atmospheric pressure and the residual thiol was distilled under
reduced pressure from a small amount of LiAlD4 to give a
colourless oil (bp 134–136 ЊC, 10 mmHg). H-NMR spectro-
and fitted with a condenser through which a very slow down-
ward flow of argon was maintained. The side arm was closed
with a self-sealing silicone rubber septum and the flask was
immersed in a thermostatically-controlled oil bath pre-heated
to 60 ЊC. The mixture was stirred for 5 min to allow thermal
equilibration to take place, before a 0.25 M solution of TBHN
in cyclohexane (160 µl, 0.04 mmol) was added to the mixture via
the septum; this addition defined t = 0. Samples of the reaction
mixture (10 µl) were removed at 3 min intervals and quenched
by dilution with ice-cold dry hexane (100 µl) in a small sample
tube closed with a septum. These solutions were then analysed
by GLC to give the results listed in Table 5.
1
scopic analysis showed that the S-deuteriated dodecane-1-thiol
contained ca. 96 atom% D by comparison of the C11H23CH2SD
3
3
resonance (δH 2.41, tt, JHH 7.1, JHD 1.1) with the C11H23-
CH2SH resonance (δH 2.42, apparent q, <3JHH> 7.3).
S-Deuteriated tri-tert-butoxysilanethiol and triisopropyl-
silanethiol were prepared by the same method and were shown
to contain ca. 98% and 96% atom% D, respectively, by inte-
gration of the residual SiSH singlets at δ Ϫ0.01 and δ Ϫ0.77,
respectively, against other peaks in the spectra. Bearing in mind
the sensitivity to hydrolysis of Ph3SiSH, the relative stability of
(ButO)3SiSH/D and Pri3SiSH/D towards D2O at ca. 80 ЊC is
remarkable.
Acknowledgements
We are very grateful to Dr Abil Aliev for his help in using NMR
spectroscopy to monitor the H/D exchange processes and we
acknowledge support for this work from the EPSRC.
Representative procedure for reduction of octyl halides
The response of the flame-ionisation detector was calibrated
using mixtures of known amounts of authentic compounds
and nonane as reference.
References
Admantane-1-thiol (8.4 mg, 0.05 mmol), triethylsilane
(116 mg, 1.0 mmol), bromo-1-octane (147 mg, 0.76 mmol),
nonane (90 µl, added using a calibrated microsyringe) were suc-
cessively introduced into an argon-filled 10 cm3 two-necked
round-bottomed flask, containing a dry magnetic stirrer bar,
and fitted with a condenser through which a very slow down-
ward flow of argon was maintained. Cyclohexane (1.42 cm3)
was then added so that, after addition of the initiator, the total
volume of the reaction mixture would be 2.00 cm3 (assuming
ideal mixing and neglecting thermal expansion of the solution).
The side arm was closed with a self-sealing silicone rubber sep-
tum (Aldrich) and the flask was immersed in a thermostatically-
controlled oil bath pre-heated to 60 ЊC. The mixture was stirred
for 5 min to allow thermal equilibration to take place, before a
0.25 M solution of TBHN in cyclohexane (200 µl, 0.05 mmol)
was added to the mixture via the septum; this addition defined
t = 0. Samples of the reaction mixture (10 µl) were removed at
3–5 min intervals and quenched by dilution with ice-cold dry
hexane (100 µl) in a small sample tube closed with a septum.
These solutions were then analysed by GLC to give the results
listed in Table 1.
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Representative procedure for H/D exchange experiments
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V. Barone, M. Cossi, R. Cammi, B. Mennucci, C. Pomelli,
C. Adamo, S. Clifford, J. Ochterski, G. A. Petersson, P. Y.
Ayala, Q. Cui, K. Morokuma, D. K. Malick, A. D. Rabuck,
K. Raghavachari, J. B. Foresman, J. Cioslowski, J. V. Ortiz,
B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi,
R. Gomperts, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham,
C. Y. Peng, A. Nanayakkara, C. Gonzalez, M. Challacombe,
Triphenylsilanethiol (ca. 12.3 mg, 0.042 mmol), Et3SiD
(ca. 36.6 mg, 0.312 mmol), hexamethyldisiloxane (ca. 5 µl) and
TBHN (ca. 42.5 µl of a 0.20 M solution in cyclohexane-d12,
0.0085 mmol) were successively introduced at room tempera-
ture into a dry, argon-filled NMR tube closed with a self-sealing
rubber cap. Cyclohexane-d12 (ca. 550 µl) was then added to
make the total volume up to a 650 µl calibration mark on the
NMR tube. The rubber cap was replaced with a dry standard
polypropylene cap, the solution was mixed thoroughly by shak-
ing and an NMR spectrum was recorded at 25 ЊC, allowing the
initial concentrations of the reagents to be determined accur-
ately by integration of appropriate peaks using the silane as the
primary standard. The probe temperature was then increased to
50 ЊC, without removing the sample from the spectrometer in
order to reduce the time needed for re-shimming; we estimate
that the sample temperature would reach 50 ЊC within 2–3 min.
The progress of the reaction was then monitored every minute
and the results are given in Table 4. Similar experiments at 40–
60 ЊC were also used to determine the effective rate of initiation
by thermal decomposition of TBHN (see Results section).
Representative procedure for racemisation of (S )-ButMePhSiH
Admantane-1-thiol (6.7 mg, 0.040 mmol), (S )-ButMePhSiH
(142 mg, 167 µl, 0.80 mmol) and cyclohexane (1.67 cm3) were
successively introduced into an argon-filled 10 cm3 two-necked
round-bottomed flask, containing a dry magnetic stirrer bar,
J. Chem. Soc., Perkin Trans. 2, 2002, 1858–1868
1867