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Experimental Proton Affinities

Proton affinities in kJ mol-1
Molecule name State Conformation Proton Affinity Uncertainity Product molecule Product name reference commment
H- Hydrogen atom anion 2S Kh 1675.3   H2 Hydrogen diatomic webbook
H Hydrogen atom 1S Kh 257.7   H2+ Hydrogen cation webbook derived from webbook
He Helium atom 1S Kh 177.8   HeH+ Helium hydride cation webbook
N Nitrogen atom 4S Kh 342.2   NH+ imidogen cation webbook
O Oxygen atom 3S Kh 485.2   OH+ hydoxyl cation webbook
F- Fluorine atom anion 1S Kh 1555.0 5.0 HF Hydrogen fluoride webbook
F Fluorine atom 2P Kh 340.1   HF+ hydrogen fluoride cation webbook
Ne Neon atom 1S Kh 198.8   NeH+ neon hydrogen cation webbook
Mg Magnesium atom 1S Kh 819.6   MgH+ magnesium monohydride cation webbook
Si Silicon atom 3P Kh 837.0   SiH+ silicon monohydride cation webbook
P Phosphorus atom 4S Kh 626.8   PH+ phosphorus monohydride cation webbook
S Sulfur atom 3P Kh 664.3   HS+ sulfur monohydride cation webbook
Cl- Chlorine atom anion 1S Kh 1394.9   HCl Hydrogen chloride webbook
Cl Chlorine atom 2P Kh 513.6   HCl+ hydrogen chloride cation webbook
Ar Argon atom 1S Kh 369.2   ArH+ Argon hydride cation webbook
Sc Scandium atom 2D Kh 914.0   ScH+ Scandium monohydride cation webbook
Cr Chromium atom 7S Kh 791.3   CrH+ protonated chromium webbook
Br- Bromine atom anion 1S Kh 1353.7 0.2 HBr hydrogen bromide webbook
Br Bromine atom 2P Kh 554.4   HBr+ hydrogen bromide cation webbook
I- Iodine atom anion 1S Kh 1315.2 0.1 HI Hydrogen iodide webbook
H2 Hydrogen diatomic 1Σg D∞h 422.3   H3+ hydrogen trimer cation webbook
CN- cyanide anion 1Σ C∞v 1466.5 0.7 HCN Hydrogen cyanide webbook
N2 Nitrogen diatomic 1Σg D∞h 493.8   NNH+ Dinitrogen monohydride cation webbook
OH- hydroxide anion 1Σ C∞v 1633.1 0.0 H2O Water webbook
CO Carbon monoxide 1Σ C∞v 594.0   HCO+ Formyl cation webbook
CO Carbon monoxide 1Σ C∞v 426.3   COH+ Carbon Monoxide, protonated webbook
NO Nitric oxide 2Π C∞v 531.8   HNO+ Nitrosyl hydride cation webbook
O2 Oxygen diatomic 3Σg D∞h 421.0   HO2+ Hydroperoxy cation webbook
HF Hydrogen fluoride 1Σ C∞v 484.0   H2F+ dihydrogen fluoride cation webbook
PO Phosphorus monoxide 2Π C∞v 682.0   HPO+ HPO cation webbook
HS- mercapto anion 1Σ C∞v 1470.0 3.0 H2S Hydrogen sulfide webbook
CS carbon monosulfide 1Σ C∞v 791.5   HCS+ Thioformyl cation webbook
HCl Hydrogen chloride 1Σ C∞v 556.9   H2Cl+ dihydrogen monochloride cation webbook
HSe- selenium monohydride anion 1Σ C∞v 1428.8 2.9 H2Se Hydrogen selenide webbook
HBr hydrogen bromide 1Σ C∞v 584.2   H2Br+ protonated hydrogen bromide webbook
H2O Water 1A1 C2v 691.0   H3O+ hydronium cation webbook
HCO Formyl radical 2A' Cs 636.0   H2CO+ formaldehyde cation webbook
CO2 Carbon dioxide 1Σg D∞h 540.5   HOCO+ Hydrocarboxyl cation webbook
N2O Nitrous oxide 1Σ C∞v 575.2   NNOH+ Nitrous Oxide, O-protonated webbook O-protonated
N2O Nitrous oxide 1Σ C∞v 549.8   HNNO+ Nitrous oxide, N-protonated webbook N-protonated
NO2 Nitrogen dioxide 2A1 C2v 591.0   HNO2+ nitrous acid cation webbook
H2S Hydrogen sulfide 1A1 C2v 705.0   H3S+ Sulfonium cation webbook
C2H2 Acetylene 1Σg D∞h 641.4   C2H3+ vinyl cation webbook
NH3 Ammonia 1A1 C3v 853.6   NH4+ ammonium cation webbook
H2CO Formaldehyde 1A1 C2v 712.9   CH2OH+ hydroxymethyl cation webbook
H2O2 Hydrogen peroxide 1A C2 674.5   H3O2+ hydrogen peroxide, protonated webbook
HCO2- formate anion 1A1 C2v 1449.0 5.0 HCOOH Formic acid webbook
NO3- nitrate anion 1A1' D3h 1357.7 0.8 HNO3 Nitric acid webbook
NF3 Nitrogen trifluoride 1A1 C3v 568.4   NF3H+ protonated nitrogen trifluoride webbook
PH3 Phosphine 1A1 C3v 785.0   PH4+ phosphonium cation webbook
H2CS Thioformaldehyde 1A1 C2v 759.7   H2CSH+ Thioformaldehyde, protonated webbook
C2H3- vinyl anion 1A' Cs 1704.0 9.0 C2H4 Ethylene webbook
CH2NH Methanimine 1A' Cs 852.9   CH2NH2+ methyleneamine cation webbook
CH3O- methoxy anion 1A1 C3v 1598.0 8.0 CH3OH Methyl alcohol webbook
CH2CO Ketene 1A1 C2v 825.3   CH3CO+ acetyl cation webbook
HCOOH Formic acid 1A' Cs 742.0   CH3OO+ methylperoxy cation webbook
C2H4 Ethylene 1Ag D2h 680.5   C2H5+ Ethyl cation webbook
N2H4 Hydrazine 1A C2 853.2   N2H5+ protonated hydrazine webbook
CH3OH Methyl alcohol 1A' Cs 754.3   CH3OH2+ Methanol, protonated webbook
HSO4- bisulfate anion 1A' Cs 1295.0 11.0 H2SO4 Sulfuric acid webbook
C2H5- Ethyl anion 1A' Cs 1758.0 8.4 C2H6 Ethane webbook
C3H4 cyclopropene 1A1 C2v 818.5   C3H5+ Allyl cation webbook
CH2CCH2 allene 1A1 D2d 775.3   C3H5+ Allyl cation webbook
CH3CCH propyne 1A' C3v 748.0   C3H5+ Allyl cation webbook
CH3NH2 methyl amine 1A' Cs 899.0   CH3NH3+ protonated methylamine webbook
CH3N3 methyl azide 1A' Cs 833.0   CH3NHN2+ methyl azide, protonated webbook
CH3CHO Acetaldehyde 1A' Cs 768.5   CH3CHOH+ acetaldehyde, protonated webbook
CH3COO- acetate anion 1A' eclipsed 1457.0 5.9 CH3COOH Acetic acid webbook
CF3COO- trifluoro acetate anion 1A' Cs 1355.0 12.0 CF3COOH trifluoroacetic acid webbook
CH3PH2 Methyl phosphine 1A' Cs 851.5   CH3PH3+ methyl phosphine, protonated webbook
NH2CONH2 Urea 1A C2 868.4 2.5 H2NCOHNH2+ urea, protonated webbook
CH2ClCH2OH 2-Chloroethanol 1A' Cs 766.1   CH2ClCH2OH2+ 2-chloroethanol, protonated webbook
C3H6 Cyclopropane 1A1' D3h 750.3   C3H7+ Isopropyl cation webbook
CH2CHCH3 Propene 1A' Cs 751.6   C3H7+ Isopropyl cation webbook
CH3CH2NH2 Ethylamine 1A' Cs 912.0   CH3CH2NH3+ ethylamine, protonated webbook
CH3NHCH3 Dimethylamine 1A' Cs 929.5   (CH3)2NH2+ dimethylammonium cation webbook
C4H5N Pyrrole 1A1 C2v 875.4   C4H6N+ pyrrole, protonated webbook
C5H5N Pyridine 1A1 C2v 930.0   C5H6N+ Pyridinium webbook
N(CH3)3 Trimethylamine 1A1 C3v 948.9   C3H7NH3+ n-propylamine, protonated webbook
NH2CH2CH2CH3 1-Propanamine 1A' Cs 917.8   C3H7NH3+ n-propylamine, protonated webbook

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