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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
Deltafgas-24.300kcal/molReviewChase, 1998Data last reviewed in December, 1970
Deltafgas-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. - 1200.1200. - 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

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

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
Deltar341.18 ± 0.61kcal/molD-EABradforth, Kim, et al., 1993gas phase; D-EA cycle requires a DH ca 4 kcal/mol weaker
Deltar344.7 ± 2.1kcal/molG+TSWight and Beauchamp, 1980gas phase
Quantity Value Units Method Reference Comment
Deltar334.74 ± 0.71kcal/molH-TSBradforth, Kim, et al., 1993gas phase; D-EA cycle requires a DH ca 4 kcal/mol weaker
Deltar338.3 ± 2.0kcal/molIMREWight and Beauchamp, 1980gas phase

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

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

Quantity Value Units Method Reference Comment
Deltar43.1 ± 3.0kcal/molN/ATaft, 1987gas phase; value altered from reference due to change in acidity scale

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

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

Quantity Value Units Method Reference Comment
Deltar58.1 ± 2.2kcal/molN/ATaft, 1987gas phase; value altered from reference due to change in acidity scale

References

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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 A2«SIGMA» and NH (A3«pi», «pi»C1), 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

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