Isocyanic acid
- Formula: CHNO
- Molecular weight: 43.0247
- IUPAC Standard InChIKey: OWIKHYCFFJSOEH-UHFFFAOYSA-N
- CAS Registry Number: 75-13-8
- Chemical structure:
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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 |
---|---|---|---|---|---|
ΔfH°gas | -24.300 | kcal/mol | Review | Chase, 1998 | Data last reviewed in December, 1970 |
ΔfH°gas | -23.1 ± 3.2 | kcal/mol | Ion | Okabe, 1970 | ALS |
Quantity | Value | Units | Method | Reference | Comment |
S°gas,1 bar | 56.936 | cal/mol*K | Review | Chase, 1998 | Data 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 | 7.823681 | 17.11230 |
B | 15.25210 | 1.413011 |
C | -9.192500 | -0.268365 |
D | 2.325060 | 0.017727 |
E | -0.075905 | -2.345500 |
F | -27.48891 | -34.50791 |
G | 61.81840 | 70.84610 |
H | -24.30000 | -24.30000 |
Reference | Chase, 1998 | Chase, 1998 |
Comment | Data last reviewed in December, 1970 | Data last reviewed in December, 1970 |
Reaction thermochemistry data
Go To: Top, Gas phase thermochemistry data, Gas phase ion energetics 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- + =
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
ΔrH° | 341.18 ± 0.61 | kcal/mol | D-EA | Bradforth, Kim, et al., 1993 | gas phase; D-EA cycle requires a DH ca 4 kcal/mol weaker |
ΔrH° | 344.7 ± 2.1 | kcal/mol | G+TS | Wight and Beauchamp, 1980 | gas phase |
Quantity | Value | Units | Method | Reference | Comment |
ΔrG° | 334.74 ± 0.71 | kcal/mol | H-TS | Bradforth, Kim, et al., 1993 | gas phase; D-EA cycle requires a DH ca 4 kcal/mol weaker |
ΔrG° | 338.3 ± 2.0 | kcal/mol | IMRE | Wight and Beauchamp, 1980 | gas phase |
(CAS Reg. No. 1140500-24-8 • 4294967295) + = 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 |
---|---|---|---|---|---|
ΔrH° | 43.1 ± 3.0 | kcal/mol | N/A | Taft, 1987 | gas phase; value altered from reference due to change in acidity scale |
(CAS Reg. No. 67131-48-0 • 4294967295) + = 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 |
---|---|---|---|---|---|
ΔrH° | 58.1 ± 2.2 | kcal/mol | N/A | Taft, 1987 | gas phase; value altered from reference due to change in acidity scale |
Gas phase ion energetics data
Go To: Top, Gas phase thermochemistry data, 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 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 ± 0.005 | eV | N/A | N/A | L |
Quantity | Value | Units | Method | Reference | Comment |
Proton affinity (review) | 180. | kcal/mol | N/A | Hunter and Lias, 1998 | HL |
Quantity | Value | Units | Method | Reference | Comment |
Gas basicity | 171.8 | kcal/mol | N/A | Hunter and Lias, 1998 | HL |
Ionization energy determinations
IE (eV) | Method | Reference | Comment |
---|---|---|---|
11.595 ± 0.005 | PI | Ruscic and Berkowitz, 1994 | LL |
11.62 ± 0.02 | PE | Cradock, Ebsworth, et al., 1972 | LLK |
11.60 ± 0.01 | PE | Rowland, Eland, et al., 1968 | RDSH |
Appearance energy determinations
Ion | AE (eV) | Other Products | Method | Reference | Comment |
---|---|---|---|---|---|
CHO+ | 15.52 | N | EI | Compernolle, 1975 | LLK |
CHO+ | 15.76 ± 0.15 | N | EI | Bogan and Hand, 1971 | LLK |
CNO+ | ≤16.532 | H | PI | Ruscic and Berkowitz, 1994 | LL |
CNO+ | 16.66 ± 0.15 | H | EI | Bogan and Hand, 1971 | LLK |
CNO+ | ≤16.1 | H | EI | Rowland, Eland, et al., 1968 | RDSH |
NH+ | 17.26 ± 0.15 | CO | EI | Bogan and Hand, 1971 | LLK |
NH+ | ≤17.7 | CO | EI | Rowland, Eland, et al., 1968 | RDSH |
NO+ | 15.76 ± 0.15 | ? | EI | Bogan and Hand, 1971 | LLK |
De-protonation reactions
CNO- + =
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
ΔrH° | 341.18 ± 0.61 | kcal/mol | D-EA | Bradforth, Kim, et al., 1993 | gas phase; D-EA cycle requires a DH ca 4 kcal/mol weaker; B |
ΔrH° | 344.7 ± 2.1 | kcal/mol | G+TS | Wight and Beauchamp, 1980 | gas phase; B |
Quantity | Value | Units | Method | Reference | Comment |
ΔrG° | 334.74 ± 0.71 | kcal/mol | H-TS | Bradforth, Kim, et al., 1993 | gas phase; D-EA cycle requires a DH ca 4 kcal/mol weaker; B |
ΔrG° | 338.3 ± 2.0 | kcal/mol | IMRE | Wight and Beauchamp, 1980 | gas phase; B |
Vibrational and/or electronic energy levels
Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, Gas phase ion energetics 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 | λmin (nm) |
λmax (nm) |
References | ||
---|---|---|---|---|---|---|---|
Td | gas | 120 | 133 | Okabe, 1970, 2 | |||
State: ?
Energy (cm-1) |
Med. | Transition | λmin (nm) |
λmax (nm) |
References | ||
---|---|---|---|---|---|---|---|
72940 | gas | 134 | 137 | Okabe, 1970, 2 | |||
State: ?
Energy (cm-1) |
Med. | Transition | λmin (nm) |
λmax (nm) |
References | ||
---|---|---|---|---|---|---|---|
Td | gas | 147 | 163 | Okabe, 1970, 2 | |||
State: ?
Energy (cm-1) |
Med. | Transition | λmin (nm) |
λmax (nm) |
References | ||
---|---|---|---|---|---|---|---|
Td | gas | 163 | 185 | Okabe, 1970, 2 | |||
State: ?
Energy (cm-1) |
Med. | Transition | λmin (nm) |
λmax (nm) |
References | ||
---|---|---|---|---|---|---|---|
Td = 41000 | gas | 200U | 244 | Dixon and Kirby, 1968 | |||
State: A
Energy (cm-1) |
Med. | Transition | λmin (nm) |
λmax (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
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
w | Weak |
m | Medium |
s | Strong |
vs | Very strong |
o | Energy separation between the v = 0 levels of the excited and electronic ground states. |
d | Photodissociation threshold |
References
Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, Gas phase ion energetics 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 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]
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 ν1 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 ν1 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 ν2 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 (ν[sub 3]) and antisymmetric (ν[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 ν,
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, Gas phase ion energetics data, Vibrational and/or electronic energy levels, References
- Symbols used in this document:
AE Appearance energy IE (evaluated) Recommended ionization energy S°gas,1 bar Entropy of gas at standard conditions (1 bar) ΔfH°gas Enthalpy of formation of gas at standard conditions ΔrG° Free energy of reaction at standard conditions ΔrH° Enthalpy of reaction at standard conditions - Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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