146
A. V. BURASOV ET AL.
accurate value for r and C, the software iterates through
values of D and n, until the fit of the experimental data had
been optimized.
in CDCl3 and referenced to tetramethylsilane (SiMe4),
as an internal standard. Signal positions were recorded in
d (ppm) with the abbreviations s, d, t, q, quint., sept., br,
app., and m denoting singlet, doublet, triplet, quartet,
quintet, septet, broad, apparent, and multiplet, respect-
ively. All coupling constants, J, are quoted in Hz.
Crude electrolysis mixture was analyzed by thin-layer
chromatography (TLC). TLC was performed on Merck
Kieselgel 60 F254 0.25 mm pre-coated aluminum backed
silica plates. Compounds were visualized with UV light and/
or by staining with basic potassium permanganate solution.
Flash chromatography was used to separate the
products, following electrolysis and carried out, accord-
ing to the method described by Still et al. 23 using Merck
Kieselgel 60 (40–63 mm). Column fractions were
monitored by TLC.
Preparative electrolysis. Controlled-potential, bulk
electrolysis was carried out in a two-compartment cell,
the catholyte and anolyte being separated by a sintered
glass frit. The cathode was a rectangular platinum
plate (area ¼ 3.25 cm2) (Goodfellow, UK) and the anode,
a platinum mesh housed within the separate compartment
with 0.1 M TBAP in THF. A Fc/FcRPF6S reference
electrode was used as described above. The electrolysis
was vigorously stirred, using a magnetic stirrer bar and
the temperature maintained at 195 ꢁ 1 K, using an
external system (Julabo FT902, JULABO Labortechnik
GmbH, D-77960 Seelbach/Germany). The potential was
held constant at the reduction potential of naphthalene
(vs. Fc/FcRPFS6 ). Naphthalene was added to the solution
at 195 ꢁ 1 K to minimize any decomposition of the
mediator.
RESULTS AND DISCUSSION
Saturated aqueous ammonium chloride (2 mL)
followed by water (10 mL) was added to the electrolyzed
solution upon reaction completion. Diethyl ether (20 mL)
was then added and the two fractions separated. The
organic fraction was then washed with aqueous hydro-
chloric acid (1 M 6 T10 mL), saturated sodium bicarbonate
(10 mL), and saturated aqueous sodium chloride (10 mL).
The organic layer was dried over magnesium sulfate and
then evaporated under reduced pressure. Products were
initially identified by 1H NMR (Bruker AV400 (400 MHz)
spectrometer) and then separated using TLC/flash chroma-
tography (petrol:diethyl ether elutions). Yields for isolated
RH and PhSSPh were 7.1 mg (19%) and 3.5 mg (4%),
respectively. Analytical data for these compounds were
identical to literature data and are given below.
Voltammetric studies of starting compounds:
naphthalene and RSPh
A 6.5 mM solution of naphthalene in THF was prepared
and cooled to 201 ꢁ 1 K. A platinum microelectrode was
used to record a voltammetric response, and a reduction
wave with a well-defineþd plateau was observed at
E ¼ ꢀ3.11 V versus Fc/Fc PFꢀ6 reference electrode, as
shown in Fig. 2. The number of electrons transferred
in the reduction, n and the diffusion coefficient, D of
naphthalene were obtained using microdisk potential
step chronoamperometry.7,24 Figure 3 depicts a typical
chronoamperometric curve with the corresponding fitting
applied to deduce the required parameters. Experiments
were repeated a number of times and the average D and n
trans-1-(Methoxymethoxy)-4-propoxycyclohexane
(RH)7. 1H NMR (400 MHz, CDCl3): dH ¼ 4.66 (2H,
s, OCH2OCH3), 3.43 (1H, m, cyclohexane CH), 3.38
(2H, t, J 6.8, OCH2), 3.36 (3H, s, OCH2OCH3), 3.25
(1H, m, cyclohexane CH), 1.99 (4H, m, cyclohexane CH2),
1.57 (2H, m, OCH2CH2), 1.33 (4H, m, cyclohexane CH2),
0.90 (3H, t, J 7.4, CH3); 13C NMR (100 MHz, CDCl3):
dC ¼ 94.7, 76.5, 74.6, 70.1, 55.2, 30.0, 29.5, 23.3, 10.6; MS
(CIþ): m/z 220 (40%, [M þ NH4]þ), 203 (15%, [M þ H]þ);
HRMS C11H23O3 (MH) requires 203.1647, MHþ found
203.1656 (þ4.5 ppm); IR (film) per cmꢀ1: nmax ¼ 2937,
1455, 1377, 1106, 1045.
1
Diphenyl disulfide (PhSSPh)22. H NMR (200 MHz,
CDCl3): dH ¼ 7.19–7.36 (m, 6H), 7.48–7.53 (m, 4H);
13C NMR (100 MHz, CDCl3): dC ¼ 127.1, 127.5, 129.0,
.
137.0, MS (%B): m/z 218 (M þ, 100), 185 (M-SH, 13),
.
154 (C12H1þ0 , 32þ), 109 (C6H5Sþ, 64); IR (KBr):
n ¼ 1573, 1473, 1436, 736, 686 cmꢀ1
.
Figure 2. Voltammetric response of naphthalene (6.5 mM)
in THF (0.1 M TBAP), using a 5 mm (radius) plꢀa1tinum micro-
electrode recorded at a scan rate of 10 mV s
1
Analytical techniques. H NMR spectra were
recorded using a Bruker AV400 (400 MHz) spectrometer
Copyright # 2007 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2007; 20: 144–150
DOI: 10.1002/poc