Advices For Studying Organic Chemistry

Increasing base strength

Cl− CH 3 CO 2 − HO−
Very weak base Strong base
pKa of conjugate pKa of conjugate pKa of conjugate
acid (HCl) = −7 acid (CH 3 CO 2 H) = −4.75 acid (H 2 O) = −15.7

3. Amines are weak bases:

+ H O H −O H

Acid

H

Conjugate base

HN+ +

H

Base

NH 3

H

Conjugate acid

pKa = 9. (^2)

• H O H −O H
  Acid
  H
  Conjugate base
  H 3 CN+ +
  H
  Base
  CH 3 NH 2
  H
  Conjugate acid
  pKa = 10.6

1. The conjugate acids of ammonia and methylamine are the ammonium ion, NH 4 +
   (pKa = 9.2) and the methylammonium ion, CH 3 NH 3 + (pKa = 10.6) respectively.
   Since methylammonium ion is a weaker acid than ammonium ion, methylamine
   is a stronger base than ammonia.

3.6 PREDICTING THE OUTCOME OF ACID-BASE REACTIONS

3.6A General order of acidity and basicity:

1. Acid-base reactions always favor the formation of the weaker acid and the
   weaker base.

1. Equilibrium control: the outcome of an acid-base reaction is determined by the
   position of an equilibrium.