Isocyanic acid


Gas phase 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 as indicated in comments:
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein

Quantity Value Units Method Reference Comment
Δfgas-24.300kcal/molReviewChase, 1998Data last reviewed in December, 1970
Δfgas-23.1 ± 3.2kcal/molIonOkabe, 1970ALS
Quantity Value Units Method Reference Comment
gas,1 bar56.936cal/mol*KReviewChase, 1998Data last reviewed in December, 1970

Gas Phase Heat Capacity (Shomate Equation)

Cp° = A + B*t + C*t2 + D*t3 + E/t2
H° − H°298.15= A*t + B*t2/2 + C*t3/3 + D*t4/4 − E/t + F − H
S° = A*ln(t) + B*t + C*t2/2 + D*t3/3 − E/(2*t2) + G
    Cp = heat capacity (cal/mol*K)
    H° = standard enthalpy (kcal/mol)
    S° = standard entropy (cal/mol*K)
    t = temperature (K) / 1000.

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Temperature (K) 298. to 1200.1200. to 6000.
A 7.82368117.11230
B 15.252101.413011
C -9.192500-0.268365
D 2.3250600.017727
E -0.075905-2.345500
F -27.48891-34.50791
G 61.8184070.84610
H -24.30000-24.30000
ReferenceChase, 1998Chase, 1998
Comment Data last reviewed in December, 1970 Data last reviewed in December, 1970

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, Gas phase 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.

Chase, 1998
Chase, M.W., Jr., NIST-JANAF Themochemical Tables, Fourth Edition, J. Phys. Chem. Ref. Data, Monograph 9, 1998, 1-1951. [all data]

Okabe, 1970
Okabe, H., Photodissociation of HNCO in the vacuum ultraviolet; production of NCO A2Σ and NH (A3π, πC1), J. Chem. Phys., 1970, 53, 3507-3515. [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]

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]


Notes

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