National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
Release 22May 2022
NIST Standard Reference Database 101
IIExperimental data
IIICalculated data
IVData comparisons
VCost comparisons
VIInput and output files
VIITutorials and Units
VIIILinks to other sites
XOlder CCCBDB versions
XIII Vibrations
XIVReaction data
XVEntropy data
XVIBibliographic data
XVIIIon data
XVIIIBad calculations
XIXIndex of properties
XXH-bond dimers

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Proton Affinity

Click on formula for calculated relative enthalpies.
Name Species   Species Name
Hydrogen atom H H2+ Hydrogen cation
Helium atom He HeH+ Helium hydride cation
Lithium atom Li LiH+ lithium hydride cation
Beryllium atom Be BeH+ beryllium monohydride cation
Boron atom B BH+ boron monohydride cation
Carbon atom C CH+ Methylidyne cation
Nitrogen atom N NH+ imidogen cation
Oxygen atom O OH+ hydoxyl cation
Fluorine atom F HF+ hydrogen fluoride cation
Neon atom Ne NeH+ neon hydrogen cation
Sodium atom Na NaH+ sodium hydride cation
Magnesium atom Mg MgH+ magnesium monohydride cation
Aluminum atom Al AlH+ aluminum monohydride cation
Silicon atom Si SiH+ silicon monohydride cation
Phosphorus atom P PH+ phosphorus monohydride cation
Sulfur atom S HS+ sulfur monohydride cation
Chlorine atom Cl HCl+ hydrogen chloride cation
Argon atom Ar ArH+ Argon hydride cation
Potassium atom K KH+ Potassium hydrogen cation
Calcium atom Ca CaH+ Calcium monohydride cation
Scandium atom Sc ScH+ Scandium monohydride cation
Chromium atom Cr CrH+ Chromium hydride cation
Manganese atom Mn H+ Hydrogen atom cation
Manganese atom Mn XeH+ Xenon, protonated
Zinc atom Zn ZnH+ Zinc, protonated
Gallium atom Ga GaH+ Gallium monohydride cation
Germanium atom Ge GeH+ Germaniun monohyrdide cation
Arsenic atomic As AsH+ Arsenic monohydride cation
Selenium atom Se HSe+ selenium monohydride cation
Bromine atom Br HBr+ hydrogen bromide cation
Krypton atom Kr KrH+ Protonated Krypton
Tin atom Sn H+ Hydrogen atom cation
Tin atom Sn XeH+ Xenon, protonated
Antimony atom Sb H+ Hydrogen atom cation
Antimony atom Sb XeH+ Xenon, protonated
Tellurium atom Te H+ Hydrogen atom cation
Tellurium atom Te XeH+ Xenon, protonated
Iodine atom I HI+ Hydrogen iodide cation
Xenon atom Xe H+ Hydrogen atom cation
Xenon atom Xe XeH+ Xenon, protonated
Hydrogen diatomic H2 H3+ hydrogen trimer cation
beryllium monohydride BeH BeH2+ Beryllium dihydride cation
Boron monohydride BH BH2+ Boron dihydride cation
Methylidyne CH CH2+ methylene cation
Imidogen NH NH2+ Amino cation
Hydroxyl radical OH H2O+ water cation
Hydrogen fluoride HF H2F+ dihydrogen fluoride cation
Carbon diatomic C2 C2H+ Ethynyl cation
Cyano radical CN HCN+ hydrogen cyanide cation
Cyano radical CN HNC+ hydrogen isocyanide cation
aluminum monohydride AlH AlH2+ aluminum dihydride cation
Carbon monoxide CO HCO+ Formyl cation
Carbon monoxide CO COH+ Carbon Monoxide, protonated
Nitrogen diatomic N2 NNH+ Dinitrogen monohydride cation
Silylidyne SiH SiH2+ silicon dihydride cation
Nitric oxide NO HNO+ Nitrosyl hydride cation
Nitric oxide NO NOH+ O-protonated nitric oxide
phosphorus monohydride PH PH2+ Phosphino cation
Oxygen diatomic O2 HO2+ Hydroperoxy cation
Mercapto radical HS H2S+ Hydrogen sulfide cation
Hydrogen chloride HCl H2Cl+ dihydrogen monochloride cation
Fluorine diatomic F2 F2H+ Fluorine, protonated
Carbon monophosphide CP HCP+ Phosphaethyne cation
carbon monosulfide CS HCS+ Thioformyl cation
Phosphorus monoxide PO HPO+ Hydrogen phosphorus oxide cation
Sulfur monoxide SO HSO+ Sulfur Monoxide, S-protonated
Sulfur monoxide SO SOH+ Sulfur Monoxide, protonated
Monochlorine monoxide ClO HOCl+ hypochlorous acid cation
Chlorine monofluoride ClF ClFH+ Chlorine fluoride, F-protonated
Chlorine monofluoride ClF FClH+ Chlorine fluoride, Cl-protonated
Arsenic monohydride AsH AsH2+ Arsenic dihydride cation
Chlorine diatomic Cl2 Cl2H+ Chlorine, protonated
Selenium monohydride HSe H2Se+ Hydrogen selenide cation
hydrogen bromide HBr H2Br+ protonated hydrogen bromide
Bromine monoxide BrO HOBr+ Hypobromous acid cation
Phosphorus monoselenide PSe PH+ phosphorus monohydride cation
Antimony monohydride SbH H2+ Hydrogen cation
Telluryl radical TeH H2+ Hydrogen cation
Hydrogen iodide HI H2I+ Iodonium
Antimony nitride SbN NH+ imidogen cation
Antimony monofluoride SbF HF+ hydrogen fluoride cation
Tellurium monoxide TeO OH+ hydoxyl cation
Sodium Iodide NaI NaH+ sodium hydride cation
Antimony monochloride SbCl HCl+ hydrogen chloride cation
Tellurium diatomic Te2 H+ Hydrogen atom cation
Tellurium diatomic Te2 XeH+ Xenon, protonated
boron dihydride BH2 BH3+ boron trihydride cation
Methylene CH2 CH3+ methyl cation
Amino radical NH2 NH3+ ammonia cation
Water H2O H3O+ hydronium cation
Ethynyl radical C2H C2H2+ acetylene cation
Hydrogen cyanide HCN H2CN+ hydrocyanonium cation
Hydrogen cyanide HCN CNH2+ N-protonated hydrogen isocyanide
Hydrogen cyanide HCN HCNH+ N-protonated HCN
hydrogen isocyanide HNC H2CN+ hydrocyanonium cation
hydrogen isocyanide HNC CNH2+ N-protonated hydrogen isocyanide
hydrogen isocyanide HNC HCNH+ N-protonated HCN
aluminum dihydride AlH2 AlH3+ aluminum trihydride cation
Formyl radical HCO H2CO+ formaldehyde cation
Hydroxymethylidyne COH H2CO+ formaldehyde cation
Dinitrogen monohydride NNH N2H2+ trans-diazene cation
silicon dihydride SiH2 SiH3+ Silyl cation
Fluoromethylene HCF CH2F+ fluoromethyl cation
Phosphino radical PH2 PH3+ Phosphine cation
Hydroperoxy radical HO2 H2O2+ Hydrogen peroxide cation
Hydrogen sulfide H2S H3S+ Sulfonium cation
azide radical N3 HN3+ Hydrazoic acid cation
Carbon dioxide CO2 HOCO+ Hydrocarboxyl cation
Nitrous oxide N2O NNOH+ Nitrous Oxide, O-protonated
Nitrous oxide N2O HNNO+ Nitrous oxide, N-protonated
Thioformyl radical HCS H2CS+ thioformaldehyde cation
Carbonyl fluoride FCO HFCO+ formyl fluoride cation
Nitrogen dioxide NO2 HNO2+ nitrous acid cation
Chloromethylene HCCl CH2Cl+ chloromethyl cation
Difluoromethylene CF2 CHF2+ difluoromethyl cation
Ozone O3 O3H+ protonated ozone
Sulfur Hydroxide SOH H2CS+ thioformaldehyde cation
chlorofluoromethylene CFCl CHFCl+ Chlorofluoromethyl cation
Sulfur dioxide SO2 SO2H+ protonated sulfur dioxide
Thiosulfeno radical HS2 H2S2+ hydrogen disulfide cation
germylene GeH2 GeH3+ germyl cation
Arsenic dihydride AsH2 AsH3+ Arsine cation
Hydrogen selenide H2Se H3Se+ Hydrogen Selenide, protonated
Carbon disulfide CS2 CS2H+ Carbon disulfide, protonated
dichloromethylene CCl2 CHCl2+ dichloromethyl cation
Hydrogen Telluride H2Te H3+ hydrogen trimer cation
Tellurium Dioxide TeO2 HO2+ Hydroperoxy cation
Xenon difluoride XeF2 F2H+ Fluorine, protonated
Carbon sulfide Telluride SCTe HCS+ Thioformyl cation
Methyl radical CH3 CH4+ Methane cation
Ammonia NH3 NH4+ ammonium cation
vinylidene CCH2 C2H3+ vinyl cation
Acetylene C2H2 C2H3+ vinyl cation
Dihydrogen cyanide radical H2CN CH2NH+ Methanimine cation
Dihydrogen cyanide radical H2CN CHNH2+ Aminocarbene cation
Aminomethylidyne radical CNH2 CH2NH+ Methanimine cation
Aminomethylidyne radical CNH2 CHNH2+ Aminocarbene cation
methyleneazane HCNH CH2NH+ Methanimine cation
methyleneazane HCNH CHNH2+ Aminocarbene cation
hydroxycarbene HOCH CH3O+ Methoxy cation
hydroxycarbene HOCH CH2OH+ hydroxymethyl cation
Formaldehyde H2CO CH3O+ Methoxy cation
Formaldehyde H2CO CH2OH+ hydroxymethyl cation
Silyl radical SiH3 SiH4+ Silane cation
fluoromethyl radical CH2F CH3F+ methyl fluoride cation
nitroxide H2NO NH2OH+ Hydroxylamine cation
Phosphine PH3 PH4+ phosphonium cation
Hydrogen peroxide H2O2 H3O2+ hydrogen peroxide, protonated
water oxide H2OO H3O2+ hydrogen peroxide, protonated
ketenyl radical HCCO CH2CO+ Ketene cation
hydrogen azide HN3 NH2NN+ hydrazoic acid, protonated
hydrogen azide HN3 HNNNH+ 1,2-Triazadienium
formate neutral radical HCOO H2COO+ dioxymethyl cation
Hydrocarboxyl radical HOCO H2COO+ dioxymethyl cation
Thioformaldehyde H2CS H2CSH+ Thioformaldehyde, protonated
chloramine NH2Cl NH3Cl+ protonated monochloroammonia
Nitrogen trifluoride NF3 NF3H+ protonated nitrogen trifluoride
Arsine AsH3 AsH4+ Arsonium
chloromethyl radical CH2Cl CH3Cl+ Methyl chloride cation
Arsenic trifluoride AsF3 AsF3H+ Arsenic trifluoride, protonated
Tellurium trioxide TeO3 O3H+ protonated ozone
vinyl C2H3 C2H4+ Ethylene cation
Methanimine CH2NH CH2NH2+ methyleneamine cation
aminomethylene CHNH2 CH2NH2+ methyleneamine cation
Methoxy radical CH3O CH3OH+ Methyl alcohol cation
Hydroxymethyl radical CH2OH CH3OH+ Methyl alcohol cation
Silane SiH4 SiH5+ Silane, protonated
hydroxylamine NH2OH NH3OH+ N-protonated hydroxylamine
hydroxylamine NH2OH NH2OH2+ protonated hydroxylamine
Ammonia Oxide NH3O NH3OH+ N-protonated hydroxylamine
Ammonia Oxide NH3O NH2OH2+ protonated hydroxylamine
diazirine CH2N2 NCNH3+ Cyanamide, protonated
diazirine CH2N2 HNCNH2+ diiminomethane, protonated
diazirine CH2N2 NH3CN+ cyanamide, amine protonated
diazirine CH2N2 NH2CNH+ cyanamide, cn protonated
diiminomethane HNCNH NCNH3+ Cyanamide, protonated
diiminomethane HNCNH HNCNH2+ diiminomethane, protonated
diiminomethane HNCNH NH3CN+ cyanamide, amine protonated
diiminomethane HNCNH NH2CNH+ cyanamide, cn protonated
diazomethane CH2NN NCNH3+ Cyanamide, protonated
diazomethane CH2NN HNCNH2+ diiminomethane, protonated
diazomethane CH2NN NH3CN+ cyanamide, amine protonated
diazomethane CH2NN NH2CNH+ cyanamide, cn protonated
cyanamide NH2CN NCNH3+ Cyanamide, protonated
cyanamide NH2CN HNCNH2+ diiminomethane, protonated
cyanamide NH2CN NH3CN+ cyanamide, amine protonated
cyanamide NH2CN NH2CNH+ cyanamide, cn protonated
Oxirene C2H2O CH3CHO+ acetaldehyde cation
Oxirene C2H2O CH3CO+ acetyl cation
Oxirene C2H2O CH2COH+ ketene, protonated
Ketene CH2CO CH3CHO+ acetaldehyde cation
Ketene CH2CO CH3CO+ acetyl cation
Ketene CH2CO CH2COH+ ketene, protonated
ethynol HCCOH CH3CHO+ acetaldehyde cation
ethynol HCCOH CH3CO+ acetyl cation
ethynol HCCOH CH2COH+ ketene, protonated
Dioxymethyl radical H2COO CH3OO+ methylperoxy cation
Dioxirane CH2O2 CH3OO+ methylperoxy cation
Formic acid HCOOH CH3OO+ methylperoxy cation
thiomethoxy CH3S CH3SH+ Methanethiol cation
Methyl chloride CH3Cl CH3ClH+ methyl chloride, protonated
Nitric acid HNO3 H2NO3+ Nitric Acid, Protonated
tetraiodomethane CI4 CH+ Methylidyne cation
silicon tetraiodide SiI4 SiH+ silicon monohydride cation
methylmethylene CH3CH C2H5+ Ethyl cation
Ethylene C2H4 C2H5+ Ethyl cation
Methyl alcohol CH3OH CH3OH2+ Methanol, protonated
Hydrazine N2H4 N2H5+ protonated hydrazine
water dimer H2OH2O H5O2+ Dihydroxonium ion
Vinyloxy radical CH2CHO C2H4O+ ethylene oxide cation
Vinyloxy radical CH2CHO H2COCH2+ Methyl, (methyleneoxoniumyl)-
Acetyl radical CH3CO C2H4O+ ethylene oxide cation
Acetyl radical CH3CO H2COCH2+ Methyl, (methyleneoxoniumyl)-
1,2-oxaziridine CNOH3 H2CONH2+ protonated formamide
1,2-oxaziridine CNOH3 NH3CHO+ Formamide, N-Protonated
1,2-oxaziridine CNOH3 NH2CHOH+ Formamide, O-protonated
nitrosomethane CH3NO H2CONH2+ protonated formamide
nitrosomethane CH3NO NH3CHO+ Formamide, N-Protonated
nitrosomethane CH3NO NH2CHOH+ Formamide, O-protonated
formaldoxime CH2NOH H2CONH2+ protonated formamide
formaldoxime CH2NOH NH3CHO+ Formamide, N-Protonated
formaldoxime CH2NOH NH2CHOH+ Formamide, O-protonated
formamide CHONH2 H2CONH2+ protonated formamide
formamide CHONH2 NH3CHO+ Formamide, N-Protonated
formamide CHONH2 NH2CHOH+ Formamide, O-protonated
hydroxymethylimine HOCHNH H2CONH2+ protonated formamide
hydroxymethylimine HOCHNH NH3CHO+ Formamide, N-Protonated
hydroxymethylimine HOCHNH NH2CHOH+ Formamide, O-protonated
Methanethiol CH3SH CH3SH2+ protonated methylsulfide
Carbonic acid H2CO3 H3CO3+ carbonic acid, protonated
Ethyl radical C2H5 C2H6+ ethane cation
methyl amine CH3NH2 CH3NH3+ protonated methylamine
propyne CH3CCH C3H5+ Allyl cation
allene CH2CCH2 C3H5+ Allyl cation
cyclopropene C3H4 C3H5+ Allyl cation
ethenol CH2CHOH CH3CHOH+ acetaldehyde, protonated
ethenol CH2CHOH C2H4OH+ ethylene oxide, protonated
Acetaldehyde CH3CHO CH3CHOH+ acetaldehyde, protonated
Acetaldehyde CH3CHO C2H4OH+ ethylene oxide, protonated
Ethylene oxide C2H4O CH3CHOH+ acetaldehyde, protonated
Ethylene oxide C2H4O C2H4OH+ ethylene oxide, protonated
Methyl phosphine CH3PH2 CH3PH3+ methyl phosphine, protonated
methyl azide CH3N3 CH3NHN2+ methyl azide, protonated
Methyl nitrite CH3ONO NH3COOH+ protonated Carbamic acid
Methyl nitrite CH3ONO NH2COOH2+ Carbamic acid, O-protonated
Carbamic acid NH2COOH NH3COOH+ protonated Carbamic acid
Carbamic acid NH2COOH NH2COOH2+ Carbamic acid, O-protonated
Methane, nitro- CH3NO2 NH3COOH+ protonated Carbamic acid
Methane, nitro- CH3NO2 NH2COOH2+ Carbamic acid, O-protonated
Ethane C2H6 C2H7+ Ethane, protonated
Ammonia Dimer NH3NH3 N2H7+ ammonia ammonium dimer
Aziridine C2H5N C2H5NH+ Protonated Aziridine
Aziridine C2H5N C2H6N+ aziridine, protonated
aminoethene CH2CHNH2 C2H5NH+ Protonated Aziridine
aminoethene CH2CHNH2 C2H6N+ aziridine, protonated
N-methylmethanimine CH2NCH3 C2H5NH+ Protonated Aziridine
N-methylmethanimine CH2NCH3 C2H6N+ aziridine, protonated
ethanimine CH3CHNH C2H5NH+ Protonated Aziridine
ethanimine CH3CHNH C2H6N+ aziridine, protonated
Urea NH2CONH2 CH5N2O+ urea, N-protonated
Urea NH2CONH2 H2NCOHNH2+ urea, protonated
Cyclopropane C3H6 CH3CHCH3+ Isopropyl cation
Cyclopropane C3H6 C3H7+ cyclopropane, protonated
Propene CH2CHCH3 CH3CHCH3+ Isopropyl cation
Propene CH2CHCH3 C3H7+ cyclopropane, protonated
diaminomethane NH2CH2NH2 NH2CH2NH3+ diaminoethane, protonated
Guanidine CH5N3 CH6N3+ guanidinium
2-Chloroethanol CH2ClCH2OH CH2ClCH2OH2+ 2-chloroethanol, protonated
Dimethylamine CH3NHCH3 (CH3)2NH2+ dimethylammonium cation
Dimethylamine CH3NHCH3 CH3CH2NH3+ ethylamine, protonated
Ethylamine CH3CH2NH2 (CH3)2NH2+ dimethylammonium cation
Ethylamine CH3CH2NH2 CH3CH2NH3+ ethylamine, protonated
Acetone CH3COCH3 CH3COHCH3+ acetone, protonated
Propylene oxide C3H6O CH3COHCH3+ acetone, protonated
2-Propen-1-ol C3H6O CH3COHCH3+ acetone, protonated
Propanal CH3CH2CHO CH3COHCH3+ acetone, protonated
Oxetane C3H6O CH3COHCH3+ acetone, protonated
Acetone enol C3H6O CH3COHCH3+ acetone, protonated
Cyclopropanol C3H5OH CH3COHCH3+ acetone, protonated
3H-pyrrole C4H5N C4H6N+ pyrrole, protonated
3H-pyrrole C4H5N C4H6N+ pyrrole, beta-protonated
3H-pyrrole C4H5N C4H6N+ pyrrole, alpha-protonated
2H-pyrrole C4H5N C4H6N+ pyrrole, protonated
2H-pyrrole C4H5N C4H6N+ pyrrole, beta-protonated
2H-pyrrole C4H5N C4H6N+ pyrrole, alpha-protonated
Cyclopropanecarbonitrile C4H5N C4H6N+ pyrrole, protonated
Cyclopropanecarbonitrile C4H5N C4H6N+ pyrrole, beta-protonated
Cyclopropanecarbonitrile C4H5N C4H6N+ pyrrole, alpha-protonated
(Z)-2-Butenenitrile C4H5N C4H6N+ pyrrole, protonated
(Z)-2-Butenenitrile C4H5N C4H6N+ pyrrole, beta-protonated
(Z)-2-Butenenitrile C4H5N C4H6N+ pyrrole, alpha-protonated
(E)-2-Butenenitrile C4H5N C4H6N+ pyrrole, protonated
(E)-2-Butenenitrile C4H5N C4H6N+ pyrrole, beta-protonated
(E)-2-Butenenitrile C4H5N C4H6N+ pyrrole, alpha-protonated
Pyrrole C4H5N C4H6N+ pyrrole, protonated
Pyrrole C4H5N C4H6N+ pyrrole, beta-protonated
Pyrrole C4H5N C4H6N+ pyrrole, alpha-protonated
Allylcyanide CH2CHCH2CN C4H6N+ pyrrole, protonated
Allylcyanide CH2CHCH2CN C4H6N+ pyrrole, beta-protonated
Allylcyanide CH2CHCH2CN C4H6N+ pyrrole, alpha-protonated
Propellane C5H6 C6H7+ benzene, protonated
phenyl C6H5 C6H6+ Benzene cation
E-2,4-pentadienenitrile C5H5N C5H6N+ Pyridinium
Pyridine C5H5N C5H6N+ Pyridinium
Bicyclo[1.1.0]butane-1-carbonitrile C5H5N C5H6N+ Pyridinium
1-Propanol C3H7OH C3H9O+ trimethyl oxonium cation
Isopropyl alcohol CH3CHOHCH3 C3H9O+ trimethyl oxonium cation
Ethane, methoxy- CH3OC2H5 C3H9O+ trimethyl oxonium cation
Fulvene C6H6 C6H7+ benzene, protonated
Prismane C6H6 C6H7+ benzene, protonated
Benzvalene C6H6 C6H7+ benzene, protonated
Hexa-1,5-diene-3-yne C6H6 C6H7+ benzene, protonated
2,4-Hexadiyne C6H6 C6H7+ benzene, protonated
Dewar Benzene C6H6 C6H7+ benzene, protonated
3,4-Dimethylenecyclobutene C6H6 C6H7+ benzene, protonated
Benzene C6H6 C6H7+ benzene, protonated
1,2,4,5-Hexatetraene C6H6 C6H7+ benzene, protonated
Trimethylenecycopropane C6H6 C6H7+ benzene, protonated
2-Propanamine CH3CH(NH2)CH3 C3H7NH3+ n-propylamine, protonated
2-Propanamine CH3CH(NH2)CH3 (CH3)3NH+ protonated trimethyl amine
Trimethylamine N(CH3)3 C3H7NH3+ n-propylamine, protonated
Trimethylamine N(CH3)3 (CH3)3NH+ protonated trimethyl amine
1-Propanamine NH2CH2CH2CH3 C3H7NH3+ n-propylamine, protonated
1-Propanamine NH2CH2CH2CH3 (CH3)3NH+ protonated trimethyl amine
1-Butanamine C(NH2)H2CH2CH2CH3 NC4H12+ tetramethyl ammonium cation
diethylamine NH(C2H5)2 NC4H12+ tetramethyl ammonium cation
2-Propanamine, 2-methyl- C(CH3)3NH2 NC4H12+ tetramethyl ammonium cation
1-Propanamine, 2-methyl- C(NH2)H2C(CH3)HCH3 NC4H12+ tetramethyl ammonium cation
2-Butanamine CH3C(NH2)HCH2CH3 NC4H12+ tetramethyl ammonium cation