STUDENT NAME: ID NUMBER LAB TIME TA NAME
CHEMISTRY 112A First Midterm February 1, 2010 1 --------------------- (6) 2--------------------- (10) 3-------------------- (4) 4--------------------- (10) 5 --------------------- (10) 6 -------------------- (10) 7-------------------- (6) 8-------------------- (10) 9-------------------- (4) 10-------------------- (12) 11-------------------- (8) 12-------------------- (10) Bonus ---------------- (5) Total -------------------(100)
1) a) Draw the Kekule structure of CO2. What is the hybridization of carbon in this compound?
O
C
O
sp-hybridized
b) The atomic number of silicon (Si) is 14. Draw the Kekule structure of SiO2.
O
Si
O
2) Assign the formal charges to the atoms of molecule A, B and C. What is the relatioship between A and B ? What is the relationship between B and C?
H
C
N
N
H
H
C
N
N
H
A
H C N N H
B
C
A and B are two resonance forms B and C are two resonance forms
3) What is the relationship between D and E?
Br Cl
Br D and E are isomers Cl
D
E
4) Name compound the following compound and draw its skeletal structure. Identify the tertiary and quaternary carbons.
CH3 H3C CH2 C CH2 CH3 CH CH3 CH3 3,3,5-trimethylheptane
H2C
quaternary
tertiary
5) a) Indicate the hybridization of all the carbon atoms of the following molecule. b) Indicate the number of hydrogen(s) on each carbon. c) Which of these carbons are in the same plan? (Write Y when they are)
5 1 2 3 4 6 7
carbon number
1
2
3
4
5
6
7
hybridization
sp3
sp
sp
sp2
sp2
sp3
sp3
number of H
13 Y
0 Y
0 Y
1 Y
1 Y
2 Y
3
C in the same plan
6) a) Draw one resonance structure for each of the following compounds.
H H O O H H
H H O O
I
I
H H CH2 CH2 H H
H H CH2 CH2
II
II
b) Very briefly explain which of these compounds is weaker the base. Both I and II have 3 resonance structures but oxygen is more electronegative than carbon, and therefore I is a weaker base than II.
7) Circle and identify the functional groups in the following molecule
O
aldehyde O ketone amine NH2
8) a) Follow the flow of electrons indicated by the curved arrows and predict the products of the reaction.
O H CH3 O H C H
b) Draw curved arrows to represent the flow of electrons in each step, and indicate the missing fragment in the box.
O CH3 CH3 O H+ C H C H CH3
C
O C H3C
+
O NH3 H3C C Br NH3 H3C
O C
+
Br
Br
NH3
9) a) Circle the higher priority group on each carbon of the double bond of the following molecules. b) Assign E or Z configuration to each molecule?
CH Br H CH2-CH3 CH2-CH2CH3 HO H3C CH2 O C CH CH3
E
E
CH3
10) a) Draw the two chair conformations of the cis-1-bromo-4-fluorocyclohexane and circle the most stable conformer, knowing that Br is much larger than F.
Br
F
F Br
Br F
b) Draw the skeletal structure, and the two chair conformations of the trans-1-bromo-4-fluorocyclohexane and circle the most stable conformer.
F F Br
Br
c) Which is the more stable isomer?
the trans-1-bromo-4-fluorocyclohexane is the most stable isomer.
11) Draw all the possible alkenes having the formula C4H8, and name them. Do not draw the same compound twice.
1-butene
cis-2-butene
trans-2-butene
methyl-2-propene
12) Draw all possible products resulting from the substitution of one hydrogen atom of the following compound by one chlorine atom. Do not draw the same compound twice
CH3 CH3 H3C CH3 CH3 H2C Cl
CH3 CH3
C CH2 C CH3 CH3
C CH2 C CH3 CH3
CH3 H3C C
CH3 CH C CH3
CH3 Cl CH3
Bonus: Draw the structure of a compound of general formula C5H12 possessing only primary hydrogen atoms.
CH3 H3C C CH3 CH3