National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
Release 19April 2018
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
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
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+ nitric oxide O-protonated
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 monosulfide CS HCS+ Thioformyl cation
Phosphorus monoxide PO HPO+ HPO cation
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
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 isocyanide HNC H2CN+ hydrocyanonium cation
hydrogen isocyanide HNC CNH2+ CNH2+
hydrogen isocyanide HNC HCNH+ HCNH+
Hydrogen cyanide HCN H2CN+ hydrocyanonium cation
Hydrogen cyanide HCN CNH2+ CNH2+
Hydrogen cyanide HCN HCNH+ HCNH+
aluminum dihydride AlH2 AlH3+ aluminum trihydride cation
Formyl radical HCO H2CO+ formaldehyde cation
Dinitrogen monohydride NNH N2H2+ trans-diazine cation
silicon dihydride SiH2 SiH3+ Silyl cation
Phosphino radical PH2 PH3+ Phosphine cation
Hydroperoxy radical HO2 H2O2+ Hydrogen peroxide cation
Hydrogen sulfide H2S H3S+ Sulfonium 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
Ozone O3 O3H+ protonated ozone
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
Methyl radical CH3 CH4+ Methane cation
Ammonia NH3 NH4+ ammonium cation
vinylidene CCH2 C2H3+ vinyl cation
Acetylene C2H2 C2H3+ vinyl cation
Formaldehyde H2CO CH3O+ Methoxy cation
Formaldehyde H2CO CH2OH+ hydroxymethyl cation
hydroxycarbene HOCH CH3O+ Methoxy cation
hydroxycarbene HOCH CH2OH+ hydroxymethyl cation
Silyl radical SiH3 SiH4+ Silane cation
Phosphine PH3 PH4+ phosphonium cation
Hydrogen peroxide H2O2 H3O2+ hydrogen peroxide, protonated
ketenyl radical HCCO CH2CO+ Ketene cation
formate neutral radical HCOO H2COO+ dioxymethyl cation
Hydrocarboxyl radical HOCO H2COO+ dioxymethyl cation
Thioformaldehyde H2CS H2CSH+ Thioformaldehyde, protonated
Nitrogen trifluoride NF3 NF3H+ protonated nitrogen trifluoride
Arsenic trifluoride AsF3 AsF3H+ Arsenic trifluoride, protonated
vinyl C2H3 C2H4+ Ethylene cation
Methanimine CH2NH CH2NH2+ methyleneamine cation
Methoxy radical CH3O CH3OH+ Methyl alcohol cation
Hydroxymethyl radical CH2OH CH3OH+ Methyl alcohol cation
diiminomethane HNCNH NCNH3+ Cyanamide, protonated
diiminomethane HNCNH HNCNH2+ diiminomethane, protonated
diazirine CH2NN NCNH3+ Cyanamide, protonated
diazirine CH2NN HNCNH2+ diiminomethane, protonated
diazomethane CH2NN NCNH3+ Cyanamide, protonated
diazomethane CH2NN HNCNH2+ diiminomethane, protonated
cyanamide NH2CN NCNH3+ Cyanamide, protonated
cyanamide NH2CN HNCNH2+ diiminomethane, protonated
Ketene CH2CO CH3CO+ acetyl cation
Oxirene C2H2O CH3CO+ acetyl cation
ethynol HCCOH CH3CO+ acetyl cation
dioxymethyl 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
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
hydroxymethylimine HOCHNH H2CONH2+ protonated formamide
formamide CHONH2 H2CONH2+ protonated formamide
formaldoxime CH2NOH H2CONH2+ protonated formamide
nitrosomethane CH3NO H2CONH2+ protonated formamide
1,2-oxaziridine CNOH3 H2CONH2+ protonated formamide
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
Ethylene oxide C2H4O CH3CHOH+ acetaldehyde, protonated
Ethylene oxide C2H4O C2H4OH+ ethylene oxide, protonated
Acetaldehyde CH3CHO CH3CHOH+ acetaldehyde, protonated
Acetaldehyde CH3CHO 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
aminoethene CH2CHNH2 C2H5NH+ Protonated Aziridine
aminoethene CH2CHNH2 C2H6N+ aziridine, protonated
Aziridine C2H5N C2H5NH+ Protonated Aziridine
Aziridine C2H5N 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 C3H7+ Isopropyl cation
Cyclopropane C3H6 C3H7+ cyclopropane, protonated
Propene CH2CHCH3 C3H7+ Isopropyl cation
Propene CH2CHCH3 C3H7+ cyclopropane, protonated
Guanidine CH5N3 CH6N3+ guanidinium
2-Chloroethanol CH2ClCH2OH CH2ClCH2OH2+ 2-chloroethanol, protonated
Ethylamine CH3CH2NH2 (CH3)2NH2+ dimethylammonium cation
Ethylamine CH3CH2NH2 CH3CH2NH3+ ethylamine, protonated
Dimethylamine CH3NHCH3 (CH3)2NH2+ dimethylammonium cation
Dimethylamine CH3NHCH3 CH3CH2NH3+ ethylamine, protonated
Propanal CH3CH2CHO CH3COHCH3+ acetone, protonated
2-Propen-1-ol C3H6O CH3COHCH3+ acetone, protonated
Acetone CH3COCH3 CH3COHCH3+ acetone, protonated
Propylene oxide C3H6O CH3COHCH3+ acetone, protonated
Oxetane C3H6O CH3COHCH3+ acetone, protonated
Cyclopropanol C3H5OH CH3COHCH3+ acetone, protonated
Acetone enol C3H6O 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
Propellane C5H6 C6H7+ benzene, protonated
phenyl C6H5 C6H6+ Benzene cation
Pyridine C5H5N C5H6N+ Pyridinium
Bicyclo[1.1.0]butane-1-carbonitrile C5H5N C5H6N+ Pyridinium
1,2,4,5-Hexatetraene C6H6 C6H7+ benzene, protonated
Fulvene C6H6 C6H7+ benzene, protonated
Benzene C6H6 C6H7+ benzene, protonated
2,4-Hexadiyne C6H6 C6H7+ benzene, protonated
Benzvalene C6H6 C6H7+ benzene, protonated
Hexa-1,5-diene-3-yne C6H6 C6H7+ benzene, protonated
Trimethylenecycopropane C6H6 C6H7+ benzene, protonated
1-Propanamine NH2CH2CH2CH3 C3H7NH3+ n-propylamine, protonated
1-Propanamine NH2CH2CH2CH3 (CH3)3NH+ protonated trimethyl amine
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
2-Propanamine, 2-methyl- C(CH3)3NH2 NC4H12+ tetramethyl ammonium cation
1-Propanamine, 2-methyl- C(NH2)H2C(CH3)HCH3 NC4H12+ tetramethyl ammonium cation
1-Butanamine C(NH2)H2CH2CH2CH3 NC4H12+ tetramethyl ammonium cation
diethylamine NH(C2H5)2 NC4H12+ tetramethyl ammonium cation
2-Butanamine CH3C(NH2)HCH2CH3 NC4H12+ tetramethyl ammonium cation