Home Symbol which looks like a small house Up Solid circle with an upward pointer in it

Isocyanic acid


Gas phase thermochemistry data

Go To: Top, Reaction thermochemistry data, Vibrational and/or electronic energy levels, 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
Deltafgas-101.67kJ/molReviewChase, 1998Data last reviewed in December, 1970
Deltafgas-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. - 1200.1200. - 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, Vibrational and/or electronic energy levels, 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
Deltar1427.5 ± 2.6kJ/molD-EABradforth, Kim, et al., 1993gas phase; D-EA cycle requires a DH ca 4 kcal/mol weaker
Deltar1442. ± 8.8kJ/molG+TSWight and Beauchamp, 1980gas phase
Quantity Value Units Method Reference Comment
Deltar1400.6 ± 3.0kJ/molH-TSBradforth, Kim, et al., 1993gas phase; D-EA cycle requires a DH ca 4 kcal/mol weaker
Deltar1415. ± 8.4kJ/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
Deltar180. ± 13.kJ/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
Deltar243. ± 9.2kJ/molN/ATaft, 1987gas phase; value altered from reference due to change in acidity scale

Vibrational and/or electronic energy levels

Go To: Top, Gas phase thermochemistry data, 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:
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, Vibrational and/or electronic energy levels, 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]

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

Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, Vibrational and/or electronic energy levels, References