Res. Chem. Intermed.
, Vol. 28, No. 1, pp. 71 –78 (2002)
ESR studies on solvation by using s-butyl tri uoroacetyl
, YI-YUAN PENG
and CHENG-XUE ZHAO
Department of Chemistry, Shanghai Jiaotong University, Shanghai 200240, China
Department of Chemistry, Jiangxi Normal University, Nanchang 330027, China
Received 10 August 2001; accepted 11 October 2001
Abstract—Stable s-butyl tri uoroacetyl nitroxide (3) has been generated in electron-transferreaction
of O-benzoyl-N-s-butylhydroxylamine (1) and tri uoroacetyl peroxide (2) in F113 (CFCl
solution at room temperature. ESR measurement of a
values for 3 in 21 solvents has been
carried out at 24
C. The a
values for 3 in 12 aprotic solvents show a linear correlation with the
cybotactic solvent parameters E
and Z, i.e. a
The physical signi cance for the slopes, slope
Z, the extrapolated intercepts on the
axis are linked to the sensitivity of the nitroxide toward the solvation, the magnitude of the overall
solvaton effect on the a
values, and the intrinsic a
value of 3 in the ideal gaseous state, respectively.
The plots of a
noncybotactic solvent constants, such as dipolar moment (¹) and dielectric
constant ("), all show random cases.
: ESR; s-butyl tri uoroacetyl nitroxide; solvation.
The solvent dependency of
factors and line widths are well established
for some bulky and stable di-t-alkyl nitroxides such as di-
-butyl nitroxide and
TEMPO . In the last fteen years, a large number of uorinated nitroxides with
a wide variety of structures have been generated and subjected to extensive studies
in our laboratories . Some nitroxides like
-butyl per uoroalkyl (
) nitroxides, much less hindered, with no
-H atom and expected to be
subjected to extra-stabilization due to capto –dative effect , have been employed
as spin probes in the ESR studies on the nature of solvation . Now, we wish to
expand our studies on solvation by using a new type of spin probe, a uorinated acyl
, with much higher spin density on nitroxyl N atom.
To whom correspondence should be addressed.