TOPIC: 2. Acids / Bases
SUBTOPIC: 21. Structure and Acidity
1. Which acid has the smallest pKa value?
A. HC≡CH
B. NH3
C. H2O
D. CH2=CH2
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2. Rank the following compounds in order of acidity (1 = most acidic).
CH3CH2OH
CH3CH2NH2
CH3C CH
CH3CH=CH2
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3. Which is the most basic compound? Which is the least basic?
A. NaOH
B. NaOOCCH3
C. NaOCH3
D. NaNH2
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4. Which is the most acidic compound? Which is the least acidic?
O
A.
O
O
O
O
OEt
OEt
EtO
O
B.
C.
D.
O
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5. Guanidine (structure shown below) is one of the stronger neutral nitrogen bases. Its
protonated form has a pKa of 13.6. (a) Write the structure of a neutral carbon acid that
guanidine would deprotonate.
NH
H2N
NH2
(b) Two different products of protonation are possible for guanidine. Write each and
using resonance structures, show which protonation product is more stable.
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6. Which is the most basic aniline and which is the least basic aniline?
NH2
NH2
A.
NH2
NH2
C.
B.
NO2
D.
Cl
OCH3
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7. Which is the most acidic and which is the least acidic phenol?
OH
OH
A.
NO2
B.
C.
CH2CH3
OH
OH
D.
NO2
NHCH3
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8. Which is the most basic compound and which is the least basic compound?
For extra credit, write the approximate pKa of the conjugate acid under each base.
CH3Li
LiOH
LiOOCH
LiNHCH3
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9. Which is the most acidic compound and which is the least acidic compound?
For extra credit, write the approximate pKa under each acid.
OH
O
OH
CH2OH
NH3+
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10. Which is the strongest carbon acid and which is the weakest carbon acid?
For extra credit, write the approximate pKa under each acid.
O
O
O
O
O
O
O
O
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11. Rank in order of basicity ( 1 = most basic ).
O
O
NH
NH
NH
NH
HN
NH
O
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12. Which is the weakest acid?
O
A. HBr
B. CH3CH2OH
C.
O
N
+ OH
O
D. CH3
C
OH
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13. Which is the strongest base that can exist in liquid NH3?
A. ─OH
B. ─NH2
C. ─CH3
D. NH3
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14. Which is the strongest base?
A. CH3CH2─
B. NH2─
C. CH3O─
D. HC≡C─
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15. Which amine would you expect to be more basic aniline or cyclohexylamine? Briefly
explain why?
NH2
NH2
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16. Which is more acidic phenol or p-nitrophenol? Explain using resonance structures.
OH
OH
NO2
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17. Which is the strongest acid?
O
A. HC CH
C. H2O
B. NH3
D. CH3
C
OH
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18. Which is the strongest base?
A. NaOH
B. KSH
C. CH3Li
D. NaNH2
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19. Which is the strongest acid?
A. CH3CH2OCH2CH3
B. CH3CH2OH
C. CH3CF2OH
D. CH2CH2NH2
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20. Which compound is not a Lewis acid?
A. BH3
B. CH3SSCH3
C. + C(CH3)3
D. AlCl3
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21. Which is the strongest base?
A. K O
CH3
B.
Li
N
C. CH3CH2MgBr
D. NaOH
CH3 CH3
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22. Which is the strongest carbon acid and which is the weakest carbon acid?
O
O
O
A.
O
O
C.
B.
EtO
O
O
O
D.
O
OEt
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23. Which is the most basic compound.and which is the least basic compound?
O
NH2
NH2
NH2
NH2
C.
B.
A.
D. Br
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24. Which is the most acidic phenol and which is the least acidic phenol?
OH
OH
OH
OH
NO2
A.
NO2
C.
B.
NO2
NO2
NO2
NO2
D.
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25. Which is the strongest acid?
O
A. CH3COH
O
B. CH2COH
NH3
OH
NH3+
C.
D.
+
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26. Which acid has the highest pKa?
O
OH
C. CH3O
Br
O
OH
OH
B.
A.
O
O
OH
D.
CH3
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27. Which acid has the lowest pKa?
O
OH
A.
D. O N
2
C. CH O
3
Br
OH
OH
OH
B.
O
O
O
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28. Draw the most important resonance structure of p-aminophenol that explains why paminophenol is a stronger base than aniline.
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29. Which is the strongest base that can exist in acetic acid?
O
A.
OH
B.
O
C. H2O
D. NH3
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30. Rank the following groups in accordance of the Cahn-Ingold-Prelog priority rules.
O
CH3C
CH3CH2O
HC C
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31. Which is the strongest acid?
A.
CH3CH3
B. CH2=CH2
C.
HC CH
D.
NH3
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32. Acetic acid (pKa = 4.8) and ethanol (pKa = 16) have very different acid strengths.
The major species present when acetic acid and ethanol are added to water and the pH is
adjusted to 7.0 are (identify two):
A. CH3CO2H
B. CH3CO2
C. CH3CH2OH
D. CH3CH2O
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33. Acetic acid is a stronger acid than ethanol. Explain using resonance structures.
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34. Which is the strongest acid?
A. CH3CH3
B. CH2=CH2
C. HC CH
D. NH3
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