RATES OF DEDIAZONIATIONS OF ARENEDIAZONIUM IONS COMPLEXED WITH 18-, 21- AND 24-MEMBRED CROWN ETHERS
The evaluation of the kinetics of dediazoniation of benzenediazonium tetrafluoroborate and p-chlorobenzenediazonium tetrafluoroborate in 1,2-dichloroethane at 50 deg C in the presence of 18-crown-6, 21-crown-7 and dicyclohexano-24-crown-8 demonstrates that the rate constant for the dediazoniation within the complex is smallest, and the equilibrium constant for complex formation is largest for the complex with 21-crown-7.
Nakazumi, Hiroyuki,Szele, Ivanka,Zollinger, Heinrich
Influence of Steric and Electronic Effects on the Binding of Arenediazonium Cations to 18-Crown-6 in Methanol at 25 deg C
Log K, ΔH, and TΔS values for the interaction of several arenediazonium salts with 18-crown-6 were determined in methanol at 25 deg C by the calorimetric titration technique.The complex of benzenediazonium cation with 18-crown-6 is enthalpy stabilized with log K = 2.50.Substitution of a methyl group onto the ortho position(s) of benzenediazonium cation results in a total loss of complex stability.Substitution of various groups onto the para position results in changes in complex stability according to the electronic effect exerted in the diazonium moiety.A linear Hammett relationship (ρ = 0.65) was found between log K and ?+p values associated with the para substituent.
Izatt, R. M.,Lamb, J. D.,Swain, C. S.,Christensen, J. J.,Haymore, Barry L.
p. 3032 - 3034
(2007/10/02)
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