The Thermal Decomposition of Haloacetic Acids: a Laser Pyrolysis and Semiempirical Study.

Abstract

Infrared laser-powered homogeneous pyrolysis, coupled with Fourier-transform infrared measurement of product distributions, has demonstrated that four different unimolecular mechanisms are significant in the initiation of gas-phase thermal decomposition of CH3COOH (1), CF3COOH (2), CH2ClCOOH (3), CHCl2COOH (4), CCl3COOH (5), CH2BrCOOH (6), and CH2ICOOH (7): decarboxylation and dehydration for (1); H-X elimination for (2)-(6); and C-X bond homolysis for (6) and (7). These conclusions are supported by the semiempirical calculation of activation energies for the possible pathways.

Laser pyrolysis studies of the thermal decomposition of chlorinated organic compounds. Part 1—acyl chlorides

“…[8][9][10][11] This has been demonstrated in systems as varied as precursors to chemical vapour deposition, [12][13][14][15][16] various cyclic systems 17,18 and small organic molecules. 19 We have also shown that the pyrolysis of acyl chlorides is a good source of short-lived ketenes for spectroscopic study. [20][21][22] Here we report a systematic study of a range of acyl chlorides selected to emphasise a number of aspects of their decomposition chemistry.…”

The ν2+ν4 Band of Carbonyl Fluoride

“…Spectra assignable to COF 2 were observed in the pyrolysis of many C/O/F systems; for the measurements described here, strong clean spectra were generated by pyrolysis of trifluoroacetic acid. Under the conditions described above, COF 2 forms as a secondary product of decomposition; initial loss of HF results in formation of difluorooxiranone, which readily decarbonylates to yield COF 2 (19). It may also be formed by the subsequent reaction of CF 3 radicals with oxygen-containing compounds and loss of F atoms.…”

“…All other parameters were well determined, although those relating to asymmetry showed significant correlation, a consequence of the limited number of resolved K c -doublets observed. The rms deviation of the final fit was 0.0006 cm −1 , somewhat better than the estimated accuracy of the measurements, with no sign of residual systematic (6,5) 12 (7,6) 2187.7052 2187.7055 −0.0003 11 (6,6) 11 (7,5) 2192.8155 2192.8153 0.0002 11 (6,6) 12 (5, (12,13) 26 (13,14) 2178.7175 2178.7178 −0.0003 25 (12,14) 26 (11,15) 2179.1316 2179.1313 0.0002 25 (10,16) 26 (9,17) 2179.9644 2179.9632 0.0012 25 (8,17) 26 (9,18) 2180.3811 2180.3815 −0.0004 (12,16) 28 (11,17) 2178.1376 2178.1381 −0.0005 27 (10,17) 28 (11,18) 2178.5565 2178.5562 0.0004 27 (10,18) 28 (9,19) 2178.9767 2178.9759 0.0008 27 (8,19) 28 (9,20) 2179.3980 2179.3972 0.0008 27 (8,20) 28 …”

Laser pyrolysis studies of β-diketonate chemical vapour deposition precursors. Part 1: β-diketones

“…The value of this multilateral approach has been demonstrated in systems as varied as precursors to chemical vapour deposition, [7][8][9][10][11] various cyclic systems 12,13 and small organic molecules. 14 In the present work, we report IR LPHP studies of the three common diketones acacH, 1,1,1,5,5,5-hexafluoropentane-2,4dione (hexafluoroacetylacetone, hfacH, 2), and 2,2,6,6-tetramethylheptane-3,5-dione (thdH, 3). Not only are complexes derived from these used widely as deposition precursors, but the compounds themselves exhibit a range of thermal decomposition behaviour, resulting from subtle changes in the balance of keto-enol equilibria and bond strengths.…”