pKa Values INDEX - Organic Chemistry Data

1 PKa Data Compiled by R. WilliamspKa ValuesINDEXI norganic2 Phenazine24 Phosphates3 Pyridine25 Carboxylic acids4, 8 Pyrazine26 Aliphatic4, 8 Aromatic7, 8 Quinoline27 Phenols9 Quinazoline27 Alcohols and oxygen acids10, 11 Quinoxaline27 Amino Acids12 Special Nitrogen Compounds28 Peptides13 Hydroxylamines28 Nitrogen Compounds14 Hydrazines28 Aliphatic amines15, 17, 19 Semicarbazones28 Cyanoamines16 Amidoximes28 Anilines17, 18, 20 Thiols29 Nucleosides21 Carbon Acids30,31 Special Table Heterocycles22 Indicators31 Acridine23 References32-34 Benzoquinoline24 Cinnoline23 Hydantoin24 Imidazole24 For complex chelating agents, see also reference This document was compiled by Jencks and has been added to by WestheimerProvided by the ACS, Organic Division Updated 4/7/2022 Page 1pKa Data Compiled by R. , *28H2PO4 * *77Al(OH) (OH) * , , *77H2 AsO4 *77H3 P2O7 *77 HAsO4* *77H2P2O7= *77As2O304HP2O7= * * * , , * (OH) , , , , , *28, , (70%) * * , *, , * *HSe * * *2, 30HS * *, * , , , , 78Ge(OH) , , (OH) , , , , * * * * * * *, * , , + , , (see above!)

2 H2N2O2 * *97H3O+97* Indicates a thermodynamic (OH)20* ( )4 (78)Provided by the ACS, Organic Division Updated 4/7/2022 Page 2 PHOSPHATES AND , , + , ( OOCCH2)2NH+CH2 --, , , , acid 2-phosphate , , , , , ( OOCCH22NH+(CH2)2- --, , , , + , , , , +(CH2) , , (CH2)3---, , (CH2) , , (CH2)5CH(COO )---, , , , +(CH2)4) , acid , , acid +(CH2) , acid , +(CH2)10---, , OOC(CH2)10---, , (CH3) , , , , , (C6H5) , , , acidsinosinic , strong, strong, , , , , (a), , (a), , , , , , , , , , phosphate( ), , , , , , (CH2)4PO3H2 <2, , , , (CH2)3PO3H2 <2, , , , (CH3)PO3H2 <2, , , , <2, , , , , , (a), , , , , **These Values were obtained in 50% , (a) The compounds were not sufficiently , graphical plots of a large number of substitutedphosphorus compounds see , ,1 , , , , , (CH2)5CH(COOH)- 1, --57 Provided by the ACS, Organic Division Updated 4/7/2022 Page , acids, substitutedPhosphonates (Ref.)

3 2) *20X-H-H-NH3+-NH3+ *20X(CH2) (CH3)3N+ *20X(CH2) (CH3)2NH+ *20X(CH2) + *20X(CH2)5PO3 + *20X(CH2) *20X(CH2) *20 Phosphines in acetonitrile, see ref. *20 CARBOXYLIC * , (enol) , , , , ( ) (2) , , * * , * -keto- -methyl valeric * , , (trans-enol) +(cis-enol) , *20 Tartaric + , *20+ or , * , * * * * * *20 (C6H5) * * *20* Indicates thermodynamic by the ACS, Organic Division Updated 4/7/2022 Page 4 Unsaturated acids (25 ) * *2cis-CH3-CH= *2H-CH= * * *2trans-C6H5-CH= *2C6H5CH=CHCO2H** * * *2C6H5CH=CHCO2H** *2m-ClC6H4CH=CHCO2H** * *2 Unsaturated acids, Cis- and Trans-C CR2HR1CO2HC * * * * * * ** **22,4,6-(CH3)3C6H2- ** ** ** **2 Dicarboxylic acids, unsaturated* , Dicarboxylic acidsCitraconic (Dimethylmaleic acid) , (1,1-dimethylcyclopropane-23-dicarboxyli c *, * , , , *, * , *, * , , *, * , , (Dimethylfumaric acid)** , **in 40% , *thermodynamicItaconic (1-Propene-2-3-dicarboxylic acid) , , by the ACS, Organic Division Updated 4/7/2022 Page 5 AliphaticAlicyclic Dicarboxylic acidsCompoundpKRefCompoundpKRef1, , , , , , ,3-trans -Cyclobutanedi-1, , , ,2-trans-Cyyclopentane-1, , , ,3-trans-Cyclopentane-1, , , ,2-trans-Cyclohexane-1,3 , , ,3-trans-Cyclohexane-1,4-cis-Cyclohexane , , , , acids* , , , O-O , , (high melting) , O-O , , (low melting) , ,O , , (high melting) , ,O , , (low melting) , , , , , , , , , , , , , , , , :2-Dichlorosuccinic , , , , ----20B, , :2-Dibromosuccinic , , , , ----20meso-1.

4 2-Dimethylsuccinic , , *All are thermodynamic [ ]octane-1-carboxylic acids, acid, , , --2 , by the ACS, Organic Division Updated 4/7/2022 Page 6 Lysergic , * * * , * * * , --2(CH3) * , --2(CH3)3N+ , * *isolysergic , * * , * * * * *Hydroxycyclohexanecarboxylic * * *Cyclohexanecarboxylic (CH3) * *cis-1, * * *cis-1, * * *cis-1, *trans-1, *trans-1, *trans-1, (CH3) * *2 (CH3) ** benzoic acids (ref. 2)COOH*thermodynamicfor complex chelating agents, see also ref. also page 9a for more carboxylic acidompOrtho-substituted benzoic * *Benzoic * * ** * *2,6-(CH3) ,3,4,6-(CH3) ,3,5,6-(CH3) * * * * * * * * * ** * * *2,4,6-(CH3) * *2,3,4,5-(CH3) Polycarboxylic acidsRef. 2 AcidPosition of *Phthalic1, * *Isophthalic1, * *Terephthalic1, * *Hemimellitic1,2, * * *Trimellitic1,2, * * *Provided by the ACS, Organic Division Updated 4/7/2022 Page 7 Trimesic1,3, * * *Mellophanic1,2,3, * * * *Prehnitic1,2,3, * * * *Pyromellitic1,2,4, * * * *Benzenepentacarboxylic1,2,3,4, * * * * * ,3,4,5, * * * * * **ionic strength , ** , acid* , , AcidsRef.

5 77N-2-sulfoethyliminodiacetic , , acid* , -Bromobutyric , (carbamoylmethyl)-imino-diacetic , , , , , , -diaminopropionic , , , , , (carboxymethyl)-aminomethyl , , , , , , , , , * , , , * , , -iodopropionic* , , * , , , , , , , , , *ThermodynamicProvided by the ACS, Organic Division Updated 4/7/2022 Page , , (30o)50o-Methoxyphenol--, , , ,5 dimethyl-2-Aminophenolphenol , ,5-dihydroxybenzene-1,3 disulphonic * * * * *(CH3)3N+ ** * * * * * * * * * * * * * * * * * * * * * ** * Thermodynamic**Reference 52 Provided by the ACS, Organic Division Updated 4/7/2022 Page 9 ALCOHOLS and other OXYGEN CH(C2F5) OH , (C3F7)2CH , (OH) in H2SO4 HC1O4 HNO3refCF3CH2(CH3) ,4, .82 . **634,4 (C3F7) ** (CH2OH)) * ( )97. 64 **CH3CH2OH1664 **Substituent effects for ionization of , , ,3 ,3 -Trimethyl-Unsubstituted triphenyl-methanol-4,4;,4;-Trichloro-4-N itro-CCl3CH2OH CF3CH2 OHHydroxamic (extrap)( ) (CH3) alcohols=R CH2 OH alcohols in 50% oxygen (50% dioxane)CHF2 (CF2) (CH2) CHMe CHMe CH(CF3) dioxane**50 aquaeous ethanolProvided by the ACS, Organic Division Updated 4/7/2022 Page 10646464 OTHER OXYGEN ACIDSH ydroxamic , , >1167 -Naphtho-~ 1-oxide (INAA) ,2,3-cyclohexanetrione-1, 1-oxide perchlorate>1167 Isonitrosoacetone (INA) (SA) ,2,3-Cyclohexanetrionetrioxime ,2, toluene-p-sulphonate>11674-Benzyloxypyri dine acids2-Methoxypyridine , ,4-(CH) , ROOH (Ref.

6 70) 93 Pyridine-2-aldoxime , by the ACS, Organic Division Updated 4/7/2022 Page 114-Pyridine-1, ethyl ester 13, acid (glucamicacid) acidsref. , acid -Aminobutyric , (?) , , , -Aminobutyric >12, , , , (?) < , , , ethyl ester , by the ACS, Organic Division Updated 4/7/2022 Page (L,L) Ala (L) or (D) Gly (L) or (D) Ala Ala (LL) Ala Ala (LD) Ala OH (DD) Ala OH (LD) Ala Ala Ala OH (3L) Ala Ala Ala OH (LLD) Ala-Ala-Ala OH (LDL) Ala-Ala-Ala OH (DLL) OH (3D) Ala-Ala-Ala-Ala OH (4L) Ala-Ala-Ala-Ala OH (LLDL) Ala-Ala-Ala-Ala OH (LDLL) Ala-Ala-Ala-Ala OH (DLLL) Lys-Ala OH (LL) Lys-Ala OH (LD) Ala-Lys-Ala OH (3L) Ala-Lys-Ala OH (LDL) Ala-Lys-Ala OH (LLD) Ala-Lys-Ala-Ala OH (4L) Ala-Lys-Ala OH (LDLL) Ala-Lys-Ala-Ala-Ala OH (5L) Ala-Lys-Ala-Ala-Ala OH (LDLLL) Lys-Lys OH (LL) Lys-Lys OH (LD) Lys-Lys OH (3L) Lys-Lys-Lys OH (LDL) Lys-Lys-Lys OH (LDD) , , , , oxidized , , , (LL) (LD) (LL) (LD) (LL) (DL) by the ACS, Organic Division Updated 4/7/2022 Page 13 Lysyllysine (LD) COMPOUNDSA liphatic -Alanine -Amino-n-butyric acid ester , , 77 Glycine *?

7 XXNH3+XCH2NH3+X(CH2)2NH3+X(CH2)3NH3+X(CH 2)4NH3+X(CH2)5NH3+ * * * * * * * * * * * * * * * * * * * *2H2C= * * * * * *2X-H-NH3+-CO2 -SO3 -PO3 2X-NH3+ * (CH2)2NH3+ (CH2)2NH3+ (CH2)4NH3+ (CH2)5NH3+ (CH2)8NH3+ (CH2)10NH3+ (CH2)3NH3+ -(p-Tolyl) -(p-Tolyl) ,O-dimethylhydroxylamine + *thermodynamic by the ACS, Organic Division Updated 4/7/2022 Page 14 Aliphatic AminesMethyl- -diethylamino-ethyl-sulfide1, ,2-Dimethyl- , 2-pyrroline ,2-Imino-2-methylpropane 2-pyrroline , 2-pyrroline , ,2-Dimethyl- AminesN-Ethyl derivative of: 1, , , ,6-dimethyl-piperidine , aminescis-2, , (6) (CH2) (CH2) (CH2) (CH3) (CH2) (CH2CN) (CH2CN) (CH2CH2CN) (CH2CH2CN) (CH2CH2CN) (CH2) (CH3) (CH2) (CH2)2CN by the ACS, Organic Division Updated 4/7/2022 Page 15 , " complex chelating agents of aliphatic amines,see also ref. (3,4-dihydroxyphenyl) (CH3) amines and imines (in 80% methyl cellosolve) (ref. 2) , , " , , * * *Provided by the ACS, Organic Division Updated 4/7/2022 Page 16(CH3)3N+ (CH3) * (CH3) * * * , * * * * * * * *(CH3) + * * *, * * * * * *(CH3) * * * * * * * * * (in 50% ethanol)Substituent XC6H4N(CH3)2ref.

8 , (CH3) (CH3) , , (CH3) , (CH3) (CH3) by the ACS, Organic Division Updated 4/7/2022 Page 17 Ortho-substituted anilines (in 50% ethanol) , *2,3-(CH3) *2,4-(CH3) *2,5-(CH3) , *2,6-(CH3) , ,5-(CH3) * *2-(CH3) (CH3) ,6-(CH3)2-4-(CH3) ,4-(CH3)2-6-(CH3) ,6-(CH3) ,4,6-[(CH3)3C3]-< * * * * * anilines*RC6H5 NHRC6H5N(CH3)R ~ *ThermodynamicProvided by the ACS, Organic Division Updated 4/7/2022 Page 18 AMINESref. 77 Secondary aminesN-Butylaminoacetic , aminesN,N' , ,2' , ,N'-di-n-propylethylenediamine , , ,N'-diacetic acid , ,3-diaminobutane, , , ,3-diaminobutane, , , ,2'-diaminodiethyl , -carboxymethylaminopropionic acid1,3-diamino-2,2-dimethylpropane , , ,N'-Di-(2-aminoethyl) , , , ,N' , , , , , , , , ,N' , , ,N-diacetic acid , amines2-(2-hydroxypropylamino) , (2-aminoethyl) , (2-hydroxyethyl)aminoacetic (3-hydroxypropylamino) , , , , -amino- , , acid , , , ,2, , , (hydroxymethyl) 12-amino-2'-hydroxydiethyl sulfide (carbamoylmethyl)-iminodiacetic , ,2' , , ,3-diamino-2, , ,3' , , ,2-Di-(2-aminoethylthio) , , , , , , , , , (2-hydroxyethyl) , , , , , , , by the ACS, Organic Division Updated 4/7/2022 Page 19 Ref.

9 5 Methyl-[ -diethylamino-ethyl] , , , , , (3) , (4) (6) (Ref. 88)m-Substituted (CH3) (CH3) ,5-(CH3) ,5-[C(CH3)3] , ,5-(OCH3) , (reference 88)substituted , , , , , , , , , , , , , , ,Provided by the ACS, Organic Division Updated 4/7/2022 Page 20 Anilines (in 50% ethanol)5' , , , deoxyriboside 5' ( ), " , ' , , , " , ' , * ' , , , , , (deoxy) , 6mesoGMP (2' + 3') , , , '-GMP (deoxy) , , , , , , hydrochloride " , , , , , , , , , , ( )382-Amino-4,5-dimethylphenol , , ,N-Dimethyl-2,4-dinitroaniline , ' , , to , , , ' , , , , " , ' , , , ' , , , , ( ), , , , , , , (2' + 3') , , (deoxy) , ' , , , , , (deoxy) , " , , , " , , ' , , , , , , 6 Provided by the ACS, Organic Division Updated 4/7/2022 Page 21 Heterocyclic Bases (Ref. 2)NNNNNNNNNNNNNNNNNNNNNNNNNP yridine *pK (20 )2354678 Quinoline *Isoquinoline *Benzoquinoline *23456789101 Acridine , *7, *Phenanthridine ,3-Benzacridine ,4-Benzacridine *1,2-Benzacridine *Pyrimidine *Pyrazine *Cinnoline *Phthalazine *Quinazoline *Quinoxaline *a 50% , , , (acridone)--f, , , 739 Acridine1--2--3--4--5--9--Ref.

10 2 Provided by the ACS, Organic Division Updated 4/7/2022 Page * * * * * * *> (1-CH3--) ,9-(CH3) 50% ethanol; ref. 398-amino-1, , ' , ,7-benzoquinoline , '-amino-5,6-benzoquinoline , '-amino-5,6-benzoquinoline , ,8,benzoquinoline7, , , , , , , ' , , , ' , ' ( )a191' ',4' , , , , ', (decomp.) , , , , , , :7:8:9-tetrahydro- ,o' , ,5, , , , , by the ACS, Organic Division Updated 4/7/2022 Page (NH2 ) (1,2) (OH ) , (2,3) , , , , , , , , , , , , , , ,2' , , , , , , ,10-Diamino-3,8-Dimethyl- , , , , (phenanthridone) < , , , ,7, , , , -239 PyridinesPicolimic , , , ,4,6-Trihydroxy-4,6, , 13 (2',4'-Dihydroxyphenyl) (N-Methylacetamido) (N-Methylbenzamido) (NH2 )3-(N-Methylacetamod) (N-Methylbenzamido) (N-Methylacetamido) by the ACS, Organic Division Updated 4/7/2022 Page 244-(N-Methylbenzamido) (CH3) , , , ,4, , , 13, acetylimine benzylimine , , , , N-oxides (see oxygen acids)Substituted (CH3) by the ACS, Organic Division Updated 4/7/2022 Page 25 Ortho-Substituted Pyridines (in 50% ethanol) , ,6-Dihydroxy-5,67, , 13 (CH3) , ,6-[(CH3)2CH] (CH3) , (CH3) ,6-[(CH3)3C]2 complex chelating agents, see also ref.