TRANSFER FREE-ENERGIES OF TRIMETHYLAMMONIUM HYDROCHLORIDE-A PRECURSORTO A POTENTIAL MODEL TRANSITION-STATE FOR SN1-TYPE HYDROLYSIS OF TERT-BUTYL CHLORIDE IN SOME AQUO-ORGANIC SOLVENTS
M. Datta et Kk. Kundu, TRANSFER FREE-ENERGIES OF TRIMETHYLAMMONIUM HYDROCHLORIDE-A PRECURSORTO A POTENTIAL MODEL TRANSITION-STATE FOR SN1-TYPE HYDROLYSIS OF TERT-BUTYL CHLORIDE IN SOME AQUO-ORGANIC SOLVENTS, Indian journal of chemistry. Sect. A: Inorganic, physical, theoretical & analytical, 32(6), 1993, pp. 478-484
Transfer free energies, DELTAG(t)0, of trimethylammonium hydrochloride
(Me3NHCl)-a precursor to a potential model for the transition state (
TS) for S(N)1-type hydrolysis of tert-butylchloride (t-BuCl), have bee
n determined in aqueous mixtures of various organic cosolvents viz pro
tic tert-butanol (t-BuOH), ethylene glycol (EG), glycerol (GL) and met
hoxyethanol (ME), aprotic dimethoxyethane (DMSO) and dioxane (D) and d
ipolar aprotic 1,2-dimethylformamide (DMF) and dimethyl sulphoxide (DM
SO). These have been determined by measuring the solubilities of spari
ngly soluble salt Me3NHBPh, (Ph=phenyl) at 25-degrees-C in the solvent
s and by using the relation: DELTAG(t)0 (Me3NHCl) = DELTAG(T)0(Me3NHBP
h4) - DELTA G(t)0 (Ph4B-) + DELTAG(t)0 (CI-). The required individual
ion contributions for the solvents, based on widely used Ph4AsPh4B (TB
TB) reference electrolyte (RE) assumption, have been taken from previo
us studies. The chemical contributions of DELTAG(t)0(i) values of Me3N
H+ and Cl- have been obtained after subtracting the respective contrib
utions of cavity, Born and ion-dipole interactions, as computed by sca
led particle theory (SPT), Born and Buckingham formulations respective
ly and are referred to as DELTAG(T,H1H)0(Cl-) and DELTAG(t,HbH)0(Me3NH
+). This is because while DELTAG(t,H.1H)0(Cl-1) values are guided by h
ydrophilic hydration (H1H) effect arising chiefly from the relative pr
oticity/aproticity of the respective cosolvents, DELTAG(t,HbH)0 H(Me3N
H+) values are guided by hydrophobic hydration (H(b)H) effect arising
chiefly from the hydrophobic propensity of Me3NH+, apart from the disp
ersion, relative basicity and structural interaction effect of the cos
olvents.