Isocyanic acid


Gas phase thermochemistry data

Go To: Top, Reaction thermochemistry data, References, Notes

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-101.67kJ/molReviewChase, 1998Data last reviewed in December, 1970
Δfgas-97. ± 13.kJ/molIonOkabe, 1970ALS
Quantity Value Units Method Reference Comment
gas,1 bar238.22J/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 (J/mol*K)
    H° = standard enthalpy (kJ/mol)
    S° = standard entropy (J/mol*K)
    t = temperature (K) / 1000.

View plot Requires a JavaScript / HTML 5 canvas capable browser.

View table.

Temperature (K) 298. to 1200.1200. to 6000.
A 32.7342871.59786
B 63.814795.912034
C -38.46142-1.122839
D 9.7280520.074171
E -0.317587-9.813573
F -115.0136-144.3811
G 258.6482296.4201
H -101.6712-101.6712
ReferenceChase, 1998Chase, 1998
Comment Data last reviewed in December, 1970 Data last reviewed in December, 1970

Reaction thermochemistry data

Go To: Top, Gas phase thermochemistry data, References, Notes

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

Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. A general reaction search form is also available. Future versions of this site may rely on reaction search pages in place of the enumerated reaction displays seen below.

Individual Reactions

CNO- + Hydrogen cation = Isocyanic acid

By formula: CNO- + H+ = CHNO

Quantity Value Units Method Reference Comment
Δr1427.5 ± 2.6kJ/molD-EABradforth, Kim, et al., 1993gas phase; D-EA cycle requires a DH ca 4 kcal/mol weaker
Δr1442. ± 8.8kJ/molG+TSWight and Beauchamp, 1980gas phase
Quantity Value Units Method Reference Comment
Δr1400.6 ± 3.0kJ/molH-TSBradforth, Kim, et al., 1993gas phase; D-EA cycle requires a DH ca 4 kcal/mol weaker
Δr1415. ± 8.4kJ/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
Δr180. ± 13.kJ/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
Δr243. ± 9.2kJ/molN/ATaft, 1987gas phase; value altered from reference due to change in acidity scale

References

Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry 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]

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]


Notes

Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, References