Journal of Organic Chemistry p. 705 - 710 (1980)
Update date:2022-08-11
Topics:
Nome, Faruk
Schwingel, Erineu W.
Ionescu, Lavinel G.
The base-catalyzed oxidative cleavage of 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethanol (Dicofol) results in the formation of chloroform and 4,4'-dichlorobenzophenone.The reaction was studied in the presence of hexadecyltrimethylammonium bromide (CTAB) and hexadecyldimethyl(2-hydroxyethyl)ammonium bromide (CHEDAB), and catalytic factors of 200- and 345-fold, respectively, were obtained.The experimental results are rationalized in terms of an increase of the concentration of the reagents in the micellar phase.Sodium dodecyl sulfate (NaLS) inhibits the reaction, and dodecylcarnitine chloride (LCC) essentially does not alter the rate.The catalysis by cationic surfactants (CTAB, CHEDAB) is inhibited by added salts.The effectiveness of the salts in decreasing the rate constant is NaCl < NaBr < NaNO3 < Na2SO4 < NaOTs.The activation parameters for 4.0E-3 M CTAB (ΔH(excit.) = 27.7 kcal/mol, ΔG(excit.) = 19.8 kcal/mol, ΔS(excit.) = 25.9 eu) and for 1.0E-1 M CTAB (ΔH(excit.) = 26.7 kcal/mol, ΔG(excit.) = 20.8 kcal/mol, ΔS(excit.) = 19.6 eu) indicate that the rate decrease observed at high surfactant concentration is due to an entropic contribution to the free-energy term.
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