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PicOMes was injected by a gas-tight syringe (200 µL; final
concentrations 0.06–0.09 M). The final mixture was placed in
a dry ice – acetone bath that had been maintained at –50°C.
The contents of the tube were allowed to mingle at this tem-
perature. The tube was inverted several times to promote
mixing and was then immersed again in liquid N2. The tube
was transferred to the spectrometer probe (at –40°C), the in-
strument was tuned as previously described (6b), and spectra
were recorded at various intervals. A standard collection of
FID would be made at 3, 5, 7, and 9 min and then as war-
ranted by observed changes in the spectrum. Simulta-
neously, the temperature of the probe was gradually raised.
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Room temperature experiments in DMSO
A solution of the substrate was prepared in DMSO-d6 un-
der an N2 atmosphere. An aliquot of this solution was trans-
ferred via syringe into an NMR tube and an initial spectrum
run to ascertain the purity of the substrate. To this solution
1 equiv of nucleophile was injected through the septum and
spectra were recorded as rapidly as possible initially and
then at longer times as the reaction proceeded. 1,4-Dibromo-
benzene was present in the solution of the substrate and in
the NMR tube as an internal integration standard.
Molecular orbital calculations
Semi-empirical calculations were performed using
AMPAC version 2.10 of AM1 (15a) on an IBM 3081 com-
puter. The structure of 2,4,6-trinitroanisole (TNA) was cal-
culated using the PRECISE option within the restricted
Hartree–Fock (RHF; closed shell) scheme. The TNA struc-
ture was fully optimized following a Fletcher–Powell
minimization (40) to a self-consistent field (SCF) that satis-
fied Herbert’s test. The final structure was characterized as a
local minimum when no negative force constants were ob-
tained using the FORCE option.
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Acknowledgments
This research has been financed by a number of agencies.
The support of the Natural Sciences and Engineering Re-
search Council of Canada (NSERC) (to E.B.) and Wake For-
est University (to R.A.M.) as well as the award of an R.T.
Mohan Fellowship (to R.M.T.) is gratefully acknowledged.
Discussions with Professors S. Hoz and F. Terrier were help-
ful, as always, and are appreciated.
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