Determination of the heats of formation of CCCN and HCCCN

Abstract

The electronic structure, vibrational spectra, and thermodynamic stability of CCCN and HCCCN have been determined using ab initio molecular orbital theory. The heat of formation for HCCCN was determined using Gaussian-2 theory (G2) and was found to be 91.5±2 kcal mol−1. There is good agreement between the G2 value and that determined using an isodesmic reaction (i.e., one in which both the number and types of bonds are conserved), which yields 90.7±2 kcal mol−1. The heat of formation for the CCCN radical is 178.2±2 kcal mol−1. These data are used to compute the bond dissociation energies in HCCCN, D0(C–C) and D0(C–H), which are important in assessing the chemistry in Titan’s atmosphere, as well as in other interstellar media.

Ionization photophysics and spectroscopy of cyanoacetylene

“…84 We note also the ab initio calculations of Francisco and Richardson at the Gaussian-2 theory level which give 382 ± 8 kJ/mol, while an isodesmic reaction evaluation gives 379 ± 8 kJ/mol. 80 Using an enthalpic shift procedure Golovin and Takhistov 85 89 The reported experimental and calculated values of IE(CN) just mentioned thus cover the wide range 13.598-14.5 eV. We note also that a quite thorough report dating from 1965 elaborates the determination of eight different values of IE(CN) and recommends the lowest value, IE(CN) = 13.4 eV.…”

Structure, Spectroscopic Properties and Reactions of Interstellar Molecule HC2N and Isomers :Ab initio Study

“…Typical example is cyanopolyacetylenes HC 2n+1 N. HC 11 N 8 is one of the largest molecules observed in interstellar medium. The structures and infrared frequencies of these molecules were measured, and numerous ab initio computations [9][10][11][12] were also carried out.…”

A theoretical study on the mechanism of the reaction between azacyclopropenylidene and oxirane

“…Compared with the isolated azacyclopropenylidene, the bond length of C 2 -N in the IM is shortened by 0.0018 nm. Therefore, the IM is the common intermediate for pathway (1) and pathway (2). Therefore, the ring-tension of the R1 fragment in the IM is larger than that of the iso-lated R1.…”

“…1, C 2 and N adopt sp 2 hybridization in the IM. On the other hand, through H-transfer step and subsequent ring-opening step at the C-N bond, the IM can turn into product P2, which is designated pathway (2). The angle of C 1 NC 2 in the IM is 60.9°, which is decreased slightly by 1.0° relative to that in isolated azacyclopropenylidene.…”