Activation and reaction volumes of the reactions of o-and p-nitrophenylsulfenyl chlorides with styrene and cyclohexene in some solvents

Article abstract of DOI:10.1007/s11172-007-0078-0

The effect of hydrostatic pressure below 1000 kg cm^-2 on the rate of reactions of o-and p-nitrophenylsulfenyl chlorides with styrene and cyclohexene was studied. The activation and reaction volumes (cm³ mol^-1) for the reactions of o-nitrophenylsulfenyl chloride with styrene in acetonitrile (-23.1 and -23.6), 1,2-dichloroethane (-29.2 and -24.7), chlorobenzene (no, -20.2), and anisole (-25.1 and -21.2) and for the reaction of p-nitrophenylsulfenyl chloride with styrene in carbon tetrachloride (-39.5±1.5 and -22.0) were determined. In carbon tetrachloride the activation volumes for the reactions of cyclohexene with o-and p-nitrophenylsulfenyl chlorides (-37.7±2.0 and -40.9±1.2 cm ³ mol^-1, respectively) are almost the same and coincide with the data for the reactions with styrene. The considerable decrease in the volume of the transition state in the nonpolar solvent is considered as a consequence of the enhanced electrostriction of carbon tetrachloride in the solvate sphere of the transition state of the reaction, which excludes the nonpolar transition state of the sulfuran type.

Full text of DOI:10.1007/s11172-007-0078-0

Russian Chemical Bulletin, International Edition, Vol. 56, No. 3, pp. 494—498, March, 2007
494
Activation and reaction volumes of the reactions
of oꢀ and pꢀnitrophenylsulfenyl chlorides with styrene
and cyclohexene in some solvents
V. D. Kiselev,ꢀ E. A. Kashaeva, L. N. Potapova, and A. I. Konovalov
A. M. Butlerov Chemical Institute, Kazan State University,
18 ul. Kremlevskaya, 420008 Kazan, Russian Federation.
Fax: +7 (843 2) 92 7278. Eꢀmail: vladimir.kiselev@ksu.ru
The effect of hydrostatic pressure below 1000 kg cm–2 on the rate of reactions of oꢀ and
pꢀnitrophenylsulfenyl chlorides with styrene and cyclohexene was studied. The activation and
reaction volumes (cm3 mol–1) for the reactions of oꢀnitrophenylsulfenyl chloride with styrene
in acetonitrile (–23.1 and –23.6), 1,2ꢀdichloroethane (–29.2 and –24.7), chlorobenzene
(no, –20.2), and anisole (–25.1 and –21.2) and for the reaction of pꢀnitrophenylsulfenyl
chloride with styrene in carbon tetrachloride (–39.5 1.5 and –22.0) were determined. In
carbon tetrachloride the activation volumes for the reactions of cyclohexene with oꢀ and
pꢀnitrophenylsulfenyl chlorides (–37.7 2.0 and –40.9 1.2 cm3 mol–1, respectively) are
almost the same and coincide with the data for the reactions with styrene. The considerable
decrease in the volume of the transition state in the nonpolar solvent is considered as
a consequence of the enhanced electrostriction of carbon tetrachloride in the solvate sphere
of the transition state of the reaction, which excludes the nonpolar transition state of the
sulfuran type.
Key words: оꢀnitrophenylsulfenyl chloride, styrene, activation volumes, reaction volumes,
solvent effect, mechanism.
Complex investigation of the nonpolar Diels—Alder
tion and reaction volumes can be determined from the
equations
reaction free of electrostriction of the medium during
solvation of the transition state made it possible to find
that in the series of solvents a noticeable change in the
activation or reaction volume is observed only for strong
specific interactions of the reactants with the medium.1,2
It has been shown additionally for the Diels—Alder reacꢀ
tion that the higher volume parameters are observed for
the processes involving small, "loosen" reactants with the
low packing coefficient in solution.3,4 Their transition to
the activated complex or adduct is always accompanied
by a considerable increase in the packing coefficient. The
van der Waals activation (∆V≠W) and reaction (∆VW) volꢀ
umes are often by 2—3 times lower by modulus than the
observed volume parameters in solution (∆V≠ and ∆V )
due to a large contribution of the change in the volume of
intermolecular holes in solution. The experimental conꢀ
firmation has been obtained recently5 from comparison
of the reaction volumes in the solid phase and in solution.
It has been shown6 for lithium perchlorate used as a model
of the ion state that the change in the partial molar volꢀ
ume (PMV) due to electrostriction of the solvent reaches
tens of cubic centimeters per mole, resulting in even negaꢀ
tive PMV value in acetone (–2 cm3 mol–1). The activaꢀ
–RT(∂lnk/∂p)Т = (∂G≠/∂p)Т = ∆V ≠ = ∆V ≠W + ∆V ≠sol, (1)
–RT(∂lnK/∂p)Т = (∂G/∂p)Т = ∆V = ∆VW + ∆Vsol (2)
,
where ∆V≠sol and ∆Vsol are the parameters of the solvent.
Taking into account the aforesaid, we should expect
low ∆V≠ and ∆VW values and their differences for both
W
polar and nonpolar processes. More substantial contribuꢀ
tions to the observed ∆V≠ and ∆V values and their differꢀ
ences are formed due to a change in the solvent packing
(∆V≠sol and ∆Vsol), especially in the solvate shell of charged
states.
Considerable attention was given to studying the elꢀ
evated pressure effect on the rate of the Menschutkin
reaction between the reactants of different structure with
different degrees of steric screening of the reaction center
and in media with different polarity.7,8 In the case of the
aminoꢀsubstituted substrates, the transition state always
contains localized (to more or less extent) charges achievꢀ
ing the limiting value in the reaction product. Electroꢀ
philic addition (AdE) of arylsulfenyl chlorides to unsaturꢀ
ated compounds is characterized by the reliable estabꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 477—480, March, 2007.
1066ꢀ5285/07/5603ꢀ0494 © 2007 Springer Science+Business Media, Inc.

Activation volumes of sulfenyl chlorides
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 3, March, 2007
495
lished features: the interaction affords βꢀhalogenthio esꢀ
ters due to transꢀaddition; the reaction rate depends
strongly on the medium polarity; the addition is not acꢀ
companied by rearrangement; nucleophilic solvents do
not compete with the halide ion and form no solvoꢀ
adducts.9—17 The proposed9 mechanism of the interacꢀ
tion with intermediate formation of the episulfonium ion
(А, Scheme 1) agrees with the high sensitivity of the reacꢀ
tion rate to the solvent polarity, and the subsequent ring
opening upon the nucleophilic attack by the chloride ion
results in the experimentally observed transꢀaddition
product.
on the properties of the reactants or medium polarity?
In our opinion, the activation volume of the reaction in
nonpolar and polar media can be most informative. High
charge separation is retained for the reaction in any media,
whereas the contribution of electrostriction in nonpoꢀ
lar solvents should be much larger than that in polar
media.1,8,18,19 If the transition state is formed from the
episulfonium complex (A or B) in polar solvents and from
sulfuran (D) in nonpolar solvents, then no electrostriction
in the solvate sphere of the transition state should be
expected.
In the present work, we studied the reactions of oꢀ (1a)
and pꢀnitrophenylsulfenyl chlorides (1b) with styrene (2)
and cyclohexene (3) in some solvents at 25 °C and under
Scheme 1
pressures below 1000 kg cm–2
.
Scheme 2
The episulfonium complexes (ESC) are rather
stable,10—12,14,17 especially at low temperature with the
–
counterions such as the BF4–, 2,4,6ꢀ(NO2)3C6H2SO3
and SbCl6– type.
,
As in the reaction of arylsulfenyl chlorides with alkꢀ
enes, these salts react readily with nucleophiles to form
transꢀaddition products,10—12,14 which allows them to be
considered as intermediates. However, already at room
temperature the ESC can include stereoconversion,
nucleophiles can add to the ESC obtained from strained
cycloalkenes, and the skeletal rearrangement and comꢀ
petitive formation of solvoadducts can occur, which is
not observed in the reaction itself. Covalent sulfuran (D)
agrees better than episulfonium intermediates (A, B, C)
with such characteristics of the reaction as transꢀaddition
and the absence of skeletal rearrangements and competiꢀ
tive solvoadducts. Anyway, it is still difficult to underꢀ
stand the strong effect of the solvent polarity on the reacꢀ
tion rate. On going from hexane to acetonitrile, the reacꢀ
tion rate constant increases more than by six orders of
magnitude.15 To explain all features of the reaction, one
can invoke the change in its mechanism to include14,17
the whole set of polar and nonpolar structures (see
Scheme 1). When the stabilizing factors (favorable elecꢀ
tronic effects of substituents in the reactant and substrate,
high solvation energy) are strongly supported, the formaꢀ
tion of the episulfonium ion (A or B) is energetically
justified. In the case of weak stabilization, the transition
state coordinate should shift toward a lowꢀpolarity prodꢀ
uct. How can be checked experimentally the probability
that the transition state formed from the episulfonium salt
(A or B) or contact ion pair (C), or lowꢀpolarity sulfuran
with covalent bonds (D) is transformed indeed depending
Rather high exothermicity of the reaction 1a + 2
determined by us using the calorimetric method
(–74.9 kJ mol–1, acetonitrile, 25 °C) virtually excludes
equilibrium of the process under working conditions and
possible difficulties in determination of the rate constants.
These data agree with the absence of the competitive
reaction of redistribution between the addition product
and high excess cyclohexene.11
The experimental data on the pressure effect on the
reaction rate constants in the studied media are collected
in Table 1.
The rate of the reaction 1a + 2 in carbon tetrachloride
turned out to be very low (k2 ≤ 1•10–6 L mol–1 s–1) and
unsuitable for spectrophotometric study in the optical
bomb and, therefore, kinetic measurements were carried
out for more reactive pꢀisomer 1b (see Table 1). At the
same time, the rate of the reaction of sulfenyl chlorides
1a,b with cyclohexene in polar media turned out to be too
high, which is inconvenient for observation in a barostat.

496
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 3, March, 2007
Kiselev et al.
Table 1. Rate constants (k2/L mol–1 s–1) of some AdE2 reactions under elevated pressure (p/kg cm–2) in the series of solvents at 25 °C
Acetonitrile
k2•102 а
1,2ꢀDichloroethane
Anisole
k2•104 а
Carbon tetrachloride
k2•104 b k2•102 c
p
p
k2•103 а
p
p
p
p
k2•105 d
0
0
4.44
4.58
5.19
5.94
6.58
6.54
7.72
9.26
9.78
12.03
0
2.13
2.65
3.08
3.46
4.31
4.60
5.68
7.03
0
0
1.77
1.73
2.05
2.51
2.65
2.77
3.12
3.32
4.17
4.22
4.93
0
4.93
6.90
7.44
8.60
8.66
8.78
0
2.01
2.91
3.85
4.11
4.89
5.58
7.83
8.78
0
0
1.53
1.57
3.18
4.03
5.72
7.03
7.28
160
290
370
515
630
770
960
145
250
295
325
325
495
515
570
905
960
203
325
386
520
564
763
852
200
285
397
475
507
695
797
953
150
295
450
500
573
685
765
813
980
464
546
867
930
936
10.4
12.4
12.3
22.9
26.0
lnk2 = –3.124 +
+ 0.001030p
(r = 0.9922);
lnk2 = –6.136 +
+ 0.00124p
(r = 0.9982);
lnk2 = –8.656 +
+ 0.001040p
(r = 0.9881);
lnk2 = –7.596 +
+ 0.001670p
(r = 0.9956);
lnk2 = –3.877+
+ 0.001726p;
(r = 0.9977);
lnk2 = –11.069 +
+ 0.001599p;
(r = 0.9969);
∆V≠exp = –26.0 0.8 ∆V≠exp = –31.3 0.8 ∆V≠exp = –26.3 1.4 ∆V≠exp = –42.2 1.5 ∆V≠exp = –43.6 0.8 ∆V≠exp = –40.4 0.8
a For reaction 1a + 2.
b For reaction 1b + 2.
c For reaction 1b + 3.
d For reaction 1a + 3.
However, the reactions in carbon tetrachloride are favorꢀ
able. As follows from the data in Table 1, in this medium
the activation volumes of all reactions studied are virtuꢀ
ally the same. The observed values of the activation volꢀ
umes were calculated from Eq. (1). The volume paramꢀ
eters of the studied reactions and compressibility of some
solvents are collected in Table 2.
The experimental values of the activation volumes
(∆V≠exp) were corrected to the contribution of the reacꢀ
tion rate change under pressure due to the increase in
the reactant concentration upon compression of soluꢀ
tions (∆nβTRT ). The data obtained on the medium effect
on the activation and reaction volumes allow one to make
some conclusions. First, the reaction volumes (1a + 2,
see Table 2) in media with different polarities are rather
constant (–22.3 1.4 cm3 mol–1), which agrees with the
low polarity of the reactants and products. Second, the
strong increase in the electrostriction of the solvent in the
transition state of the reaction (see Table 2) is proporꢀ
tional to the change in the baric dielectric constant of the
solvent18 (∂ε–1/∂p, see Table 2). These results contradict
the assumption on the nonpolar (D) type of the transition
state of the reaction under study. Moreover, the sharp
decrease in the partial molar volume of the transition
states of the reactions 1b + 2, 1b + 3, and 1a + 3 in carbon
tetrachloride corresponds to strong electrostriction of this
Table 2. Rate constants (k2/L mol–1 s–1) and partial molar volumes (V) for compounds 1a, 2, and 4а; reaction volꢀ
umes (∆V ) and activation volumes (∆V≠/cm3 mol–1), compressibility coefficients (β ), and baric dielectric conꢀ
T
stants (∂ε–1/∂p) in some solvents at 25 °C*
Solvent
k2
V
–∆V
–∆V ≠
β •106
∂ε–1/∂p•106
T
(1a + 2)
1
2
4a
CH2ClCH2Cl 2.13•10–3
126.9 117.4 219.6
121.4 114.7 212.5
123.4 115.9 219.1
125.3 115.2 219.3
123.1 115.6 216.7
24.7
23.6
20.2
21.2
22.0
29.2
23.1
—
25.1
39.5 (1b + 2)
40.9 (1b + 3)
37.7 (1a + 3)
78.8
113
74.5
66.0
107
17.9
4.0
13.7
13.5
38
MeCN
PhCl
PhOMe
CCl4
4.41•10–2
3.36•10–5
1.75•10–4
≤ 1 10–6 (1а + 2)
4.93•10–4 (1b + 2)
2.01•10–2 (1b + 3)
1.53•10–5 (1а + 3)
* Compressibility coefficients (β /bar–1) and baric dielectric constant (∂(1/ε)/∂p/bar–1) are borrowed from Ref. 18.
T

Activation volumes of sulfenyl chlorides
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 3, March, 2007
497
The enthalpy of the reaction (–74.9 1.2 kJ mol–1) between
solvent, which can appear only during solvation of highꢀ
polarity states.
reactants 1a and 2 in acetonitrile at 25 °C was calculated from the
data on the thermal effect of the reaction (–54.2 0.7 kJ mol–1
)
when mixing a weighed sample of crystals 1a with a styrene
solution (0.021 mol L–1) in the calorimeter cell (153 mL) and
from the heat of dissolution (20.7 0.5 kJ mol–1) of crystalline
sulfenyl chloride 1a in acetonitrile.
Experimental
Arylsulfenyl chlorides 1a,b (Aldrich) were purified by reꢀ
crystallization from hexane; 1a, m.p. 75—76 °C (cf. Ref. 20:
m.p. 75 °C); 1b, m.p. 46—47 °C (cf. Ref. 21: m.p. 48—49 °C).
Solvents were purified by known methods.22 Under all condiꢀ
tions studied (solvent, temperature, pressure), the unchanged
absorption of compounds 1a,b in time was checked. Spectral
purity of compounds 1a,b was monitored after the reaction comꢀ
pleted from the correspondence of the residual absorption to the
expected absorption of the adduct. Styrene was distilled in vacuo
before measurements. Product 4a, m.p. 63—64 °C (from penꢀ
tane) (cf. Ref. 23: m.p. 55.5—57.5 °C). Found (%): C, 57.30;
Н, 4.03; N, 4.65. C14H12ClNO2S. Calculated (%): C, 57.24;
H, 4.12; N, 4.77. The reaction products with cyclohexene have
been described earlier.11,20 Kinetic measurements were carried
out by a change in the absorption of reactants 1a,b in the reacꢀ
tion mixture (420—445 nm, SFꢀ46). The concentrations of styꢀ
rene and cyclohexene, which do not absorb in this region, usuꢀ
ally were 0.2 mol L–1 and exceeded the concentration of sulfenyl
chlorides by more than 20 times. Correction to absorption of the
adducts was calculated from their absorption spectra. Since adꢀ
ditives noticeably affected the reaction rate in carbon tetrachloꢀ
ride, all kinetic measurements were performed at a fixed alkene
concentration. The occurrence of the reaction with styrene acꢀ
cording to Markovnikov´s rule has been proved earlier.9 The
procedure of kinetic measurements under elevated pressure has
been described.1,19 The corrected activation volume (see Table 2)
was calculated from the experimental value (∆V≠exp, see Table 1)
The authors are grateful to workers of the Analytical
Center for Collective Use of the Kazan Research Center
of the Russian Academy of Sciences for performing
analyses.
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 05ꢀ03ꢀ
32583).
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(3)
T
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(1000 + mAMA)/d = VAmA + 1000/d0.
(4)
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2•10–3 °C. In 1,2ꢀdichloroethane the reaction volume was calꢀ
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adduct and reactants (–24.7 0.4 cm3 mol–1) and using the kiꢀ
netic method (–24.3 0.4 cm3 mol–1) from the dependence of
the solution density in time (1/d(t)) on the adduct concentraꢀ
tion (cP).
1/d(t) = 1/d(t=0) + cP ∆Vr/(1000d(t=0)).
(5)

498
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Received May 12, 2006;
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in revised form January 30, 2007