Advices For Studying Organic Chemistry

Table 3.1 Relative Strength of Selected Acids and their Conjugate Bases

Acid Approximate pKa Conjugate Base

Strongest Acid HSbF 6 (a super acid) < − 12 SbF 6 − Weakest Base

Incr

easing ac

id stre

ngth

HI

H 2 SO 4

HBr

HCl

C 6 H 5 SO 3 H

(CH 3 ) 2 O+H

(CH 3 ) 2 C=O+H

CH 3 O+H 2

H 3 O+

HNO 3

CF 3 CO 2 H

HF

H 2 CO 3

CH 3 CO 2 H

CH 3 COCH 2 COCH 3

NH 4 +

C 6 H 5 OH

HCO 3 −

CH 3 NH 3 +

H 2 O

CH 3 CH 2 OH

(CH 3 ) 3 COH

CH 3 COCH 3

HC≡CH

H 2

NH 3

CH 2 =CH 2

− 10

− 9

− 9

− 7

−6.5

−3.8

−2.9

−2.5

−1.74

−1.4

0.18

3.2

3.7

4.75

9.0

9.2

9.9

10.2

10.6

15.74

16

18

19.2

25

35

38

44

I−

HSO 4 −

Br−

Cl−

C 6 H 5 SO 3 −

(CH 3 ) 2 O

(CH 3 ) 2 C=O

CH 3 OH

H 3 O

HNO 3 −

CF 3 CO 2 −

F−

HCO 3 −

CH 3 CO 2 −

CH 3 COCH−COCH 3

NH 4 +

C 6 H 5 O−

HCO 32 −

CH 3 NH 3

HO−

CH 3 CH 2 O−

(CH− 3 ) 3 CO−

CH 2 COCH 3

HC≡C−

H−

NH 2 −

CH 2 =CH−

Incre

asing base strength

Weakest Acid CH 3 CH 3 50 CH 3 CH 2 − Strongest Base

3.5C PREDICTING THE STRENGTH OF BASES

1. The stronger the acid, the weaker will be its conjugate base.


2. The larger the pKa of the conjugate acid, the stronger is the base.