Abstract: Kinetics of the electrophilic substitution reaction (1) of
CuCl_2+Cd(Ⅱ)P→Cu(Ⅱ)P+CdCl_2 (1)
cupric chloride with meso-tetrakis(meta-methylphenyl) porphyrin cadmium(Ⅱ) was studied by means of Shimadzu UV-240 spectrophotometer. The proposed mechanism is as follows:
Cd(Ⅱ)P+Cl~-<=>[Cd(Ⅱ)PCl]~- (2)
Cu(Ⅱ)+[Cd(Ⅱ)PCl]~-<=>[Cu(Ⅱ)PCl]~-+Cd(Ⅱ) (3)
[Cu(Ⅱ)PCl]~-→Cu(Ⅱ)P+Cl~- (4)
The experimental data were treated with AST-286 microcomputer. The equilibrim constant(K) of preequilibrium step(1) and the rate constants(k_1, k_(-1), k_2) of step (2) and step (3) were obtained. The standard molar enthalpy change △_rH_m~-θ-, and standard entropy change △_rS_m~-θ-, of step (1) and the activation parameters Δ~≠H_(m,1), Δ~≠H_(m,-1), Δ~≠H_(m,2) and Δ~≠S_(m,1), Δ~≠S_(m,-1), Δ~≠S_(m,2) were calculated.

Key words: Tetrakis (Meta-methylphenyl) Porphyrin Cadmium (II), Kinetics of Substitution reaction, Mechanism of reaction