3. Acids and Bases

For each of the following compounds, indicate the atom that is protonated when an acid is added to a solution of the compound.

a.

b.

Rank the carbanions shown in the margin from most basic to least basic.

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b. How does the presence of an electronegative substituent such as Cl affect the acidity of a carboxylic acid?

c. How does the location of the substituent affect the acidity of the carboxylic acid?

Explain the relative acidities.

CH₂═CHCH₂OH, CH₃CH₂CH₂OH, HC≡CCH₂OH

Using the table of pK_a values given in [Appendix I] , answer the following:

d. Which is more electronegative: an sp³ oxygen or an sp² oxygen?

e. Which compounds demonstrate that the relative electronegativities of a hybridized nitrogen atom are sp > sp² > sp³?

Imidazole has two potentially basic sites (a and b). Of the two, where would you expect a proton to add preferentially?

Rationalize the rather large difference in pK_a values for the two carboxylic acids shown.

Rank the following amines in order of their basicity (strongest base = 1 ; weakest base = 6).

Using qualitative reasoning for the acid–base reactions shown,

(i) which is stronger, the acid or the conjugate acid?

(ii) Which side of the reaction is favored?

(iii) Would you expect a K_eq greater than, equal to, or less than 1?

(a)

Using qualitative reasoning for the acid–base reactions shown,

(i) which is stronger, the base or the conjugate base?

(ii) Which side of the reaction is favored?

(iii) Would you expect a K_eq greater than or less than 1?

(a)

Identify the most stable conjugate base in each pair. Tell which structural features you analyzed and why you weighted them as you did in picking one answer.

(c)

Identify the most stable conjugate base in each pair. Tell which structural features you analyzed and why you weighted them as you did in picking one answer.

(e)

Identify the most acidic proton in each pair. Tell which structural features you analyzed and why you weighted them as you did in picking one answer. [Always start by drawing the conjugate base.]

(a)

Identify the most acidic proton in each pair. Tell which structural features you analyzed and why you weighted them as you did in picking one answer. [Always start by drawing the conjugate base.]

(h)

Which anion in each pair would you expect to react more quickly with H⁺?

(a)