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).

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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?

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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.

(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?

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7. Which is the most acidic and which is the least acidic phenol?

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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.

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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.

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11. Rank in order of basicity ( 1 = most basic ).

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12. Which is the weakest acid?

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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?

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16. Which is more acidic phenol or p-nitrophenol? Explain using resonance structures.

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17. Which is the strongest acid?

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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?

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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?

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22. Which is the strongest carbon acid and which is the weakest carbon acid?

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23. Which is the most basic compound.and which is the least basic compound?

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24. Which is the most acidic phenol and which is the least acidic phenol?

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25. Which is the strongest acid?

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26. Which acid has the highest pKa?

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27. Which acid has the lowest pKa?

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