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Organic Compounds:
A First Look
Multiple Choice
1. Which one of these compounds is a water soluble solid?
a. CCl4
b. CH2Cl2
c. CaCl2
d. BCl3
e. graphite
ANS: c
2. Which structures represent the same compound?
a.
H
CH 3 CH 2 — C — CH 2 CH 3
b.
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CH 3
H
CH 3 CH 2 CH 2 — C — CH 3
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CH 3
H
H
H
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H
H
H
H
C
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H—C—C—C—C—C—H
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H
H
C
H
H
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H
H
H
H
H
H
H
H
H
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H—C—C—C—C—C—C—H
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c.
H
H
C
H
H
H
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H
H
H
d.
e.
ANS: c
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14
Organic Compounds: A First Look
3. Which structures represent isomers?
CH 3
|
a.
CH 3 CH 2 CH CH 2 CH 3
CH 3 CH 2 CH CH 2 CH 3
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CH 3
b.
c.
H
H
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H—C—C—
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d.
H
C
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H
H
H
e. all of the above
H
H
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C—C—H
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H
C
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H
H
H
H
H
H
H
H
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H—C—C—C—C—C—H
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H
H
H
C
H
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H
H
H
ANS: b
4. Which of the following represents a valid bonding situation?
H
H
H
C—
— C
H
a.
H
C — C
|
|
H
H
d.
e. none of the above
ANS: c
H
H
b.
H
C
H
C— C
H
H
H
H
H
H
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— C—H
C—
|
H
c.
Chapter 2
5. Which of the following is not a correct structure?
H
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N
N
||
C
H
CH
3
H
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H—C—N—N
+
b.
H
a.
+
H—O—H
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H
d.
O
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C
CH
2
H
CH
3
N
|
H
c.
NH
||
H 2N
NH 2
e.
ANS: b
6. Which structure(s) is (are) valid?
O
||
HO — S — OH
||
O
a.
F
H
|
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F —B—N—H
- |
| +
F
H
b.
OH
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HO — P — OH
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OH
c.
d. a and b
e. a, b, and c
ANS: d
7. Predict which is the strongest bond.
O —O
a.
ANS: c
C —C
b.
C—C
c.
C —H
d.
Si — Si
e.
15
16
Organic Compounds: A First Look
8. Which group of bonds is not listed in order of increasing bond length (shortest to longest)?
C—C
C—
—C
C—
—C
C—N
—N
C—
b.
C—N
C— I
C—C
C—
—C
e.
C—
—C
a.
C—N
C—N
d.
C—F
C — Cl
c.
C — Br
ANS: a
9. Which compound has a degree of unsaturation (DU) of three?
a. C5H9Br
b. C6H6O
c. C7H8Cl2
d. C8H15Cl
e. C9H12
ANS: c
10. The intermolecular interactions between molecules of CH3CH2OH include
a. Ion-dipole
b. Hydrogen bonding
c. Dipole-dipole
d. b, c
e. a, b, and c
ANS: d
11. Given a compound which dissolves in a non polar solvent like pentane, which intermolecular forces are
possible that should contribute to the solubility of the compound (in pentane, CH 3CH2CH2CH2CH3)?
a. Ion-ion
b. Ion-dipole
c. Dipole-dipole
d. Dipole-induced dipole
e. Instantaneous dipole-induced dipole (London forces)
ANS: e
12. Hydrogen bonding can be an example of which interaction(s)?
a. Ion-dipole
b. Dipole-dipole
c. Dipole-induced dipole
d. a, b
e. a, b, and c
ANS: d
Chapter 2
13. Which of these compounds would exhibit dipole-dipole intermolecular forces?
a. BF3
b. CH3CH2CH3
c. CCl3CCl3
d.
e. CH3CF3
ANS: e
14. Which of these compounds would exhibit hydrogen bonding for intermolecular forces?
CH3CH2F
a.
CH3CH2OCH3
b.
CH3CH2CH2CH3
d.
CH3CH2CH2NH2
e.
CH 3 N CH 3
|
CH 3
c.
ANS: e
15. Which compound would have the highest boiling point?
ANS: d
CH3CH2CH2CH2F
a.
CH3CH2OCH2CH3
b.
CH3CH2CH2CH2OH
d.
CH3OCH2CH2CH3
e.
CH 3 CH CH 3
|
CH 3
c.
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18
Organic Compounds: A First Look
16. Which compound would exhibit the highest melting point?
CH 3
|
H3 C — C —
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CH 3
a.
CH 3
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C — CH 3
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CH 3
CH3CH2CH2CH2CH2CH2CH2CH3
b.
CH 3
CH 3
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CH 3 CH CH 2 CH 2 CH CH 3
c.
CH 3 CH 2 CH 2 CH 2 CH 2 CH CH 3
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CH 3
d.
e. All the same
ANS: a
17. If a solute dissolves in a solvent, then
a. the polarity of the solute is similar to the polarity of the solvent.
b. the mixture forms a more ordered system (so the entropy decreases).
c. G  0 , for the process.
d. H  0 , for the process.
e. a and c
ANS: a
18. Which compound would exhibit the greatest solubility in hexane (C 6H14)?
NH4Cl
a.
CH3OH
b.
CH3CH2NH2
d.
KNO3
e.
CH 3
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CH 3 CH CH 2 CH 3
c.
ANS: c
19. Which of the following is (are) water-soluble (will not form two layers when mixed with water)?
a. CH3CH2OCH2CH3
b. CH3CHOHCH3
c. CH3CH2CH2CH2CH2OH
d. b and c
e. a, b, and c
ANS: b
Chapter 2
20. Which compound would exhibit the greatest water solubility?
a. CH3CH2CH2CH2CH2OH
b. CH3CH2CH2CH2OH
c. CH3CH2CH2CH2Cl
d. CH3CH2CH2Cl
e. All the same
ANS: b
21. The chemical reactivity of a molecule depends mostly on its
a. functional groups.
b. molar mass.
c. carbon skeleton.
d. physical properties.
e. concentration.
ANS: a
22. A molecule having the structural feature below is classified as a(n)
O
||
R
O
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O
R
a. ester
b. acid anhydride
c. ketone
d. carboxylic acid
e. aldehyde
ANS: b
23. Which structure represents an aldehyde?
H
O
O
b.
CO2 H
d.
e. All of the above
O
O
a.
c.
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20
Organic Compounds: A First Look
ANS: c
Chapter 2
24. Which structure represents a nitrile?
CH3CH2NH2
a.
CH3CH2C —
—N
b.
O
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CH 3 CH 2 CNH 2
c.
CH3C — CCH3
b.
O
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CH 3 CH 2 CH 2 CH
c.
CH3CH2OCH3
d.
e. None of the above
ANS: b
25. Which structure represents an alkyne?
CH3CH2CH=CH2
a.
O
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CH 3 COCH 2 CH 3
d.
CH3CH2CH2CH2CH3
e.
ANS: b
26. Which structure does not contain the functional group indicated?
O
ketone
CH3CH2OH alcohol
a.
CH3CH2NH2 amine
b.
O
NH 2
amide
aldehyde
H
O
d.
ANS: c
e.
O
c.
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22
Organic Compounds: A First Look
Short Answer
27. Why is PO43– stable, whereas NO43– is not? Show structures and explain.
O
||
O — P — O
|
O
ANS:
-
-
O
||
O — N — O
|
O
-
-
The Lewis structure for PO43– is reasonable with the formal charges shown. The phosphorus atom, being a
third row element, can expand its valence number of electrons. The Lewis structure for NO 43– is also
reasonable with the formal charges shown, but the nitrogen atom is too small to expand its valence.
28. Explain and illustrate why I3– exists, but F3– does not.
ANS: 0
–1
0
I — I — I
The central I atom can expand its valence number of electrons. The analogous structure involving F is not
reasonable because F cannot expand its valence number of electrons. Therefore, F bonds to just one other
atom.
29. Draw five possible structural isomers for C4H7C1. (Do not show identical structures.)
Cl
ANS:
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Chapter 2
30. Draw a reasonable structure for C6H8NO2Br.
O
||
N+
ANS:
O–
Br
Or any other structure that fits the formula and the degree of unsaturation = 3
31. Draw the four structural isomers with the formula C3H6C12.
Cl
ANS:
Cl
Cl
Cl
Cl
Cl
Cl
Cl
32. a) Calculate the degree of unsaturation (DU) of C9H13N.
ANS: (2n + 2 + 1 – 13) / 2 = (20 + 1 – 13) / 2 = 4
b) Draw a structure with the formula C9H13N.
ANS:
NH 2
Many other isomers of this compound are possible.
33. Give the functional group of each molecule.
—
—O
CH3CH2CH2OH
a.
H
||
O
d.
ANS: a. alcohol
b. carboxylic acid
c. ketone
d. aldehyde
CH3CH2CO2H
b.
H
N
—
—O
c.
O
||
O
e.
f.
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24
Organic Compounds: A First Look
e. amide
f. ester
Chapter 2
25
34. Draw shorthand representations of each:
CH3CH2C —
— CCH2OH
a.
H
|
C
H
H2 C
H2 C
O
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H
— CH 2
CH — O — C — C —
C
H2
c.
CHO
C
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C
H3 C
O
H
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H3 C — C ————— OH
|
CH 3
b.
H2
C
C
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C
C
|
H
d.
H
ANS:
OH
OH
a.
||
O
b.
O
||
O
c.
O
H
d.
35. Diethyl ether (CH3CH2OCH2CH3) and 1-butanol (CH3CH2CH2CH2OH) have similar solubility in water,
but 1-butanol has a much higher boiling point (118°) than diethyl ether (35°). Explain.
ANS: Both diethyl ether and 1-butanol form hydrogen bonds with water (which furnishes the O–H). 1Butanol can hydrogen bond with other 1-butanol molecules, but diethyl ether cannot hydrogen bond with
other diethyl ether molecules.
36. Neopentane C(CH3)4 has a melting point of –17° and an atmospheric boiling point of 10°. The isomeric
pentane CH3CH2CH2CH2CH3 has a lower melting point of –130° and a higher boiling point of 36°. Explain.
ANS: Neopentane is very symmetrical and packs together well in a crystal, therefore giving a relatively high
melting point, but the London forces of pentane are stronger since those molecules have more surface area
to contact each other.
26
Organic Compounds: A First Look
Chapter 2
27
37. Using bond dissociation energies, predict which compound is more stable and explain:
HOCH 2 CH 2 C —
—N
O
||
H2 C —
— CHCNH
A
2
B
Table 2.1 Average Bond Dissociation Energies (in kcal/mol).
C — H 98
C — C 81
C — F 116
C—
— C 145
N — H 92
C — N 66
C — Cl 79
C — C 198
O — H 109
C — O 79
C — Br 66
C—
— O 173
C—
— N 204
C — I 52
ANS:
C—H4=
O—H
C—O
392
109
79
C—H3=
N—H2=
—C
C—
294
184
145
C—C2=
C—
—N
162
C—
—O
173
204
C—C
81
946
C—N
66
943
A is just slightly more stable since its bonds are predicted to take more energy to break apart. Actually the
stability of the compounds is very similar.
38. Draw and name the constitutional isomers of C2H6O.
ANS:
OH
ethanol
O
dimethyl ether