Name:
Chem 114
Hour Exam I
1. The antibiotic thiarubin-A was discovered by studying the feeding habits of wild
chimpanzees in Tanzania. The structure of thiarubin-A is:
A. (2 points) Complete the above Lewis structure by showing all missing pairs of
electrons There should be 2 lone pairs on each of the sulfurs
B. (6 points) This molecule contains 13-C and 2-S atoms. How many of these atoms
are
sp hybridized ? 6C 0S
sp2 hybridized ? 6C 0S
sp3 hybridized ? 1C 2S
dsp3 hybridized ? 0
d2sp3 hybridized ? 0
C. (2 points) How many sigma (F) bonds are there in this molecule?
23
D. (2 points) How many pi (B) bonds are there?
9
2. (13 points) What is a sigma (F) bond? What is a pi(B) bond? When you hybridize
the 1s orbitals from 2 atoms together you get 2 new bonds, a F and a F* . When you
hybridize the 2p orbitals from two atoms together you get 6 new bonds one F, one F*,
two B and two B* bonds. Explain both the number of bonds that you get, and why they
have different geometries.
A F bond is a covalent chemical bond with the electrons located along a line
connecting the atoms, in the B bonds the electrons are located on either side of the line
connecting the atoms. When you hybridize 2 - s orbitals together (1 from each atom)
you get two new molecular orbitals, and these orbitals have their electrons located
along the line connecting the atoms so they are F bonds (a picture like figure 19.25 is
helpful)
When you hybridize p orbitals together (3 from each of 2 atoms) you get 6 new
orbitals. Four of these orbitals have their electrons located on either side of the line
connecting the atoms so they are B orbitals, while 2 of the molecular orbitals have
electrons along the line connecting the atoms so they are F bonds (A figure like 9.33 is
helpful)
2
3. (13 points) Use the molecular orbital model to write the electron configuration of the
following diatomic species: C2, C2+, and C2-. What is the bond order of each of these
species? Which is the most stable? The least stable? Which has the longest bonds
length and the shortest bond length? Which species are diamagnetic, which are
paramagnetic?
C2
C2+
C2F*2p
__
__
__
B*2p
__ __
__ __
__ __
F2p
__
__
8_
B2p
8988
899
9889
F*2s
98
89
98
F2s
98
89
98
Bond Order
(6-2)/2=2
(5-2)/2= 1.5 (7-2)/2=2.5
diamaganetic Paramagnetic Paramagnetic
Stability
medium
low
high
Length
medium
longest
shortest
4. (12 points) Below are the names of four organic compounds. Write a reasonable
structure for each for these compounds. One or more of these compounds may be
incorrectly named. Identify and incorrect name and give the correct name for this
compound
2-chloro-3-ethylbutane
5-methylcyclohexanol
3-methyl-2-pentanone
Cis-1,2-dimethylnonene
3
5. (12 points) Below are structures of four different organic molecules. Give the correct
name for each compound.
1,2,4-trimethylcyclopentane
3,5-diehtyl-2-methylheptane
2-chlorohexanol
5-methyl-3-heptyne
6. (13 points) In class we learned that proteins were amino acids connected together to
from a polymer. The interesting thing about this polymer is that because there are 20
different amino acids, and each amino acids is build differently, we can make a polymer
with lots of different functional groups to do chemistry with. Below is a short, 4 amino
acid protein. Identify as many different functional groups as possible on this molecule
(Note some C’s are not drawn in to make picture clearer)
4
7. (13 points) In class I talked about six different recyclable plastics. Name at least four
of these plastics, and give both their monomer and polymer structure. (+1 extra credit
point if you can name their recycle number)
#1 PETE Polyethylene terephthalate
#2 HDPE High density polyethylene
#4 LDPE Low density polyethylene
#3 PVC Polyvinylchloride
#5 PPE Polypropylene
#6 PS
Polystyrene
8. (12 points) I want to synthesize 1-chloroethane. How would I do this if my starting
material was ethane? How would I do this if my starting material was ethene? If the
starting material was ethyne?
CH3-CH3 +Cl2
CH2=CH2 + HCl
6(substitution with light) CH2CLCH3 + HCl
6(addition with catalyst CH2CLCH3
CH/CH + H2 6(addition with catalyst) CH2=CH2 + HCl 6
(Second addition with catalyst)
CH2CLCH3