Transfer energetics of tetraalkylammonium picrates in an aqueous ionic cosolvent system and the salt effect on hydrophobic hydration

Salt effects on the reactivity of the base‐catalyzed hydrolysis of some novel low‐spin hydrophobic Fe(II)–amino acid azomethine chelates

“…In the presence of higher concentrations (≥3.3 × 10 −3 mol dm −3 ) of TBAB, the rate constants decrease with increasing the added salt. This inversion in the reactivity trend assumes, as reported previously 19, 20, the formation of the cyclic quadrupole interaction between the salt ion pair and the solvent as shown below: Thus, this cyclic quadrupole enhances Lewis acidity of hydrogen atoms on water, leading to more stabilization of OH − by hydrogen bonding to water hydrogens. This effect retards the attack of OH − ions on the intermediate complex, in the transition state step, and consequently reduces the reactivity.…”

“…This inversion in the reactivity trend assumes, as reported previously [19,20], the formation of the cyclic quadrupole interaction between the salt ion pair and the solvent as shown below:…”

“…This behaviour can be explained as due to the rupture of the hydrogen bonds between water molecules and expansion of the voids between such molecules. This enhances the formation of larger linear quadrupoles, referred to above, and thus increases the reactivity, particularly in dilute solutions of the salt (TBAB) [19][20][21].…”

“…The subsequent decrease in the reactivity by higher [TBAB] can be attributed to the dominating desolvation effect of the hydrophobic TBAB cation on OH − ions (hydrophilic) by its characteristic hydrophobic hydration 18 and the extensive solvation of the less hydrophobic smi complex. Again TBAB, in low concentrations, forms linear quadrupole B 2− Bu 4 N + OH − Na + by the nucleophilic catalysis of the charge separation that expands the voids of hydrogen‐bonded H 2 O molecules 19, 20. This behaviour of TBAB, in the aqueous medium, enhances the probability of the reaction between the intermediate complex (B 2− ) with OH − ions, because the bulky Bu 4 N + , in that ion pair, caves the reacting anions and thus facilitates their reaction.…”

A systematic modelling framework for phase transfer catalyst systems

“…We have applied the NRTL-SAC to subsystem C and the eNRTL-SAC to subsystem D. Since segment numbers are not known for tetraalkylammonium PTC in Subsystem C, we have regressed the parameters to experimental data from Yu and Friedman (1966), Frank and Clarke (1967), Abraham and co-workers (1970;1972;1973;1983;, Talukdar and Kundu (1991), and Lee and Huang (2002). In total, 63 binary systems in 12 organic solvents, with 65 experimental points were used.…”