A comparative study on the reactivity of electrogenerated bromine with cyclohexene in acetonitrile and the room temperature ionic liquid, 1-Butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide

Article abstract of DOI:10.1021/jp040400z

The reactivity of electrogenerated bromine with cyclohexene has been studied on a platinum microelectrode by linear sweep and cyclic voltammetry in both the room temperature ionic liquid, 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, an

Full text of DOI:10.1021/jp040400z

16322
J. Phys. Chem. B 2004, 108, 16322-16327
A Comparative Study on the Reactivity of Electrogenerated Bromine with Cyclohexene in
Acetonitrile and the Room Temperature Ionic Liquid, 1-Butyl-3-methylimidazolium
Bis[(trifluoromethyl)sulfonyl]imide
Gary D. Allen,† Marisa C. Buzzeo,† Ieuan G. Davies,‡ Constanza Villagra´n,§
Christopher Hardacre,§ and Richard G. Compton*,†
Physical and Theoretical Chemistry Laboratory, UniVersity of Oxford, South Parks Road,
Oxford, OX1 3QZ, United Kingdom, Central Chemistry Research Laboratory, UniVersity of Oxford,
Mansfield Road, Oxford, OX1 3TA, United Kingdom, and School of Chemistry/QUILL,
Queen’s UniVersity Belfast, Belfast, Northern Ireland, BT9 5AG, United Kingdom
ReceiVed: May 31, 2004; In Final Form: August 5, 2004
The reactivity of electrogenerated bromine with cyclohexene has been studied on a platinum microelectrode
by linear sweep and cyclic voltammetry in both the room temperature ionic liquid, 1-butyl-3-methylimidazolium
bis[(trifluoromethyl)sulfonyl]imide, and the conventional aprotic solvent, acetonitrile. Variation in the
voltammetric response was observed in the two solvents, indicating that the bromination reaction proceeded
via separate mechanisms. To identify the different products, electrolysis was conducted on the preparative
scale and NMR spectroscopy confirmed that while bromination of the organic substrate in the ionic liquid
yields trans-1,2-dibromocyclohexane, in acetonitrile, trans-1-(N-acetylamino)-2-bromocyclohexane is instead
obtained as the major product. The reaction mechanism for bromination in acetonitrile has been modeled
using digital simulation.
1. Introduction
as electrochemical solvents. The viscosities of ionic liquids are
typically at least an order of magnitude greater than conventional
solvents and thus the rate of mass transport is significantly
slower in the former. This has a direct effect on the diffusion
of species within RTILs and has been shown to result in
interesting voltammetric behavior.22,23
The voltammetry of bromide has been investigated in
traditional aprotic solvents over the past fifty years.1-4 Most
investigations have been performed in acetonitrile, where both
the tribromide anion, Br3-, and molecular bromine, Br2, are
reportedly generated upon oxidation. The bromination of
multiple bonds via electrophillic addition and substitution are
well-known reactions and the reactivity of electrogenerated
bromine species with a number of organic substrates, including
xylene, styrene, phenol, and cyclohexene has been reported in
conventional solvents.5-14
Herein we report the oxidation of bromide in the room-
temperature ionic liquid, 1-butyl-3-methylimidazolium bis-
[(trifluoromethyl)sulfonyl]imide ([C4mim][N(Tf)2]) and aceto-
nitrile (MeCN). The subsequent reactivity of the electrogenerated
bromine species with cyclohexene is investigated in both
solvents and the individual voltammetric responses compared
and contrasted. Bulk electrolysis was performed to confirm the
products of this reaction, which vary primarily as a result of
the differing nucleophilicities of the two solvents.
Room temperature ionic liquids (RTILs) are compounds
composed entirely of ions and exist in the liquid state around
298 K and below. They offer numerous advantages as solvents
in electrochemistry, including high thermal stability, low
volatility, wide potential windows, and finally, good conductiv-
ity, which negates the need for added electrolyte, a prerequisite
in the traditional solvent matrix.15-21 Other properties of RTILs
must be considered carefully, however, when they are employed
Although our studies were primarily aimed at investigating
the voltammetric response of bromide and cyclohexene, our
positive results suggest that such reactions in ionic liquids could
potentially be applied to large-scale organic synthesis. Signifi-
cant consideration would have to be given to reaction conditions
and product extraction techniques, but the recyclability of RTILs
and the reduced waste as compared to traditional solvent systems
where added electrolyte is generally unrecovered merits them
attractive alternatives. In the past decade, various examples of
electrosynthesis conducted in ionic liquids have appeared in the
literature, including the electrocyclic addition of carbon dioxide
to epoxides, the activation of molecular oxygen in the presence
of a Mn(III) catalyst and the reduction of alkyl and benzyl
halides, resulting in the direct formation of a carbon-carbon
bond.24-26 Additionally, a number of polymerization reactions
in ionic liquids have also been documented.27-29 This, however,
is the first report of the electrochemical bromination of an alkene
in an ionic liquid.
2. Experimental Section
2.1. Chemical Reagents. 1-Butyl-3-methylimidazolium bis-
[(trifluoromethyl)sulfonyl]imide ([C4mim][N(Tf)2]) was syn-
thesized from the corresponding halide salt via a metathesis
reaction in aqueous lithium bis[(trifluoromethyl)sulfonyl]imide,
as described by Bonhoˆte et al.16 1-Ethyl-3-methylimidazolium
bromide ([C2mim]Br) was prepared by the reaction of 1-methyl-
imidazole (Aldrich) and ethyl bromide (Aldrich) in MeCN at
* To whom correspondence should be addressed. Tel: 01865 275413.
Fax: 01865 275410. E-mail: richard.compton@chemistry.ox.ac.uk.
† Physical and Theoretical Chemistry Laboratory, University of Oxford.
‡ Central Chemistry Research Laboratory, University of Oxford.
§ Queen’s University Belfast.
10.1021/jp040400z CCC: $27.50 © 2004 American Chemical Society
Published on Web 09/21/2004

Reactivity of Electrogenerated Br with Cyclohexene
J. Phys. Chem. B, Vol. 108, No. 41, 2004 16323
∼80 °C. 1-Methylimidazole and ethyl bromide were purified
by distillation under reduced pressure prior to use. [C2mim]Br
was purified by recrystallization from its MeCN solution by
addition of ethyl acetate (Riedel-de-Hae¨n) several times under
a dry nitrogen atmosphere and then dried under vacuum.
Acetonitrile (MeCN, Fisher Scientific), cyclohexane (Fisher),
cyclohexene (Fisher), trans-1,2-dibromocyclohexane (Aldrich),
ferrocene (Aldrich), lithium bromide (LiBr, Aldrich), lithium
perchlorate (LiClO4, Fluka), phenol (Aldrich), styrene (Aldrich),
and tetrabutylammonium perchlorate (TBAP, Fluka) were used
directly without further purification.
2.2. Electrodes. The 10 µm diameter platinum (Pt) microdisk
working electrode (Cypress Systems) was carefully polished
before each experiment using a 1.0 µm alumina slurry (Buehler,
Lake Bluff, IL), followed by a 0.3 µm alumina suspension
(Buehler). The electrode was then polished on a clean, damp
cloth (Microcloth, Buehler), immersed in 10% nitric acid
solution to remove any adventitious adsorbates, and then rinsed
with MeCN. The diameter of the microdisk electrode was
calibrated electrochemically using 2 mM ferrocene in 0.1 M
TBAP/MeCN, assuming a value for the diffusion coefficient
of 2.3 × 10-9 m2 s-1 at 20 °C.30 The Pt rotating disk electrode
(7 mm diameter) was polished in a similar manner using 6 µm
diamond spray (Kemet International Ltd., Kent, U.K.).
stirred continuously while the potential was held on the plateau
of the second oxidative wave for 10 and 24 h in 0.1 M LiClO4/
MeCN (50 mL, E ) 1.8 V) and [C4mim][N(Tf)2] (10 mL, E )
1.8 V), respectively, or until the desired charge had been passed.
A white powder accumulated on the counter electrode during
the course of the electrolysis. These experimental conditions
were not optimized; current efficiencies are therefore not
reported. Acetonitrile was removed on a rotary evaporator and
NMR spectra were obtained on the resulting residue. The
product was extracted from the ionic liquid with three successive
cyclohexane washes (3 × 10 mL), which were combined and
washed with a saturated brine solution (30 mL) to remove any
residual [C4mim][N(Tf)2]. The cyclohexane was then removed
on a rotary evaporator and the residue analyzed by NMR. The
following spectra were obtained. 1H and 13C NMR: (C6H10Br2)
δH (400 MHz, CDCl3), 1.50 (2H, m, CH2CH2CHBr), 1.78 (2H,
m, CH’2CH2CHBr), 1.90 (2H, m, CH2CHBr), 2.49 (2H, m,
CH’2CHBr), 4.45 (2H, s, CHBr); (C8H14NOBr) δH (400 MHz,
CDCl3), 1.20-2.40 (8H, m, CHNH(CH2)4CHBr), 2.00 (3H, m,
CH3), 3.90-4.10 (2H, m, CHBr, CHNH), 5.99 (1H, m, NH);
(C8H14NOBr) δC (100 MHz, CDCl3) 23.4 (s, CH3), 24.3 (t,
CH2), 26.4 (t, C′H2), 33.2 (t, C′′H2), 37.1 (t, C′′′H2), 55.0 (d,
CH), 55.4 (d, CH), 169.7 (s, CdO).
3. Results and Discussion
Most microelectrode voltammetric experiments in [C4mim]-
[N(Tf)2] were carried out using a glass cell designed for
investigating microliter samples of ionic liquids under vacuum
conditions, a schematic of which can be found in previous
reports.22,31 A trimmed disposable micropipet tip was fitted to
the end of the microdisk electrode to provide a cavity into which
a small sample of ionic liquid (∼20 µL) was delivered. A
conventional two electrode setup was utilized with a Pt
microdisk working electrode and a 0.5 mm diameter silver (Ag)
wire (99.99%, Advent Research Materials Ltd, Oxford, U.K.)
acting as the quasi-reference electrode. The system was purged
in vacuo (Edwards High Vacuum Pump, Model ES 50) for 40
min prior to any measurements and for the duration of the
experiment thereafter.
For microelectrode experiments requiring a larger volume of
ionic liquid and those in which [C4mim][N(Tf)2] was replaced
by MeCN, a traditional five-arm glass cell was employed, in
which a Pt wire was added as a counter electrode to complete
a conventional three-electrode arrangement. These systems were
purged with nitrogen (BOC Gases, Guildford, U.K.) for 40 min
prior to any measurements and for the duration of all experi-
ments.
2.3. Instrumentation. A commercial potentiostat, PGSTAT
20 (Eco Chemie Utrecht, Netherlands), was used for the
electrochemical experiments in conjunction with a Pentium-
based PC.
Proton nuclear magnetic resonance (δH) spectra were recorded
on a Bruker AC 200 (200 MHz), Bruker AV 400 (400 MHz),
or a Bruker DPX 400 (δH) spectrometer. Spectra (400 MHz)
were assigned using COSY. Carbon nuclear magnetic resonance
(δC) spectra were recorded on a Bruker AV 400 (100.6 MHz)
spectrometer. Spectra were assigned using HMQC; multiplicities
were assigned using DEPT sequence. All chemical shifts are
quoted on the δ scale in ppm using residual solvent as internal
standard.
3.1. Oxidation of Bromide in [C4mim][N(Tf)2]. The vol-
tammetry of the oxidation of bromide was first investigated in
the RTIL 1-butyl-3-methylimidazolium bis[(trifluoromethyl)-
sulfonyl]imide ([C4mim][N(Tf)2]). Figure 1 shows the steady-
state voltammograms (10 mV s-1 scan rate) recorded for the
direct oxidation of increasing concentrations of [C2mim]Br in
[C4mim][N(Tf)2] at a platinum microdisk electrode (10 µm
diameter). Two well-defined anodic waves occur at E1/2 ) 1.1
( 0.1 V (vs Ag) and 1.5 ( 0.1 V, respectively. Bromide, Br-,
is initially oxidized to bromine, Br2 (first wave), which reacts
-
with an equivalent of Br- to form the tribromide species, Br3
:
2Br- - 2e- f Br2
(1)
(2)
Br2 + Br- h Br3
-
At higher potentials, the tribromide is oxidized further:
Br3- h Br- + Br2
(3)
(4)
(5)
Br- - e- f 1/2Br2
Overall:
Br3- - e- f 3/2Br2
The second oxidation might occur as written in eqs 3 and 4 or
via the direct oxidation of tribromide, as in eq 5.1-4 The detailed
mechanism is considered elsewhere.32
According to this mechanism, the overall number of electrons
transferred per bromide for the first limiting current (ilim,1) is
2/3; both reactions 1 and 2 are occurring. The second limiting
current (ilim,2), however, is solely due to reaction 1, and therefore
the number of electrons transferred per mole of bromide
increases to 1. Thus, the ratio of ilim,1/ilim,2 should be 1.5, which
is indeed observed under steady-state conditions (scan rate )
0.01 V s-1) at the Pt microdisk electrode over the bromide
concentration range under study (2-30 mM). A plot of limiting
current against bromide concentration (see inset, Figure 1) is
linear and a value of 1.4 ( 0.2 × 10-11 m2 s-1 was calculated
for the diffusion coefficient of bromide in the ionic liquid by
2.4. Bulk Electrolysis. Bulk electrolysis was performed at a
7 mm Pt rotating disk electrode to ensure thorough mixing of
reagents. A coiled Ag wire quasi-reference electrode and a coiled
Pt wire counter electrode completed the cell arrangement.
Lithium bromide (2 × 10-3 moles) and excess cyclohexene were

16324 J. Phys. Chem. B, Vol. 108, No. 41, 2004
Allen et al.
Figure 1. Steady-state linear sweep voltammograms (scan rate 10 mV s-1) for the oxidation of [C2mim]Br in [C4mim][N(Tf)2] at a 10 µm Pt
microdisk electrode at increasing concentrations of bromide (2-30 mM). The inset shows a plot of limiting current vs bromide concentration, ilim,1
) (2), ilim,2 ) (9).
Figure 2. Steady-state cyclic voltammograms (scan rate 10 mV s-1) for the reactivity of [C2mim]Br in [C4mim][N(Tf)2] at a 10 µm Pt microdisk
electrode at increasing concentrations of cyclohexene (3-50 mM). Also shown is a voltammogram for cyclohexene alone in [C4mim][N(Tf)2].
rearrangement of the following equation:
ensure that the organic substrate was not electroactive in the
potential window of interest. A solution of cyclohexene (∼100
mM) in [C4mim][N(Tf)2] was prepared and the potential was
swept in the anodic direction until the onset of solvent
breakdown. The resulting scan, as can be seen in Figure 2,
confirms that the voltammogram for cyclohexene alone is
essentially unchanged from the RTIL itself. To investigate the
possible reactivity, micromolar additions of cyclohexene were
then added to 20 mM [C2mim]Br/[C4mim][N(Tf)2] and their
effect studied by linear sweep voltammetry (LSV) at a platinum
microdisk electrode. The first two waves shown in Figure 2
are due to the oxidation of bromide (as explained in the previous
section), but the new, third wave, emerging at E1/2 ) 1.9 ( 0.1
V (vs Ag) is believed to be due to the direct oxidation of trans-
1,2-dibromocyclohexane (DBCH), formed upon reaction of
ilim ) 4nFrDc
(6)
where ilim is the limiting current, n is the number of electrons
transferred, F is the Faraday constant (96 485 C mol-1), r is
the radius of the microdisk electrode, D is the diffusion
coefficient of the electroactive species, and c is its bulk
concentration. This value is consistent with a previously reported
diffusion coefficient of chloride in [C4mim][BF4], where D was
found to be 1.1 × 10-11 m2 s-1 33
.
3.2. Reactivity of Electrogenerated Bromine with Cyclo-
hexene in [C4mim][N(Tf)2]. The reactivity of the electrogen-
erated bromine with cyclohexene was next investigated in
[C4mim][N(Tf)2]. The voltammetry of cyclohexene alone was
first studied on a Pt microdisk electrode in the ionic liquid to

Reactivity of Electrogenerated Br with Cyclohexene
J. Phys. Chem. B, Vol. 108, No. 41, 2004 16325
Figure 3. Steady-state linear sweep voltammograms (scan rate 10 mV s-1) for the oxidation of trans-1,2-dibromocyclohexane in [C4mim][N(Tf)2]
at a 10 µm Pt microdisk electrode at increasing concentrations (40-220 mM) in the presence of 20 mM [C2mim]Br. Also shown is a voltammogram
for the oxidation of DBCH (150 mM) alone in [C4mim][N(Tf)2].
SCHEME 1
electrogenerated bromine with cyclohexene. As is outlined in
Scheme 1, an electrophillic addition reaction occurs between
bromine and cyclohexene, whereby the bromonium intermediate
is attacked by bromide to yield the trans product. Accordingly,
the size of this third wave increases with additions of cyclo-
hexene (3-50 mM) as more DBCH is generated.
Figure 4. Steady-state cyclic voltammograms for the oxidation of [C2-
mim]Br in 0.1 M TBAP/MeCN at a 10 µm Pt microdisk electrode at
increasing concentrations of bromide (4-26 mM). The inset shows a
plot of limiting current vs bromide concentration, ilim,1 ) (2), ilim,2
(9).
)
To investigate this proposed product, the oxidation of trans-
1,2-dibromocyclohexane in [C4mim][N(Tf)2] was then studied
by LSV at a Pt microelectrode, and an anodic wave was
observed at E1/2 ) 1.9 ( 0.1 V V (vs Ag). DBCH was then
added to the [C2mim]Br/[C4mim][N(Tf)2] system so as to
emulate like reaction conditions, and as shown in Figure 3,
analogous voltammetry is observed, supporting our hypothesis.
Further evidence was then gained from performing bulk
electrolysis at a Pt rotating disk electrode on the Br-/[C4mim]-
[N(Tf)2] system, with the potential held on the plateau of the
second wave so as to generate the speculated product, DBCH,
before occurrence of its own oxidation. NMR spectroscopy gives
evidence that the isolated product is the trans-1,2-dibromo-
cyclohexane species, with a characteristic peak for the protons
on the substituted carbons appearing at 4.45 ppm. For a complete
1H NMR assignment, see section 2.4.
voltammetric time scale at the Pt microdisk electrode. In the
case of phenol, reactivity is expected to proceed via an aromatic
substitution reaction and thus the lack of a proton sink in this
medium may explain why none is observed.
3.3. Oxidation of Bromide and Reactivity of Electrogen-
erated Bromine with Cyclohexene in MeCN. For comparative
purposes, the voltammetric investigation of [C2mim]Br was
repeated in MeCN. Figure 4 shows steady-state voltammograms
measured at a platinum microdisk electrode. As can be seen,
the response in MeCN is very similar to that observed in the
ionic liquid and the oxidation is believed to proceed via the
same mechanism. The calculated diffusion coefficient, D ) 1.7
( 0.2 × 10-9 m2 s-1, is in good agreement with literature values
and appropriately larger than the value determined for the ionic
liquid given the significantly different viscosities (ηMeCN ) 0.345
cP, η[C mim][N(Tf) ] ) 44 cP at T ) 25 °C).1,15,16,34,35 The reactivity
The bromination investigation was also extended to other
organic substrates. Solutions of phenol (100 mM) and styrene
(100 mM) in [C4mim][N(Tf)2] were studied by LSV; however,
there was no evidence of the reactivity of electrogenerated
bromine in the ionic liquid with these organic substrates on the
4
2
of bromine with cyclohexene was also studied in MeCN by
linear sweep and cyclic voltammetry. A third wave is not
observed in the voltammograms (see Figure 5), indicating that

16326 J. Phys. Chem. B, Vol. 108, No. 41, 2004
Allen et al.
SCHEME 3
independent studies have shown evidence of solvent incorpora-
tion when bromine and cyclohexene are homogeneously mixed
in specific molar ratios.5,11 The NMR evidence of the acetamide
product, the absence of a third wave (due to DBCH oxidation)
and the catalytic increase seen in the second oxidative wave
strongly suggests that DBCH is not produced in this system.
We have further supported this proposition by using a computer
simulation to model the observed voltammetric response,
assuming the reaction mechanism given in Scheme 2, and it is
to those simulations which we will next turn our attention.
3.4. Modeling the Reaction of Electrogenerated Bromine
with Cyclohexene in MeCN. The reaction mechanism of the
bromination of cyclohexene in MeCN was modeled using a one-
dimensional digital simulation program (DigiSim 3.03, BAS
Technicol). The initial oxidation of bromide was simulated via
a fictitious Br• intermediate due to a inherent limitation of
Digisim, which only accepts a mechanism entered in terms of
single or multielectron-transfer steps (A h B + ne-, n > 1)
and first- or second-order homogeneous reactions.32,36 This
mechanism for bromide oxidation, involving the Br• species,
was then expanded to include the subsequent reactivity of the
electrogenerated bromine with cyclohexene (see Scheme 3).
The forward scans of the steady-state voltammograms shown
in Figure 5 were simulated in Digisim, using the approximation
of a hemispherical diffusion regime for a microelectrode, where
Figure 5. Steady-state cyclic voltammograms (scan rate 10 mV s-1
for the reactivity of [C2mim]Br in MeCN at a 10 µm Pt microdisk
electrode to increasing concentrations of cyclohexene (2-42 mM).
)
SCHEME 2
DBCH is not generated in this system; however, a catalytic
increase is seen in the second oxidative wave. Again, bulk
electrolysis was performed to determine the identity of the
product, and on the basis of the obtained NMR spectra (see
section 2.4), the product is believed to be a solvent-incorporated
acetamide, as indicated in Scheme 2. The initial reactivity step
is analogous to the RTIL; however, the bromonium intermediate
is then attacked by MeCN to yield trans-1-(N-acetylamino)-2-
bromocyclohexane. Although bromide is a better nucleophile
than MeCN, the vast excess of solvent allows it to effectively
compete with the former, preventing formation of the dibromo-
substituted product. Moreover, given the expected greater
nucleophilicity of MeCN as compared to N(Tf)2-, the solvent-
trapped adduct would not have been expected in the RTIL
medium.
This proposed mechanism would explain the increase ob-
served in the second wave, which is believed to be due to
oxidation of bromide that is regenerated in the first step of
Scheme 2, eq 9. This increase will eventually reach a limit as
the number of electrons transferred per bromide switches from
one, in the absence of cyclohexene, to two, as is evident in the
overall reaction of eqs 1 and 9:
hemisphere
disk 37,38
re
) 2/π re
.
A diffusion coefficient for cyclo-
hexene (D ) 2.4 × 10-9 m2 s-1) was estimated using the
Wilke-Chang expression39
-8
x
7.4 × 10 T xM
D )
(17)
ηV0.6
where T is the absolute temperature, x is the solvent association
constant (x ) 1 for MeCN), M is the molar mass of the solvent
(41 g mol-1), η is the solvent viscosity (0.345 cP), and V is the
volume of solute at normal boiling point (estimated from atomic
contributions39). A value for the pseudo first-order forward rate
constant for the solvent-attack step (Scheme 3, eq 16) was taken
from the literature (kf,2 ) 2 × 109 M-1 s-1).12 With all other
parameters held constant, kf,1 and the equilibrium constant (Keq,1
)
for eq 15 were adjusted so as to optimize the fit between
experimental and simulated wave shapes for the reaction of
bromine with cyclohexene. A value of 4 ( 1 × 105 M-1 s-1
was found to give the best fit for kf,1. A lower limit of 1 ×
10-3 was determined for Keq,1; the model was insensitive to
changes above this value. If Keq,1 is set any lower than this limit,
however, insufficient bromide is generated and the catalytic
increase is not observed in the simulated limiting current.
A comparison of experimental and simulated cyclic voltam-
mograms for various cyclohexene additions is shown in Figure
Therefore, the limiting current of the second wave would be
expected to double in the presence of a sufficient excess of
cyclohexene.
Although a previous report has suggested that DBCH is the
product of electrochemical bromination in acetonitrile,6 two

Reactivity of Electrogenerated Br with Cyclohexene
J. Phys. Chem. B, Vol. 108, No. 41, 2004 16327
initial bromination step and further supports the proposed
mechanism. This is the first report of a bromination reaction in
a room temperature ionic liquid and commends its potential
application in larger scale organic electrosynthesis, with the
possibility of electrogeneration of bromine from bromide.
Acknowledgment. M.C.B. thanks the Analytical Division
of the Royal Society of Chemistry for a studentship and
Alphasense for CASE funding. C.V. acknowledges support from
QUILL and The School of Chemistry, QUB.
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The reactivity of electrogenerated bromine with cyclohexene
has been investigated in both the room-temperature ionic liquid,
1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]-
imide ([C4mim][N(Tf)2]) and the traditional aprotic solvent,
acetonitrile (MeCN). We have shown that, although the direct
oxidation of bromide in both [C4mim][N(Tf)2] and MeCN results
in similar voltammetry, the reaction of electrogenerated bromine
with cyclohexene occurs via separate mechanisms and yields
different products in the two solvents as a result of their different
nucleophilicities. Bulk electrolysis, followed by NMR spec-
troscopy, confirmed that bromination in the ionic liquid results
in the formation of trans-1,2-dibromocyclohexane, whereas the
solvent-incorporated trans-1-(N-acetylamino)-2-bromocyclo-
hexane is instead synthesized in acetonitrile. The reaction in
acetonitrile has been modeled by a computer simulation program
to yield a rate constant of kf,1 ) (4 ( 1) × 105 M-1 s-1 for the