name: ______________________________ 3c. In the space below, draw the molecular orbital diagram of one of the C=N
double bonds in the carbodiimide. Clearly label all AO’s and MO’s.
Name: ______________________________ Section: _______
4. (23 points) Consider the following molecule:
Me
Me
Me
a. Draw all chair conformations of the above molecule.
b. Label which chair conformation is the most stable.
c. In less than 20 words, please rationalize why the low energy conformer is
more stable. You do NOT need to estimate specific energy values.
Name: ______________________________ Section: _______
5. (13 points) Consider the following molecule
Me
N
H H
N
N
N
N
N
H H
Me
a. For the above molecule, clearly label each stereocenter with an asterisk and
assign it as (R) or (S) configuration.
b. Assuming there is no hindered bond rotation, is this molecule chiral? Explain
why or why not in 2 sentences or less.
Name: ______________________________ Section: _______
6. (10 points) The following molecule is 2-Pentanol.
OH
Me
Me
a. Draw the molecule in the (S) configuration.
b. Draw the newman projection looking down the C2-C3 bond.
Section: _______
Name: ______________________________ This page was intentionally left blank and may be used for scratch paper.
Section: _______
Name: ______________________________ This page was intentionally left blank and may be used for scratch paper.
Section: _______
Name: ______________________________ This page was intentionally left blank and may be used for scratch paper.
Name: ______________________________ Section: ______
CHEM 331. Midterm 1
Fall 2014
Prof Donald 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 10 pages in this exam. Please check that your test has 10 pages
before you begin. The last 3 pages are blank and may be used as scratch paper.
Question
Points
1
_____ /12
2
_____ /16
3
_____ /26
4
_____ /23
5
_____ /13
6
_____ /10
Total
____
/100
Name: ______________________________ Section: ______
1. (12 points) Provide the BDE and Bond length for each of the indicated bonds:
Me
2. (16 points) Draw all reasonable resonance structures of the following
molecule.
O
OH
Me
Name: ______________________________ Section: ______
3. (26 points) The molecule below is a very important reagent in organic
synthesis. It is known as ethyl isocyanate. Indicate the hybridization state of
each non-hydrogen atom in the molecule
O
C
Me
N
3a. In the space below, sketch the bonding π orbitals involved in the isocyanate.
Be sure to clearly indicate geometric relationships as needed.
Section: ______
Name: ______________________________ 3c. In the space below, draw the molecular orbital diagram of the C=N double
bond in the isocyanate. Clearly label all AO’s and MO’s.
Name: ______________________________ Section: ______
4. (23 points) Consider the following molecule:
Me
Me
Me
a. Draw all chair conformations of the above molecule.
b. Label which chair conformation is the most stable.
c. In less than 20 words, please rationalize why the low energy conformer is
more stable. You do NOT need to estimate specific energy values.
Name: ______________________________ Section: ______
5. (13 points) Consider the following molecule
Me
N
H H
N
N
N
N
N
H H
Me
a. For the above molecule, clearly label each stereocenter with an asterisk and
assign it as (R) or (S) configuration.
b. Assuming there is no hindered bond rotation, is this molecule chiral? Explain
why or why not in 2 sentences or less.
Name: ______________________________ Section: ______
6. (10 points) The following molecule is 2-Bromopentane.
Br
Me
Me
a. Draw the molecule in the (R) configuration.
b. Draw the newman projection looking down the C2-C3 bond.
Section: ______
Name: ______________________________ This page was intentionally left blank and may be used for scratch paper.
Section: ______
Name: ______________________________ This page was intentionally left blank and may be used for scratch paper.
Section: ______
Name: ______________________________ This page was intentionally left blank and may be used for scratch paper.