124
ACIDS AND BASES
Table 4.5 pK a values of CH–CO, CH–CN, and CH–NO 2 acids
Acid
Conjugate base
pK a
CH 3 CO 2 CH 2
CH 3 CO 2 CH 3
24
CH 3 COCH 3
CH 3 COCH 2
19
CH 3 CH=O
CH 2 CH=O
1 7
CH 2
CH 3 O 2 C
CH 3 O 2 C
C
CH 3 O 2 C
CH 3 O 2 C
H
13
CH 3 COCH 2 CO 2 CH 3
CH 3 COCHCO 2 CH 3
11
CH 3 COCH 2 COCH 3
CH 3 COCHCOCH 3
9
H 3 C–C≡N
H 2 C–C≡N
2 5
CH 3 NO 2
CH 2 NO 2
10
Table 4.6 pK a values of N
+ , O
+ , and S
+ acids
Acid
Conjugate base
pK a
C NH
H 2 N
H 2
2
N
C NH
H 2 N
H 2 N
13.6
CH 3 NH 3
CH 3 NH 2
10.6
(CH 3 ) 2 NH 2
(CH 3 ) 2 NH
10.7
(CH 3 ) 3 NH
(CH 3 ) 3 N
9 . 8
NH 4
NH 3
9.2
N
H
N
5.2
Ph–NH(CH 3 ) 2
Ph–N(CH 3 ) 2
5.1
Ph–NH 3
Ph–NH 2
4.6
Ph 2 NH 2
Ph 2 NH
0.8
H 3 C–C≡NH
H 3 C–C≡N
−10
H 3 C C
NH 2
OH
CH 3 CONH 2
−1.4
(continues)
Table 4.6 (continued)
H 3 O
H 2 O
−1.7
Ph C
NH 2
OH
PhCONH 2
−2.2
CH 3 OH 2
CH 3 OH
−2.2
CH 3 CH 2 OH 2
CH 3 CH 2 OH
−2.4
(CH 3 ) 3 C–OH 2
(CH 3 ) 3 C–OH
−3.8
O H
H 3 C
H 3 C
O
H 3 C
H 3 C
−3.8
H 3 C C
OH
OH
H 3 C C
OH
O
−6.1
H 3 C C
OCH 3
OH
H 3 C C
OCH 3
O
−6.5
Ph–OH 2
Ph–OH
−6.7
PhCH=OH
PhCH=O
−7
(CH 3 ) 2 C=OH
(CH 3 ) 2 C=O
−7.2
CH 3 CH=OH
CH 3 CH=O
−8
S H
H 3 C
H 3 C
S
H 3 C
H 3 C
−5.4
CH 3 SH 2
CH 3 SH
−6.8
according to its functional group, and we hope that
this will also emphasize similarities and differences
in related structures. It also means that you may find
some examples turning up in more than one table.
As we consider different aspects of chemical reactivity in subsequent chapters, we shall see how pK a