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Basicity of some aliphatic amines in mixed H2OCH3CN solvents

✍ Scribed by M. Niyaz Khan; Z. Arifin; A. George; I. A. Wahab

Publisher
John Wiley and Sons
Year
2000
Tongue
English
Weight
100 KB
Volume
32
Category
Article
ISSN
0538-8066

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✦ Synopsis

The values of pK a ms (K a ms represents ionization constant of conjugate acid of amine base in mixed waterϪacetonitrile solvent) for all amines, except for charged amine bases, show a mild decrease (ca. 0.1-0.4 pK units) with the increase in CH 3 CN content from 2 to ϳ60% v/v. However, the pK a ms values at 70% v/v CH 3 CN become nearly equal or slightly larger (by Յ0.7 pK units) than the corresponding pK a ms at 2% v/v CH 3 CN for all neutral and charged amines. The values of pK 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, *, obtained from the plots of pK a ms against ͚* for primary and secondary amines decrease by ca. 0.8 * units with the increase in the CH 3 CN content from 2 to 70% v/v. The values of pK a ms show an empirical linear relationship with the corresponding values of pK a w (where pK a w represents the pK a obtained in aqueous solvent containing 2% v/v CH 3 CN), which allows the estimation of a pK a in mixed H 2 O-CH 3 CN solvents from that in water.

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