Isocyanic acid


Reaction thermochemistry data

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled by: John E. Bartmess

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Individual Reactions

CNO- + Hydrogen cation = Isocyanic acid

By formula: CNO- + H+ = CHNO

Quantity Value Units Method Reference Comment
Δr341.18 ± 0.61kcal/molD-EABradforth, Kim, et al., 1993gas phase; D-EA cycle requires a DH ca 4 kcal/mol weaker
Δr344.7 ± 2.1kcal/molG+TSWight and Beauchamp, 1980gas phase
Quantity Value Units Method Reference Comment
Δr334.74 ± 0.71kcal/molH-TSBradforth, Kim, et al., 1993gas phase; D-EA cycle requires a DH ca 4 kcal/mol weaker
Δr338.3 ± 2.0kcal/molIMREWight and Beauchamp, 1980gas phase

(CAS Reg. No. 1140500-24-8 • 4294967295Isocyanic acid) + Isocyanic acid = CAS Reg. No. 1140500-24-8

By formula: (CAS Reg. No. 1140500-24-8 • 4294967295CHNO) + CHNO = CAS Reg. No. 1140500-24-8

Quantity Value Units Method Reference Comment
Δr43.1 ± 3.0kcal/molN/ATaft, 1987gas phase; value altered from reference due to change in acidity scale

(CAS Reg. No. 67131-48-0 • 4294967295Isocyanic acid) + Isocyanic acid = CAS Reg. No. 67131-48-0

By formula: (CAS Reg. No. 67131-48-0 • 4294967295CHNO) + CHNO = CAS Reg. No. 67131-48-0

Quantity Value Units Method Reference Comment
Δr58.1 ± 2.2kcal/molN/ATaft, 1987gas phase; value altered from reference due to change in acidity scale

Gas phase ion energetics data

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data evaluated as indicated in comments:
HL - Edward P. Hunter and Sharon G. Lias
L - Sharon G. Lias

Data compiled as indicated in comments:
B - John E. Bartmess
LL - Sharon G. Lias and Joel F. Liebman
LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron

Quantity Value Units Method Reference Comment
IE (evaluated)11.595 ± 0.005eVN/AN/AL
Quantity Value Units Method Reference Comment
Proton affinity (review)180.kcal/molN/AHunter and Lias, 1998HL
Quantity Value Units Method Reference Comment
Gas basicity171.8kcal/molN/AHunter and Lias, 1998HL

Ionization energy determinations

IE (eV) Method Reference Comment
11.595 ± 0.005PIRuscic and Berkowitz, 1994LL
11.62 ± 0.02PECradock, Ebsworth, et al., 1972LLK
11.60 ± 0.01PERowland, Eland, et al., 1968RDSH

Appearance energy determinations

Ion AE (eV) Other Products MethodReferenceComment
CHO+15.52NEICompernolle, 1975LLK
CHO+15.76 ± 0.15NEIBogan and Hand, 1971LLK
CNO+≤16.532HPIRuscic and Berkowitz, 1994LL
CNO+16.66 ± 0.15HEIBogan and Hand, 1971LLK
CNO+≤16.1HEIRowland, Eland, et al., 1968RDSH
NH+17.26 ± 0.15COEIBogan and Hand, 1971LLK
NH+≤17.7COEIRowland, Eland, et al., 1968RDSH
NO+15.76 ± 0.15?EIBogan and Hand, 1971LLK

De-protonation reactions

CNO- + Hydrogen cation = Isocyanic acid

By formula: CNO- + H+ = CHNO

Quantity Value Units Method Reference Comment
Δr341.18 ± 0.61kcal/molD-EABradforth, Kim, et al., 1993gas phase; D-EA cycle requires a DH ca 4 kcal/mol weaker; B
Δr344.7 ± 2.1kcal/molG+TSWight and Beauchamp, 1980gas phase; B
Quantity Value Units Method Reference Comment
Δr334.74 ± 0.71kcal/molH-TSBradforth, Kim, et al., 1993gas phase; D-EA cycle requires a DH ca 4 kcal/mol weaker; B
Δr338.3 ± 2.0kcal/molIMREWight and Beauchamp, 1980gas phase; B

References

Go To: Top, Reaction thermochemistry data, Gas phase ion energetics data, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Bradforth, Kim, et al., 1993
Bradforth, S.E.; Kim, E.H.; Arnold, D.W.; Neumark, D.M., Photoelectron Spectroscopy of CN-, NCO-, and NCS-, J. Chem. Phys., 1993, 98, 2, 800, https://doi.org/10.1063/1.464244 . [all data]

Wight and Beauchamp, 1980
Wight, C.A.; Beauchamp, J.L., Acidity, basicity, and ion/molecule reactions of isocyanic acid in the gas phase by ICR spectroscopy, J. Phys. Chem., 1980, 84, 2503. [all data]

Taft, 1987
Taft, R.W., The Nature and Analysis of Substitutent Electronic Effects, Personal communication. See also Prog. Phys. Org. Chem., 1987, 16, 1. [all data]

Hunter and Lias, 1998
Hunter, E.P.; Lias, S.G., Evaluated Gas Phase Basicities and Proton Affinities of Molecules: An Update, J. Phys. Chem. Ref. Data, 1998, 27, 3, 413-656, https://doi.org/10.1063/1.556018 . [all data]

Ruscic and Berkowitz, 1994
Ruscic, B.; Berkowitz, J., The H-NCO bond energy and Hf(NCO) from photoionization mass spectrometric studies of HNCO and NCO, J. Chem. Phys., 1994, 100, 4498. [all data]

Cradock, Ebsworth, et al., 1972
Cradock, S.; Ebsworth, E.A.V.; Murdoch, J.D., Photoelectron spectra of some Group 4 pseudohalides and related compounds, J. Chem. Soc. Faraday Trans. 2, 1972, 68, 86. [all data]

Rowland, Eland, et al., 1968
Rowland, C.G.; Eland, J.H.D.; Danby, C.J., A spin-forbidden predissociation in the mass spectrum of isocyanic acid, Chem. Commun., 1968, 1535. [all data]

Compernolle, 1975
Compernolle, F., Mass spectrum and heat of formation of isocyanic acid. Production of [HCO]+ from discrete electronic state of molecular ion, Org. Mass Spectrom., 1975, 10, 289. [all data]

Bogan and Hand, 1971
Bogan, D.J.; Hand, C.W., Mass spectrum of isocyanic acid, J. Phys. Chem., 1971, 75, 1532. [all data]


Notes

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