Synthesis of interstellar 1,3,5-heptatriynylidyne, C7H(X Π2), via the neutral-neutral reaction of ground state carbon atom, C(P3), with triacetylene, HC6H (X Σ1g+)

Abstract

The reaction of ground-state carbon atom with a polyyne, triacetylene (HC6H) is investigated theoretically by combining ab initio calculations for predicting reaction paths, RRKM theory to yield rate constant for each path, and a modified Langevin model for estimating capturing cross sections. The isomerization and dissociation channels for each of the five collision complexes are characterized by utilizing the unrestricted B3LYP/6-311G(d,p) level of theory and the CCSD(T)/cc-pVTZ calculations. Navigating with the aid of RRKM rate constants through web of ab initio paths composed of 5 collision complexes, 108 intermediates, and 20 H-dissociated products, the most probable paths, reduced to around ten species at collision energies of 0 and 10 kcal/mol, respectively, are identified and adopted as the reaction mechanisms. The rate equations for the reaction mechanisms are solved numerically such that the evolutions of concentrations with time for all species involved are obtained and their lifetimes deduced. This study predicts that the five collision complexes, c1–c5, would produce a single final product, C7H (p1)+H, via the most stable intermediate, carbon chain HC7H (i1); namely, C+HC6H→HC7H→C7H+H. Our investigation indicates that the title reaction is efficient to form astronomically observed C7H in cold molecular clouds, where a typical translational temperature is 10 K.

N-(4-Chlorobutanoyl)-N′-phenylthiourea

“…For the biological properties of thiourea derivatives, see; Sun et al (2006); Figueiredo et al (2006). For a related structure, see: Othman et al (2010); For standard bond lengths, see: Allen et al (1987).…”

“…The continuing work on the synthesis of thiourea derivatives is driven by their chemical and biological properties (Sun et al ,2006). Some thiourea derivatives such as N- [1-(4R)…”

Theoretical Studies of Two Key Low-Lying Carbenes of C5H2Missing in the Laboratory

“…However, one of the isomers of SiC 3 , which contains a transannular C–C bond (rhomboidal geometry) has been confirmed in the evolved carbon star, IRC + 10216 based on laboratory rest frequencies . Within C 5 H 2 elemental composition, the elusive aromatic carbene, 2-methylenebicyclo[1.1.0]­but-1(3)-en-4-ylidene ( 9 ; see Figure ), also contains a transannular C–C bond but less attention has been paid to this molecule. − Of note, for the confirmation of four C n H 2 carbenes in nonterrestrial environments, − identification of the same in laboratories (terrestrial environments) is a crucial factor. ,,− Therefore, considering the astrochemical relevance, available laboratory astrophysics data, and enhancing our understanding of structure and bonding of various C n H 2 isomers, where, n = 2, 3, ,,,,− 4, ,,− 5, − 6, ,,− 7, ,,− 8, ,,, 9, ,,,,…”

The quest for the carbene bent-pentadiynylidene isomer of C5H2

“…However, we affirm that at the CCSDT(Q)/CBS level of theory including zero-point vibrational energy (ZPVE) corrections at the fc-CCSD(T)/cc-pVTZ level of theory, the linear isomer (1) is the most stable structure (Table 1) on the C 5 H 2 PES. The poor performance of density functional theory (DFT) for similar relative energies has been previously noted in the case of C 7 H 2 isomers, in particular for the low-lying non-linear isomers [59,60,61,62] (see also ref. [63] for a comprehensive survey of the performance of a wide range of DFT methods for challenging structural relative energies).…”