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Photochemical radical chain dechlorination of DDT in isopropanol
186 Photochemical radical chain dechlorination of DDT in isopropanol
H.C.A.
VAN
EsEEK, H.J. VAN
DER
STOEP,
H. VAN
OORT
and J. VAN
LEENEN
Laboratory of Chemical Technology, Derft University of Technology, .Tulimmlaan136, 26228 BL Deift (The Netherlands)
DDT is dechlorinated to DDD by a radical chain process on anaerobic irradiation in isopropanol with 253.7 nm light. The quantum yield of this process is inversely proportional to the square root of the light intensity. The relation between the quantum yield and the optical density of the solution is determined by the nature of the termination reaction and the geometrical arrangement used in the experiments. The relations mentioned, which were derived from the reaction mechanism and the geometrical arrangements used, were confirmed by kinetic measurements. It was found that the reduction of the intermediate l,ldichloro-2,2-bis-@-chlorophenyl)ethyl radicals by isopropyl ketyl radicals and the disproportionation of the intermediate are the main termination reactions. The equations derived are useful for the design of photoreactors.
Vapour phase exciplex formation in cyano-substituted naphthalenes
G.D.
ABBOTT,
L. CHEWTER,
D.V.
O’CONNOR
and D. PHILLIPS
The Royal insti&ution,21 Alberrnarle Street, London WIX 4 BS (Gt. Britain)
Fluorescence was observed from vapour phase exciplexes in two systems: (1) electronically excited 1,4_dicyanonaphthalene and ground state 2,5-dimethyl2,4-hexadiene; (2) electronically excited l-cyanonaphthalene and ground state triethylamine. Decay times from both monomer and exciplex were measured using a synchronously pumped dye laser as an excitation source in the singlephoton counting technique. In system (1) the exciplex fluorescence intensity in weak monomer decay curves cannot be resolved satisfactorily into two components. Nevertheless, steady state results may be combined with transient measurements to yield thermodynamic properties. An exciplex binding energy of 8 kJ molW1 was calculated. The exciplex intensity in system (2) is relatively large and monomer decay curves are clearly double exponential with decay parameters that are in close agreement with exciplex fluorescence rise and decay times. The StemVolmer constant increases as the temperature decreases, as expected for the standard exciplex reaction scheme. Kinetic and thermodynamic data for this system are reported.
H.C.A.
VAN
EsEEK, H.J. VAN
DER
STOEP,
H. VAN
OORT
and J. VAN
LEENEN
Laboratory of Chemical Technology, Derft University of Technology, .Tulimmlaan136, 26228 BL Deift (The Netherlands)
DDT is dechlorinated to DDD by a radical chain process on anaerobic irradiation in isopropanol with 253.7 nm light. The quantum yield of this process is inversely proportional to the square root of the light intensity. The relation between the quantum yield and the optical density of the solution is determined by the nature of the termination reaction and the geometrical arrangement used in the experiments. The relations mentioned, which were derived from the reaction mechanism and the geometrical arrangements used, were confirmed by kinetic measurements. It was found that the reduction of the intermediate l,ldichloro-2,2-bis-@-chlorophenyl)ethyl radicals by isopropyl ketyl radicals and the disproportionation of the intermediate are the main termination reactions. The equations derived are useful for the design of photoreactors.
Vapour phase exciplex formation in cyano-substituted naphthalenes
G.D.
ABBOTT,
L. CHEWTER,
D.V.
O’CONNOR
and D. PHILLIPS
The Royal insti&ution,21 Alberrnarle Street, London WIX 4 BS (Gt. Britain)
Fluorescence was observed from vapour phase exciplexes in two systems: (1) electronically excited 1,4_dicyanonaphthalene and ground state 2,5-dimethyl2,4-hexadiene; (2) electronically excited l-cyanonaphthalene and ground state triethylamine. Decay times from both monomer and exciplex were measured using a synchronously pumped dye laser as an excitation source in the singlephoton counting technique. In system (1) the exciplex fluorescence intensity in weak monomer decay curves cannot be resolved satisfactorily into two components. Nevertheless, steady state results may be combined with transient measurements to yield thermodynamic properties. An exciplex binding energy of 8 kJ molW1 was calculated. The exciplex intensity in system (2) is relatively large and monomer decay curves are clearly double exponential with decay parameters that are in close agreement with exciplex fluorescence rise and decay times. The StemVolmer constant increases as the temperature decreases, as expected for the standard exciplex reaction scheme. Kinetic and thermodynamic data for this system are reported.