CHE 230-002 – Organic
Chemistry
Exam 1,
Name
________________________________ Student ID Number ________________
Before you begin this exam: First: Note
the blank page at the end provided for scrap paper. It must be returned at the end of the
exam. Second: Place your student identification on your desk. A proctor will come around to check
everyone’s ID. Third: Read through the entire exam. Do not waste time on problems that you can’t
do if there are others that look easy. Fourth: It is critically important that
your answers be written in a clear, unambiguous manner. Answers in which your
intentions are unclear will not receive credit.
Fifth: Read
the instructions for each problem.
You will have until
Problem Points Score
1a. 8 _____
1b. 5 _____
1c. 8 _____
2. 6 _____
3. 12 _____
4. 4 _____
5. 6 _____
6. 8 _____
7. 10 _____
8. 9 _____
9. 6 _____
10. 6 _____
11. 6 _____
12. 6 _____
Total 100 _______
1. (8+5+8=21) Consider the linear molecule, acetonitrile N-oxide, CH3CNO.
(a) Draw a Lewis structure for the most stable resonance form for this molecule. Show lone pairs and formal charges.
See KEY for Exam 1 section 001
(b) Draw the next most stable alternate resonance form.
See KEY for Exam 1 section 001
(c) Assign hybridization to the four hybridized atoms in this linear neutral molecule by writing the appropriate abbreviation, sp3, etc., below each atom below.
C ──── C ───── N ───── O
_____ _____ _____ _____
See KEY for Exam 1 section 001
2. (6) Using Newman projections, draw a non-eclipsed (staggered) conformation of 2,3-dimethylbutane that is not the most stable (i.e. the next most stable conformation).
See KEY for Exam 1 section 001
3. (a) (3) How many degrees of unsaturation does C3H2O have? __three_____
(b) (9) Draw three structural isomers of C3H2O . None may have formal charges. All must obey the octet rule.
There are others.
4. (4) Assume that the heats of formation of A-D below are all negative. Circle the alkene below with the most negative heat of formation.
A is the most highly substituted
alkene and the most stable.
5. (6) How many 13C NMR signals are expected for each of the molecules below. Write that number on the line below each structure.
_three_ _two_
6. (8) Circle all the chiral molecules among those shown below.
|____________________________|
The third, fourth and fifth structures lack
a plane of symmetry and are therefore chiral
7. (10) Using asterisks identify all the stereogenic sp3 hybridized atoms in the molecule below.
See the KEY for section 001
8. (9) Four terms of stereochemical relationship are listed below. They are followed by three pairs of molecules. For each pair of molecules choose the term that describes the relationship shown in that pair. Write the appropriate capital letter on the line under the pair of molecules.
A. enantiomers (configurational)
B. diastereomers (configurational)
C. structural (or skeletal) isomers
D. identical
E. not isomers
___A - enantiomers__ __B - diastereomers___
(c)
_C – structural isomers_
9. (6) In the underlined spaces provided in the name, add the correct stereochemical labels (R, S, E, or Z) to the name of the molecule shown below.
(2_S_,4_R_)-2,4-dichlorohexane.
10. (6) Write the major organic product formed in the reaction below.
11. (6) Draw the structure of an alkene that could be used to form the molecule below.
12. (6) Draw an orbital picture for carbon dioxide, CO2 . The order of connectivity is O-C-O. Show the correct geometry with solid lines for hybrid orbitals in the plane, wedges for hybrid orbitals coming out from the plane, and dashed lines for hybrid orbitals extending behind the plane of the paper. Show p orbitals by drawing the top and bottom lobes for each.
