ISSN:
0538-8066
Keywords:
Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Kinetic solvent isotope effects (KSIE) were measured for the hydrolyses of acetals of benzaldehydes in aqueous solutions covering the pH (pD) range of 1-6. For p-methoxybenzaldehyde diethyl acetal, kD+/kH+ = 1.8-3.1, depending on the procedure used to calculate the KSIE and on the pH (pD) range used as the basis for kH+(kD+). It is shown that this variation is an experimental artifact, and is a characteristic of KSIE measurements in general. It is recommended that kL+ be calculated from a least-squares fit of data to the equation kobs = kL+[L+], and that the KSIE be reported as kD+/kH+. The limitation remains, however, that the KSIE measured for a variety of substances over quite different pH (pD) ranges may not be comparable to more than ℜ20%. The source of these observations is discussed in terms of small changes in the activity coefficient ratios (a specific salt effect), including the solvent isotope effect on the activity coefficient ratio [eq. (3)].
Additional Material:
7 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/kin.550150304
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