Isocyanic acid
- Formula: CHNO
- Molecular weight: 43.0247
- IUPAC Standard InChI: InChI=1S/CHNO/c2-1-3/h2H
- IUPAC Standard InChIKey: OWIKHYCFFJSOEH-UHFFFAOYSA-N
- CAS Registry Number: 75-13-8
- Chemical structure:
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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 |
|---|---|---|---|---|---|
| ΔfH°gas | -101.67 | kJ/mol | Review | Chase, 1998 | Data last reviewed in December, 1970 |
| ΔfH°gas | -97. ± 13. | kJ/mol | Ion | Okabe, 1970 | ALS |
| Quantity | Value | Units | Method | Reference | Comment |
| S°gas,1 bar | 238.22 | J/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 (J/mol*K)
H° = standard enthalpy (kJ/mol)
S° = standard entropy (J/mol*K)
t = temperature (K) / 1000.
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| Temperature (K) | 298. to 1200. | 1200. to 6000. |
|---|---|---|
| A | 32.73428 | 71.59786 |
| B | 63.81479 | 5.912034 |
| C | -38.46142 | -1.122839 |
| D | 9.728052 | 0.074171 |
| E | -0.317587 | -9.813573 |
| F | -115.0136 | -144.3811 |
| G | 258.6482 | 296.4201 |
| H | -101.6712 | -101.6712 |
| 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, 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° | 1427.5 ± 2.6 | kJ/mol | D-EA | Bradforth, Kim, et al., 1993 | gas phase; D-EA cycle requires a DH ca 4 kcal/mol weaker |
| ΔrH° | 1442. ± 8.8 | kJ/mol | G+TS | Wight and Beauchamp, 1980 | gas phase |
| Quantity | Value | Units | Method | Reference | Comment |
| ΔrG° | 1400.6 ± 3.0 | kJ/mol | H-TS | Bradforth, Kim, et al., 1993 | gas phase; D-EA cycle requires a DH ca 4 kcal/mol weaker |
| ΔrG° | 1415. ± 8.4 | kJ/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° | 180. ± 13. | kJ/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° | 243. ± 9.2 | kJ/mol | N/A | Taft, 1987 | gas 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
- Symbols used in this document:
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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