Chloroacetone, photolysis

Chloroacetone photolysis at A 3130 A has been studied by Strachan and Blacet . Large amounts of hydrogen chloride and acetone are produced at room temperature with only very small quantities of methyl chloride, methane and carbon monoxide. The nature of the products suggests that the primary process is predominantly of Type 3, viz. 

The photolysis of chloroacetone with light of wavelength 3130 A. has been studied in detail by Strachan and Blacet.44 At room temperature, the negligible amounts of carbon monoxide, methyl chloride, methane, and ethane formed and the preponderance of hydrogen chloride and acetone in the products of photolysis, suggested that the primary step was of type C. 

From Other Sulphur Heterocycles. The reaction of (46) with 2 eq. of bromine in CHjC gave (47), except for, (46d), which directly gave (48a). Further bromination of (47a) gave (48b). The formation of (47) from (46) has been assumed to proceed via (49) to (53).15 The reaction of (54) with chloroacetone under basic conditions unexpectedly yielded (55) in 44% yield.16 Photolysis of (56) gave tetraphenylthiophen, tetraphenyl-1,4-dithiine, diphenyl-acetylene and sulphur. The products are assumed to be formed via the dimer (57) and (58), which were isolable under appropriate conditions. Photolysis of (56) in the presence of dimethyl acetylenedicarboxylate gave a 17% yield of dimethyl 2,5-dif)henyl-thiophen-3,4-dicarboxylate.17 The reaction of (59) with diphenyl-acetylene at 300°C gave tetraphenylthiophen.1 ... 

UV-induced reactions of chloroacetone in a cryogenic Ar matrix were investigated by Tanaka, Urashima and Nishikiori/ Accompanying the photoinduced isomerizations of gawc/ze-chloroacetone to -chloro-acetone and hypochlorous acid 1-methylethenyl ester, the photolysis of the compound to yield CH2=C=0 and a cyclopropanone HCl complex was observed. The complex was also shown to further decompose into CH2=CH2, CO and HCl, while the hypochlorous acid 1-methylethenyl ester was further converted to 2-chloro-2-methyloxirane. 

Waschewsky et al. (1994) used crossed laser-molecular beam experiments to monitor the competition between photodissociation pathways in chloroacetone. Their studies proved that C—C bond fission, process (II), competes with C—Cl bond fission, process (1), in C1CH2C(0)CH3 photolysis at 308 nm, although the latter process is favored. Several kJ of translational energy were evident in the translation of the initial products of the two competing dissociation pathways. The authors point out that this may indicate that, for both channels, dissociation proceeds via a reaction coordinate that has a significant exit barrier (barrier to reverse reaction), so fragments exert a repulsive force on each other as they separate. The pathway to dissociation probably does not involve... 

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