Organic Chemistry 221
Chapter 1-5 Answers
Li
••
N CH2 CH3
1. How many electrons does phosphorus (atomic number 15) have in its valence shell? 5
CH2 CH3
2. Lithium diethylamide contains both ionic and covalent bonds. Circle the ionic bonds in lithium diethylamide.
lithium diethylamide
3. Draw the orbitals of a C=C double bond. Clearly label each bond type and indicate the type of orbitals
involved in each bond.
Below right.
4. Write valid Lewis structures for each formula below.
Show all non-bonding electrons as dots.
CF2Cl2 Freon 12 (a common refrigerant)
CO2 carbon dioxide
5. Determine the hybridization for the atoms in each
structure at right.
(A) is sp3. (B) is sp2. (C) is sp3. (D) is sp3. (E) is sp.
6. The molecular formula C2H4O can be converted into three line-bond structures. Which one of the structures is not consistent with valence
rules?
H
Three bonds to the left C and five bonds to the right C.
H
N
C C O
H
NH2
H
NH2
7. Propose at least three skeletal structures that satisfy the molecular formula C3H9N
8. Indicate which of the molecules have dipole moments and
9. What is the molecular formula of vitamin C:
See Above.
O
show the expected direction of the dipole moment.
C6H8O6
HO
O
HO
Cl
Cl
Cl
Cl
O
HO
Vitamin C
N
H
alcohol
OH
10. Circle each functional group and name the family of compound in the steroid at right:C
11. Label the indicated atoms in the structure below as 1˚, 2˚, 3˚, or 4˚:
A
es ter
ketone
O
HO
O
O
OH
alcohol D
(A) is 2°. (B) is 3°. (C) is 4°. (D) is 1°.
12. Draw a pair of isomers having the formula C5H12.
(Any Two)
H
O
B
ketone alkene
(Example below left)
14. Draw a pair of isomers containing different functional groups having the formula C5H12O. (Example below right)
13. Draw a pair of isomers having the formula C5H12S.
CH2CH2CH3
SH
SH
O
OH
5-isopropyl-3-methyloctane
15. Provide proper IUPAC names for the alkane at right.
16. Draw structures corresponding to each of the following names:
1-sec-butyl-2-ethylpentane (rename properly after drawing)
3-cyclobutylpentane
CH3CHCH2CHCHCH3
CH3CH2
CH3
4-(2,2-dibromoethyl)-3,5-dichloroheptane
Br
Br
5-ethyl-3-methyloctane
Cl
Cl
17. For the following questions refer to the structure of heptane below with hydrogens labeled a-g.
hydrogens b are equivalent to hydrogens f.
hydrogens a are 1°.
hydrogens d not equivalent to any others.
a
b c
d e
f
g
CH3CH2CH2CH2CH2CH2CH3
18. Draw one conformation of 2-methylpentane in
H
H
CH3
planar
H
Newman projection looking down the 2-3 bond.
Do the same for 2-methyl-2-pentene.
H
H
CH3
H
H
H
H
CH3
H
CH2CH3
H
CH3
H
CH2CH3
H
H
19. Why are cyclobutane and cyclopentane rings puckered?
Puckering minimizes the overall strain of the molecule by reducing the torsional strain. The slight
increase in angle strain that puckering causes is more than offset by the decrease in torsional strain.
Name two common conformations of cyclohexane. chair; boat; twist boat
20. Indicate the axial or equatorial orientation of the groups in trans-1,4-dimethylcyclohexane.
Both axial or both equatorial
21. a) Label the axial and equatorial positions.
A
A
CH3
CH3
A
E
E
b) Illustrate a 1,3-diaxial strain.
E
E
E
E
A
A
A
22. Draw [3,3,1]-bicyclononane.
Three possible views are shown.
12. Assign the R and S configuration to each of the following chirality centers. Which two represent the same molecule.
CH3
Br Cl
R
S
H
H
CH3
H
Br R
CH3
R Cl
CH3 H
CH3 CH3
R
S
H
Cl
Br
H
CH3 H
R
R CH
H
3
Cl Br
13. Draw all the isomers of C3H5ClBr2 and identify any chirality centers. Draw the stereoisomers of those molecules in Fischer projection.
I came up with 9 isomers without considering stereoisomerism. Did I miss any? The circles
indicate chirality centers. Examples of the stereoisomers are shown in brackets.