This page has acidity tables for heteroatom organic acids and carbon acids. |
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Because of the very large range of acid strengths ( greater than 1040 ), a logarithmic scale of acidity ( pKa ) is normally employed. Stronger acids have smaller or more negative pKa values than do weaker acids. A discussion of acid-base terminology is available here. The pKa values given here are extrapolated for water at 25 ºC. Many of the pKa values given for weak carbon acids are estimated from the rates of hydrogen exchange with very strong bases.
Common Name |
Formula |
Acidity Constant |
pKa |
trifluoromethanesulfonic acid |
CF3SO3H |
ca. 1013 |
ca. -13 |
benzenesulfonic acid |
C6H5SO3H |
ca. 103 |
ca. -2.5 |
methanesulfonic acid |
CH3SO3H |
ca. 3 * 102 |
ca. -2.0 |
trifluoroacetic acid |
CF3CO2H |
1.0 |
0.0 |
picric acid |
(O2N)3C6H2OH |
0.5 |
0.3 |
squaric acid |
K1 = 0.33 |
1.5 |
|
trichloroacetic acid |
CCl3CO2H |
0.23 |
0.77 |
oxalic acid |
(CO2H)2 |
K1 = 6.5 * 10-2
|
1.2 |
dichloroacetic acid |
CHCl2CO2H |
5.5 * 10-2 |
1.25 |
fluoroacetic acid |
FCH2CO2H |
2.5 * 10-3 |
2.6 |
chloroacetic acid |
ClCH2CO2H |
1.36 * 10-3 |
2.87 |
citric acid |
C(OH)(CH2CO2H)2CO2H |
K1 = 7.4 * 10-4
|
3.13 |
formic acid |
HCO2H |
1.77 * 10-4 |
3.75 |
ascorbic acid |
K1 = 6.7 * 10-5
|
4.17 |
|
benzoic acid |
C6H5CO2H |
6.3 * 10-5 |
4.20 |
acetic acid |
CH3CO2H |
1.77 * 10-5 |
4.75 |
thiophenol |
C6H5SH |
2.5 * 10-7 |
6.6 |
tropolone |
2.0 * 10-7 |
6.7 |
|
p-nitrophenol |
O2NC6H4OH |
5.7 * 10-8 |
7.2 |
peracetic acid |
CH3COO2H |
5.7 * 10-9 |
8.2 |
succinimide |
(CH2CO)2NH |
2.5 * 10-10 |
9.6 |
phenol |
C6H5OH |
10-10 |
10.0 |
chloral hydrate |
CCl3CH(OH)2 |
10-10 |
10.0 |
benzenesulfonamide |
C6H5SO2NH2 |
8 * 10-11 |
10.1 |
2-hydroxy-2-cyclohexenone |
5.0 * 10-11 |
10.3 |
|
ethanethiol |
C2H5SH |
2.5 * 10-11 |
10.6 |
acetoxime |
(CH3)2C=NOH |
6 * 10-13 |
12.2 |
2,2,2-trifluoroethanol |
CF3CH2OH |
4 * 10-13 |
12.4 |
imidazole |
C3H3N2H |
3.3 * 10-15 |
14.5 |
pyrrole |
C4H4NH |
10-15 |
15 |
ethanol |
C2H5OH |
10-16 |
16 |
1°-amides |
RCONH2 |
10-17 |
17 |
p-nitroaniline |
O2NC6H4NH2 |
3.3 * 10-19 |
18.5 |
t-butanol |
(CH3)3COH |
10-19 |
19 |
aniline |
C6H5NH2 |
10-27 |
27 |
1,1,1,3,3,3,-hexamethyldisilazane |
[(CH3)3Si]2NH |
10-30 |
30 |
pyrrolidine |
C4H8NH |
10-32 |
32 |
diisopropylamine |
[(CH3)2CH]2NH |
1.9 * 10-36 |
35.7 |
tetramethylpiperidine |
10-37 |
37 |
Michigan State University |
Common Name |
Formula |
Acidity Constant |
pKa |
tricyanomethane |
CH(CN)3 |
105 |
-5 |
dinitromethane |
CH2(NO2)2 |
2.5 * 10-4 |
3.6 |
5,5-dimethyl-1,3-cyclohexadione |
1.6 * 10-5 |
4.8 |
|
malonaldehyde |
CH2(CHO)2 |
10-5 |
5.0 |
Meldrum's acid |
8 * 10-6 |
5.1 |
|
2,4-pentanedione |
CH2(COCH3)2 |
1.26 * 10-9 |
8.9 |
hydrocyanic acid |
HCN |
6.3 * 10-10 |
9.2 |
nitromethane |
CH3NO2 |
6.3 * 10-11 |
10.2 |
malononitrile |
CH2(CN)2 |
10-11 |
11.0 |
ethyl acetoacetate |
CH3COCH2CO2C2H5 |
10-11 |
11.0 |
tris(trifluoromethyl)methane |
(CF3)3CH |
10-11 |
11.0 |
bis(methylsulfonyl)methane |
CH2(SO2CH3)2 |
2.0 * 10-13 |
12.7 |
diethyl malonate |
CH2(CO2C2H5)2 |
3.2 * 10-14 |
13.5 |
bromoform |
Br3CH |
3 * 10-14 |
13.7 |
chloroform |
Cl3CH |
3.2 * 10-16 |
15,5 |
cyclopentadiene |
10-16 |
16.0 |
|
aldehydes |
RCH2CHO |
10-17 |
17 |
cyclohexanone |
10-17 |
17 |
|
phenylacetylene |
C6H5C≡CH |
10-19 |
19.0 |
indene |
10-20 |
20 |
|
methyl ketones |
RCOCH3 |
10-20 |
20 |
tris(phenylthio)methane |
(C6H5S)3CH |
10-23 |
23 |
methylsulfones |
RSO2CH3 |
10-25 |
25 |
alkyl esters |
RCH2CO2C2H5 |
10-25 |
25 |
nitriles |
RCH2CN |
10-25 |
25 |
acetylene |
HC≡CH |
10-25 |
25 |
fluroform |
F3CH |
10-28 |
28 |
methylsulfoxides |
RSOCH3 |
10-30 |
30 |
1,3-dithiane |
(CH2)3S2CH2 |
10-31 |
31 |
triphenylmethane |
(C6H5)3CH |
3.2 * 10-32 |
31.5 |
diphenylmethane |
(C6H5)2CH2 |
3.2 * 10-34 |
33.5 |
1-methylnaphthylene |
1-C10H7CH3 |
10-37 |
37 |
2-methylnaphthylene |
2-C10H7CH3 |
3.2 * 10-38 |
37.5 |
toluene |
C6H5CH3 |
10-40 |
40 |
benzene |
C6H6 |
10-43 |
43 |
ethene |
C2H4 |
10-44 |
44 |
cyclopropane |
C3H6 |
10-46 |
46 |
ethane |
C2H6 |
10-48 |
48 |
Michigan State University |