Some Examples of Phase-Transfer Catalysis Application in Organochlorine Chemistry

Abstract

Kinetics of phase-transfer catalysed (PTC'd) dehydrochlorination of the r-isomer of hexachlorocyclohexane in the presence of proton donors was investigated. Carboxylic acids and picric acid act as inhibitors. Benzyl alcohol strongly promotes the reaction. The plots of observed rate constants vs phenol and pentachlorophenol concentration have a bell-shaped form that was not observed before. An example of long-chain quats application in the synthesis of the ketamine anaesthetic intermediate by dehydrochlorination in dilute alkali is shown. Another application of phase-transfer catalysis (PTC) in organochlorine chemistry is the aqueous (sodium hypochlorite) chlorination of alkyl aromatic compounds. The results of m-phenoxytoluene chlorination and reaction kinetics in the presence of the polymeric crown are described.

Dechlorination of lindane in the multiphase catalytic reduction system with Pd/C, Pt/C and Raney-Ni

“…in a biphasic isooctane-aqueous KOH system, containing a heterogeneous catalyst (supported Pd, Pt, or Raney-Ni) and Aliquat 336, lindane may theoretically undergo two different dechlorination processes. Either base-assisted DHC, which is catalyzed by quaternary ammonium salts [9,10]; or catalytic HDC, also possible under these conditions in the presence of hydrogen. For this second process, as we have previously shown on the examples of polychlorinated aromatics [22][23][24][25][26], the presences of a base and of a quaternary salt are also necessary to achieve effective dechlorination.…”

“…As long ago as in 1871, Zinin reported on the reduction of HCH to benzene with metallic Zn in ethanol [6]. Lindane and its isomers can undergo the dehydrochlorination (DHC) reaction to form tricholorobenzenes (TCBs) either by thermal or the base-assisted processes [7][8][9][10]. The latter is more selective and can be carried out under mild conditions in the presence of a phase-transfer (PT) catalyst and an aqueous base [9,10].…”

“…Lindane and its isomers can undergo the dehydrochlorination (DHC) reaction to form tricholorobenzenes (TCBs) either by thermal or the base-assisted processes [7][8][9][10]. The latter is more selective and can be carried out under mild conditions in the presence of a phase-transfer (PT) catalyst and an aqueous base [9,10]. Electrochemical [11] and bacterial [11][12][13] processes of HCH or lindane degradation are known and afford benzene.…”

Removal of Organochlorine Compounds from Coal Tar by Nucleophilic Substitution and Coalescence

“…The procedures to remove oil-soluble OOCs from crude oil and coal tar include electrochemical method, catalysis, and adsorption, which have the limitations of high cost, complex operation, low adsorption capacity, and low selectivity [18][19][20][21][22]. On the other hand, the phase transfer nucleophilic method can be operated under ambient conditions and has the advantages of low cost, no secondary pollution, and good performance for OOCs removal [23][24][25][26][27][28].…”

Kinetics of ‘initial burst’ in the solid–liquid phase‐transfer catalysis. Nucleophilic substitution of 2‐octyl mesylate with potassium bromide

“…1 Occasionally, it has advantages over the common liquid-liquid (l/l) PTC and is sometimes successfully employed on an industrial scale. 2 There are a number of papers 3 which have reported on the kinetics and varied mechanistic questions, although there is still no unanimity regarding either the mechanism or the topology of s/l PTC.…”