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Basicity of some aliphatic amines in mixed H 2 OCH 3 CN solvents
Author(s) -
Khan M. Niyaz,
Arifin Z.,
George A.,
Wahab I. A.
Publication year - 2000
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/(sici)1097-4601(2000)32:3<146::aid-kin4>3.0.co;2-r
Subject(s) - chemistry , acetonitrile , amine gas treating , aqueous solution , solvent , conjugate acid , solvent effects , base (topology) , phenol , organic chemistry , ion , mathematical analysis , mathematics
The values of p K a ms ( K a ms represents ionization constant of conjugate acid of amine base in mixed water–acetonitrile solvent) for all amines, except for charged amine bases, show a mild decrease (ca. 0.1–0.4 p K units) with the increase in CH 3 CN content from 2 to ∼60% v/v. However, the p K a ms values at 70% v/v CH 3 CN become nearly equal or slightly larger (by ≤0.7 p K units) than the corresponding p K a ms at 2% v/v CH 3 CN for all neutral and charged amines. The values of p K a ms for phenol increase from 10.17 to 13.38 with the increase in the content of CH 3 CN from 2 to 70% v/v in mixed aqueous solvent. Taft reaction constants, ρ*, obtained from the plots of p K a ms against ∑σ* for primary and secondary amines decrease by ca. 0.8 ρ* units with the increase in the CH 3 CN content from 2 to 70% v/v. The values of p K a ms show an empirical linear relationship with the corresponding values of p K a w (where p K a w represents the p K a obtained in aqueous solvent containing 2% v/v CH 3 CN), which allows the estimation of a p K a in mixed H 2 OCH 3 CN solvents from that in water. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 146–152, 2000