Influence of Substituents on Reactivity and Reaction Mechanism of SN Reaction of Some Organophosphorus Compounds; Relied on Linear Free Energy Relationship.

The tetracoordinated organophosphorous compound (4 - Chlorophenyl 4 - methyl phenyl Chlorophosphate, 1) were synthesized, characterized and nucleophilic substitution reaction (pyridinolysis) were investigated in acetonitrile at 5.0 o C by varying substituents in nucleophiles. The reactivity is expressed in terms of second-order rate constant, k 2 and measured conductometrically. Physical organic chemistry tools mainly Hammett (ρ), Brönsted (β) Linear Free Energy Relationship (LFER) coefficients being determined in quest for the mechanistic information by comparing pyridinolysis of structurally similar organophosphorous compounds reported earlier. Nice linear correlation being found for Hammett (logk 2 vs σx) and Brönsted (logk 2 vs pK a(x) ) plots. In the light of the reported results the LFER obtained for 1 with negative value of the ρ X , −5.78 and large positive value for β X , 1.17 can be interpreted as S N 2 process, with greater extent of bond formation in TS of 1. [ABSTRACT FROM AUTHOR]