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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

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
Deltar341.18 ± 0.61kcal/molD-EABradforth, Kim, et al., 1993gas phase; D-EA cycle requires a DH ca 4 kcal/mol weaker; B
Deltar344.7 ± 2.1kcal/molG+TSWight and Beauchamp, 1980gas phase; B
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; B
Deltar338.3 ± 2.0kcal/molIMREWight and Beauchamp, 1980gas phase; B

Vibrational and/or electronic energy levels

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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:
J - Marilyn E. Jacox
Shim - Takehiko Shimanouchi

State:   ?


 Energy 
 (cm-1
 Med.   Transition   «lambda»min 
 (nm) 
 «lambda»max 
 (nm) 
 References

Td gas 120 133 Okabe, 1970, 2

State:   ?


 Energy 
 (cm-1
 Med.   Transition   «lambda»min 
 (nm) 
 «lambda»max 
 (nm) 
 References

72940 gas 134 137 Okabe, 1970, 2

State:   ?


 Energy 
 (cm-1
 Med.   Transition   «lambda»min 
 (nm) 
 «lambda»max 
 (nm) 
 References

Td gas 147 163 Okabe, 1970, 2

State:   ?


 Energy 
 (cm-1
 Med.   Transition   «lambda»min 
 (nm) 
 «lambda»max 
 (nm) 
 References

Td gas 163 185 Okabe, 1970, 2

State:   ?


 Energy 
 (cm-1
 Med.   Transition   «lambda»min 
 (nm) 
 «lambda»max 
 (nm) 
 References

Td = 41000 gas 200U 244 Dixon and Kirby, 1968

State:   A


 Energy 
 (cm-1
 Med.   Transition   «lambda»min 
 (nm) 
 «lambda»max 
 (nm) 
 References

To = 32449 ± 20 gas A-X 228 282 Dixon and Kirby, 1968
Berghout, Crim, et al., 2000


Vib. 
sym. 
 No.   Approximate 
 type of mode 
 cm-1   Med.   Method   References

a' 3 HNC bend 1192 ± 10 gas PF Berghout, Crim, et al., 2000
4 NC stretch 1034 ± 20 gas PF Berghout, Crim, et al., 2000
5 NCO bend 599 ± 7 gas PF Berghout, Crim, et al., 2000

State:   X


Vib. 
sym. 
 No.   Approximate 
 type of mode 
 cm-1   Med.   Method   References

a' 1 NH stretch 3538.24 s gas IR Ra Herzberg and Reid, 1950
Reid, 1950
Teles, Maier, et al., 1989
Yamada, Winnewisser, et al., 1990
Brown, Berghout, et al., 1997
1 NH stretch 3516.8 w m Ar IR Teles, Maier, et al., 1989
1 NH stretch 3505.7 w m Ar IR Teles, Maier, et al., 1989
1 NH stretch 3514.7 Kr IR Pettersson, Khriachtchev, et al., 1999
1 NH stretch 3500.6 Kr IR Pettersson, Khriachtchev, et al., 1999
1 NH stretch 3485.2 Xe IR Pettersson, Khriachtchev, et al., 1999
1 NH stretch 3483.0 Xe IR Pettersson, Khriachtchev, et al., 1999
1 NH stretch 3479.9 Xe IR Pettersson, Khriachtchev, et al., 1999
2 NCO a-stretch 2268.89 vs gas IR Herzberg and Reid, 1950
Reid, 1950
Lemoine, Yamada, et al., 1982
Steiner, Polo, et al., 1983
Brown, Berghout, et al., 1997, 2
2 NCO a-stretch 2259.0 vs Ar IR Teles, Maier, et al., 1989
Crowley and Sodeau, 1989
2 NCO a-stretch 2261.6 Kr IR Pettersson, Khriachtchev, et al., 1999
2 NCO a-stretch 2254.4 Xe IR Pettersson, Khriachtchev, et al., 1999
3 NCO s-stretch 1327 w gas IR Herzberg and Reid, 1950
Reid, 1950
Brown, Berghout, et al., 1997, 2
4 HNC, NCO bend 776.62 w m gas IR Steiner, Wishah, et al., 1979
4 HNC, NCO bend 769.8 w m Ar IR Teles, Maier, et al., 1989
Crowley and Sodeau, 1989
4 HNC, NCO bend 763.6 Kr IR Pettersson, Khriachtchev, et al., 1999
4 HNC, NCO bend 765.1 Xe IR Pettersson, Khriachtchev, et al., 1999
4 HNC, NCO bend 760.3 Xe IR Pettersson, Khriachtchev, et al., 1999
5 HNC, NCO bend 577.35 w gas IR Herzberg and Reid, 1950
Reid, 1950
Steiner, Wishah, et al., 1979
5 HNC, NCO bend 573.7 w m Ar IR Teles, Maier, et al., 1989
Crowley and Sodeau, 1989
5 HNC, NCO bend 572.9 Kr IR Pettersson, Khriachtchev, et al., 1999
5 HNC, NCO bend 571.3 Kr IR Pettersson, Khriachtchev, et al., 1999
5 HNC, NCO bend 574.2 Xe IR Pettersson, Khriachtchev, et al., 1999
5 HNC, NCO bend 570.3 Xe IR Pettersson, Khriachtchev, et al., 1999
a 6 Torsion 656.29 gas IR Steiner, Wishah, et al., 1979
Fusina, Carlotti, et al., 1984
6 Torsion (1-0) 695.6 Kr IR Pettersson, Khriachtchev, et al., 1999
6 Torsion (1-0) 694.7 Xe IR Pettersson, Khriachtchev, et al., 1999

Additional references: Jacox, 1994, page 163; Jacox, 1998, page 236; Jacox, 2003, page 190; Ashby and Werner, 1966; Yamada, 1980; Steiner, Polo, et al., 1981

Notes

wWeak
mMedium
sStrong
vsVery strong
oEnergy separation between the v = 0 levels of the excited and electronic ground states.
dPhotodissociation threshold

References

Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, Gas phase ion energetics data, Vibrational and/or electronic energy levels, NIST Free Links, 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 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]

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]

Okabe, 1970, 2
Okabe, H., J. Chem. Phys., 1970, 53, 3507. [all data]

Dixon and Kirby, 1968
Dixon, R.N.; Kirby, G.H., Ultra-violet absorption spectrum of isocyanic acid, Trans. Faraday Soc., 1968, 64, 2002, https://doi.org/10.1039/tf9686402002 . [all data]

Berghout, Crim, et al., 2000
Berghout, H.L.; Crim, F.F.; Zyrianov, M.; Reisler, H., The electronic origin and vibrational levels of the first excited singlet state of isocyanic acid (HNCO), J. Chem. Phys., 2000, 112, 15, 6678, https://doi.org/10.1063/1.481242 . [all data]

Herzberg and Reid, 1950
Herzberg, G.; Reid, C., Infra-red spectrum and structure of the HNCO molecule, Discuss. Faraday Soc., 1950, 9, 92, https://doi.org/10.1039/df9500900092 . [all data]

Reid, 1950
Reid, C., Rotation-Vibration Spectra of Diatomic and Simple Polyatomic Molecules with Long Absorbing Paths V. The Spectrum of Isocyanic Acid, J. Chem. Phys., 1950, 18, 12, 1544, https://doi.org/10.1063/1.1747538 . [all data]

Teles, Maier, et al., 1989
Teles, J.H.; Maier, G.; Hess, B.A., Jr.; Schaad, L.J.; Winnewisser, M.; Winnewisser, B.P., The CHNO Isomers, Chem. Ber., 1989, 122, 4, 753, https://doi.org/10.1002/cber.19891220425 . [all data]

Yamada, Winnewisser, et al., 1990
Yamada, K.M.T.; Winnewisser, M.; Johns, J.W.C., High-resolution spectrum of the «nu»1 fundamental band of isocyanic acid, HNCO, J. Mol. Spectrosc., 1990, 140, 2, 353, https://doi.org/10.1016/0022-2852(90)90147-I . [all data]

Brown, Berghout, et al., 1997
Brown, S.S.; Berghout, H.L.; Crim, F.F., Raman spectroscopy of the «nu»1 N--H stretch fundamental in isocyanic acid (HNCO): State mixing probed by photoacoustic spectroscopy and by photodissociation of vibrationally excited states, J. Chem. Phys., 1997, 106, 14, 5805, https://doi.org/10.1063/1.473246 . [all data]

Pettersson, Khriachtchev, et al., 1999
Pettersson, M.; Khriachtchev, L.; Jolkkonen, S.; Rasanen, M., Photochemistry of HNCO in Solid Xe: Channels of UV Photolysis and Creation of H, J. Phys. Chem. A, 1999, 103, 45, 9154, https://doi.org/10.1021/jp992224d . [all data]

Lemoine, Yamada, et al., 1982
Lemoine, B.; Yamada, K.; Winnewisser, G., Diode Laser Spectrum of the Fundamental v2 Band of HNCO, Ber. Bunsenges. Phys. Chem., 1982, 86, 9, 795, https://doi.org/10.1002/bbpc.19820860906 . [all data]

Steiner, Polo, et al., 1983
Steiner, D.A.; Polo, S.R.; McCubbin, T.K.; Wishah, K.A., Infrared spectrum of the fundamental «nu»2 of isocyanic acid, J. Mol. Spectrosc., 1983, 98, 2, 453, https://doi.org/10.1016/0022-2852(83)90254-0 . [all data]

Brown, Berghout, et al., 1997, 2
Brown, S.S.; Berghout, H.L.; Crim, F.F., Raman spectroscopy of the N--C--O symmetric («nu»[sub 3]) and antisymmetric («nu»[sub 2]) stretch fundamentals in HNCO, J. Chem. Phys., 1997, 107, 23, 9764, https://doi.org/10.1063/1.475274 . [all data]

Crowley and Sodeau, 1989
Crowley, J.N.; Sodeau, J.R., Reaction between hydrocyanic acid and O(1D2) or O(3P) oxygen atoms in low-temperature matrixes, J. Phys. Chem., 1989, 93, 8, 3100, https://doi.org/10.1021/j100345a044 . [all data]

Steiner, Wishah, et al., 1979
Steiner, D.A.; Wishah, K.A.; Polo, S.R.; McCubbin, T.K., Infrared spectrum of isocyanic acid between 465 and 1100 cm-1, J. Mol. Spectrosc., 1979, 76, 1-3, 341, https://doi.org/10.1016/0022-2852(79)90233-9 . [all data]

Fusina, Carlotti, et al., 1984
Fusina, L.; Carlotti, M.; Carli, B., Infrared spectrum of HNCO between 8 and 80 cm, Can. J. Phys., 1984, 62, 12, 1452, https://doi.org/10.1139/p84-192 . [all data]

Jacox, 1994
Jacox, M.E., Vibrational and electronic energy levels of polyatomic transient molecules, American Chemical Society, Washington, DC, 1994, 464. [all data]

Jacox, 1998
Jacox, M.E., Vibrational and electronic energy levels of polyatomic transient molecules: supplement A, J. Phys. Chem. Ref. Data, 1998, 27, 2, 115-393, https://doi.org/10.1063/1.556017 . [all data]

Jacox, 2003
Jacox, M.E., Vibrational and electronic energy levels of polyatomic transient molecules: supplement B, J. Phys. Chem. Ref. Data, 2003, 32, 1, 1-441, https://doi.org/10.1063/1.1497629 . [all data]

Ashby and Werner, 1966
Ashby, R.A.; Werner, R.L., The infra-red absorption spectrum of DNCO, Spectrochim. Acta, 1966, 22, 7, 1345, https://doi.org/10.1016/0371-1951(66)80038-3 . [all data]

Yamada, 1980
Yamada, K., Molecular structure and centrifugal distortion constants of isocyanic acid from the microwave, millimeter wave, and far-infrared spectra, J. Mol. Spectrosc., 1980, 79, 2, 323, https://doi.org/10.1016/0022-2852(80)90217-9 . [all data]

Steiner, Polo, et al., 1981
Steiner, D.A.; Polo, S.R.; McCubbin, T.K.; Wishah, K.A., Infrared spectrum of the fundamental «nu», Can. J. Phys., 1981, 59, 10, 1313, https://doi.org/10.1139/p81-172 . [all data]


Notes

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