Infrared absorption of 3-propenonyl (⋅CH2CHCO) radical generated upon photolysis of acryloyl chloride [CH2CHC(O)Cl] in solid para-H2

Abstract

Irradiation at 193 nm of a p-H2 matrix containing acryloyl chloride CH2CHC(O)Cl at 3.2 K yielded infrared absorption lines at 3143.6 (ν1), 3057.0 (ν2), 3048.0 (ν3), 2103.1 (ν4), 1461.0 (ν5), 1349.8 (ν6), 1223.7 (ν11+ν12 or 2ν12), 1092.8 (ν8), 918.1 (ν9), 691.0 (ν10), 624.3 (ν11), and 597.1 (ν12) cm(-1) that are assigned to the 3-propenonyl (·CH2CHCO) radical. The assignments are based on the photolytic behavior and a comparison of observed vibrational wavenumbers and infrared intensities with those predicted with the B3PW91/aug-cc-pVDZ method. The observation is consistent with a major radical formation channel CH2CHCO + Cl followed by escape of the Cl atom from the original p-H2 cage. The observation of 3-propenonyl (·CH2CHCO) radical but not 3-propenalyl (s-cis- or s-trans-CH2CHĊO) radical indicates that the former is the most stable isomer and that the barrier heights for conversion from s-cis- or s-trans-CH2CHĊO to ·CH2CHCO are small.

Two HCl-Elimination Channels and Two CO-Formation Channels Detected with Time-Resolved Infrared Emission upon Photolysis of Acryloyl Chloride [CH2CHC(O)Cl] at 193 nm

“…13 These results are consistent with a major radical formation channel CH 2 CHCO + Cl followed by escape of the Cl atom from the original site in p-H 2 , which has a diminished cage effect. The observation of 3-propenonyl (•CH 2 CHCO) radical but not 3-propenalyl (s-cis-or s-trans-CH 2 CHĊO) radical indicates that the former is the most stable isomer and that the barrier heights for conversion from s-cis-or s-trans-CH 2 CHĊO to •CH 2 CHCO are small.…”

“…Prasanta and Lee irradiated a p -H 2 matrix containing CH 2 CHC­(O)Cl at 3.2 K with light at 193 nm and observed infrared (IR) absorption lines that were assigned to the 3-propenonyl (·CH 2 CHCO) radical; no line of CH 2 ClCHCO was observed . These results are consistent with a major radical formation channel CH 2 CHCO + Cl followed by escape of the Cl atom from the original site in p -H 2 , which has a diminished cage effect.…”

“…The calculated absorption cross section of CH 2 CHC(O)Cl at 193 nm is 4×10 −17 cm 2 molecule −1 . 13 The power dependence of the emission signals was tested; the order of power dependence 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 8 was determined to be 0.95 ± 0.05 for light at 193 nm with fluence < 15 mJ cm −2 .…”

“…We chose for our Franck-Condon approximation the distance of closest approach in Figure 11, thus assuming that the H-Cl bond is formed there, 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 observed, corresponding to energy difference of 1.6 ± 0.7 kJ mol −1 if a Boltzmann distribution at 298 K be assumed; 13 for v = 0) shown in Table S1 of Supplementary Information, we observed <7 % increase in population for t > 1 µs; this increase in population is presumed to be due to formation of HCl due to a secondary reaction. The secondary reaction of Cl to produce HCl is hence negligible under our experimental conditions.…”

Excited-State Ring-Opening Mechanism of Cyclic Ketones: A MS-CASPT2//CASSCF Study

“…Experimentally, many groups have explored photodissociation dynamics of aliphatic ketones. For example, the Butler group − has studied a series of carbonyl halides, for example, acetyl chloride and chloroacetone; Zewail et al − employed femtosecond-resolved spectra to study ultrafast bond-making and -breaking processes related to Norrish type I and II reactions; Lee and his co-workers − used crossed molecular beam, multimass ion imaging, and infrared spectroscopy techniques to explore photodissociation dynamics of various carbonyl compounds in vacuo and in para hydrogen matrices. Furthermore, other groups have performed many excellent experimental studies in vacuo and in condensed phases. − These numerous experiments also attracted much attention of theoretical chemists.…”