The Formation of Cyanoketene (NCCHCO) and the Isomer NCCCHO from Anionic Precursors in the Gas Phase. The Rearrangement of NCCCHO to NCCHCO

Abstract

It has been reported that irradiation of cyanoacetylene and ozone on a water ice surface at 255 nm yields both hydrogen peroxide and cyanoacetylene (NCCHCO), and it has been proposed that this overall process may involve a crucial step where NCCCHO rearranges to NCCHCO.The isomers NCCHCO and NCCCHO have been prepared in this study by one-electron vertical oxidation of [NCCHCO]-• and [NCCCHO]-• in collision cells of a VG ZAB 2HF mass spectrometer. -NR+ experiments indicate that singlet NCCHCO is stable for the microsecond duration of the experiment. In contrast, calculations at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31G(d) level of theory indicate that singlet NCCCHO does not occupy a minimum on the singlet neutral potential surface, but rearranges to singlet NCCHCO. Some of the singlet NCCHCO neutrals formed in this way are stable, whereas others have sufficient excess energy to effect decomposition to give NCCH and CO. Triplet NCCCHO is stable but, when energized, may (i) rearrange over a barrier of 49.0 kcal mol-1 to give triplet NCCHCO, which is energized and decomposes to NCCH and CO, and/or (ii) undergo intersystem crossing to yield singlet NCCHCO. It is concluded that, in principle, the rearrangement NCCCHO to NCCHCO could occur in regions of interstellar ice.

Anions [N(CH2)3]− and [ON(CH2)2]− are Stable in the Gas Phase, but Can They Be Charge Stripped to Form the Radicals N(CH2)3 and ON(CH2)2? A Joint Experimental and Theoretical Study

“…Any differences between the two spectra indicate a rearrangement and/or decomposition of the neutrals produced by the -Nr + process, which provides information concerning the structure of the neutrals formed by the charge-stripping process. 13 As described above, the differences between the -Nr + and cr + spectra are due to reactions of the neutral during the microsecond period before it is ionised. Although the c 3 H 6 N + potential surface has been mapped by others, 6,7 we have carried out calculations on those positive ion isomers which might, in principle, be formed from energised N(cH 2 ) 3 and have done the same thing for the oN(cH 2 ) 2 system.…”

“…charge reversal (cr + ) spectra 11,12 were recorded using single-collision conditions in collision cell 1 (o 2 , 80% transmission of main beam). comparison ofcr + and -Nr + data for a given parent anion provides information concerning the neutral formed from the parent anion: see reference 13 for a full description of this procedure.…”

Theoretical study of OCCHCN as a potential alternative insulation gas for SF6

“…The neutral and ion states of the studied molecules were confirmed by normal-mode analysis with real frequency corresponding to all of the vibrating modes. The geometric parameters of R, IM3, IM4, TS4 and TS5 are compared with the corresponding values calculated by McAnoy and co-workers 19 are gathered in Table II. It can be seen that our obtained geometric parameters are very close to those reported by McAnoy.…”

“…It can be seen that our obtained geometric parameters are very close to those reported by McAnoy. 19 Table III lists the harmonic vibrational frequencies of the reactant, intermediates, products, and transition states calculated at the same level as well as the available experimental values. 28,29 For the species OCCHCN, CO, HCNC, and HCCN, the calculated frequencies are in good agreement with the experimental values.…”

“…17 Thus, that the compound OCCHCN with double bond (C= =C and C= =O) and triple bond (C≡ ≡N) could have high electron affinity, and Luly and Richar 18 have suggested that it could be used as SF 6 alternative gas. McAnoy and the co-workers 19 have showed that the rearrangement of NCCCHO to NCCHCO can occur and the singlet OCCHCN can decompose to HCCN and CO through mass spectrometric method and quantum chemical calculations. However, other channels of the possible cleavage reactions of OCCHCN have not been reported so far.…”