The heat of formation of NCO has been determined rigorously by state‐of‐the‐art ab initio electronic structure methods, including Mo/ller–Plesset perturbation theory from second through fifth order (MP2–MP5) and coupled‐cluster and Brueckner methods incorporating various degrees of excitation [CCSD, CCSD(T), BD, BD(T), and BD(TQ)]. Five independent reactions were investigated to establish a consistent value for ΔHf,0○(NCO): (a) HNCO(X̃ 1A′)→H(2S)+NCO(2Π), (b) HNCO(X̃ 1A′)→H++NCO−, (c) N(4S)+CO→NCO(2Π), (d) HCN+O(3P)→H(2S)+NCO(2Π), and (e) NH(3Σ−)+CO→H(2S)+NCO(2Π). The one‐particle basis sets employed in the study were comprised of as many as 377 contracted Gaussian functions and ranged in quality from [4s2p1d] to [14s9p6d4f] on the (C,N,O) atoms and from [2s1p] to [8s6p4d] on hydrogen. After the addition of bond additivity corrections evaluated from related reactions of precisely known thermochemistry, all five approaches were found to converge on the value ΔHf,0○(NCO)=31.4(5) kcal mol−1. Appurtenant refinements were obtained for the heat of formation of isocyanic acid, ΔHf,0○(HNCO)=−27.5(5) kcal mol−1, and hydrogen cyanide, ΔHf,0○(HCN)=31.9(5) kcal mol−1. The final proposals for ΔHf,0○(NCO) and ΔHf,0○(HNCO) resolve outstanding discrepancies with experiment and provide updates for thermochemical cycles of relevance to combustion chemistry.
Skip Nav Destination
Article navigation
15 September 1993
Research Article|
September 15 1993
The heat of formation of NCO
Allan L. L. East;
Allan L. L. East
Department of Chemistry, Stanford University, Stanford, California 94305
Search for other works by this author on:
Wesley D. Allen
Wesley D. Allen
Department of Chemistry, Stanford University, Stanford, California 94305
Search for other works by this author on:
J. Chem. Phys. 99, 4638–4650 (1993)
Article history
Received:
April 29 1993
Accepted:
June 01 1993
Citation
Allan L. L. East, Wesley D. Allen; The heat of formation of NCO. J. Chem. Phys. 15 September 1993; 99 (6): 4638–4650. https://doi.org/10.1063/1.466062
Download citation file:
Pay-Per-View Access
$40.00
Sign In
You could not be signed in. Please check your credentials and make sure you have an active account and try again.
Citing articles via
DeePMD-kit v2: A software package for deep potential models
Jinzhe Zeng, Duo Zhang, et al.
A theory of pitch for the hydrodynamic properties of molecules, helices, and achiral swimmers at low Reynolds number
Anderson D. S. Duraes, J. Daniel Gezelter
CREST—A program for the exploration of low-energy molecular chemical space
Philipp Pracht, Stefan Grimme, et al.
Related Content
NBC Studio Design
J. Acoust. Soc. Am. (July 1936)
In-place analysis and load formulation of BAJT-H fixed offshore jacket platform
AIP Conf. Proc. (December 2023)
Recent enhancement of the RCC technology in dam engineering
AIP Conf. Proc. (February 2020)
Air handler sound power prediction method based on ARI Standard 260
J Acoust Soc Am (November 2000)
A Spectrophotometer for Measurement of Optical Filters
Rev. Sci. Instrum. (August 1941)