Propanolysis of arenesulfonyl chlorides: Nucleophilic substitution at sulfonyl sulfur

Article abstract of DOI:10.1002/poc.3753

We have studied the mechanism of solvolysis of arenesulfonyl chlorides by propan-1-ol and propan-2-ol at 303-323 K. Kinetic profiles were appropriately fit by first-order kinetics. Reactivity increases with electron-donating substituents. Ortho-alkyl substituted derivatives of arenesulfonyl chlorides show increased reactivity, but the origin of this “positive” ortho-effect remains unclear. Likely, ortho-methyl groups restrict rotation around the C-S bond, facilitating the attack of the nucleophile. No relevant reactivity changes have been found with propan-1-ol and propan-2-ol in terms of nucleophile steric effect. The existence of isokinetic relationships for all substrates suggests a single mechanism for the series. Solvolysis reactions of all substrates in both alcohols show isokinetic temperatures (T_iso) close to the working temperature range, which is an evidence of the process being influenced by secondary reactivity factors, likely of steric nature in the TS. Solvation plays a relevant role in this reaction, modulating the reactivity. In some cases, the presence of t-Bu instead of Me in para- position leads to changes in the first solvation shell, increasing the energy of the reaction (ca. 1?kJ·mol^?1). The obtained results suggest the same kinetic mechanism of solvolysis of arenesulfonyl chlorides for propan-1-ol and propan-2-ol, as in MeOH and EtOH, where bimolecular nucleophilic substitution (S_N2) takes place with nucleophilic solvent assistance of one alcohol molecule and the participation of the solvent network involving solvent molecules of the first solvation shell.

Full text of DOI:10.1002/poc.3753

Received: 6 March 2017
DOI: 10.1002/poc.3753
Revised: 9 June 2017
Accepted: 12 July 2017
R E S E A R C H A R T I C L E
Propanolysis of arenesulfonyl chlorides: Nucleophilic
substitution at sulfonyl sulfur
Mykyta Iazykov1,2
| Moisés Canle2
| J. Arturo Santaballa2
| Ludmila Rublova1
1 Department of General Chemistry,
Faculty of Ecology and Chemical
Technology, Donetsk National Technical
University, Donetsk, Ukraine
2 Department of Chemistry, Faculty of
Sciences and CICA, Universidade da
Coruña, Chemical Reactivity and
Abstract
We have studied the mechanism of solvolysis of arenesulfonyl chlorides by
propan‐1‐ol and propan‐2‐ol at 303‐323 K. Kinetic profiles were appropri-
ately fit by first‐order kinetics. Reactivity increases with electron‐donating
substituents. Ortho‐alkyl substituted derivatives of arenesulfonyl chlorides
show increased reactivity, but the origin of this “positive” ortho‐effect
remains unclear. Likely, ortho‐methyl groups restrict rotation around the
C‐S bond, facilitating the attack of the nucleophile. No relevant reactivity
changes have been found with propan‐1‐ol and propan‐2‐ol in terms of
nucleophile steric effect. The existence of isokinetic relationships for all sub-
strates suggests a single mechanism for the series. Solvolysis reactions of all
substrates in both alcohols show isokinetic temperatures (Tiso) close to the
working temperature range, which is an evidence of the process being influ-
enced by secondary reactivity factors, likely of steric nature in the TS. Sol-
vation plays a relevant role in this reaction, modulating the reactivity. In
some cases, the presence of t‐Bu instead of Me in para‐ position leads to
changes in the first solvation shell, increasing the energy of the reaction
(ca. 1 kJ·mol−1). The obtained results suggest the same kinetic mechanism
of solvolysis of arenesulfonyl chlorides for propan‐1‐ol and propan‐2‐ol, as
in MeOH and EtOH, where bimolecular nucleophilic substitution (SN2)
takes place with nucleophilic solvent assistance of one alcohol molecule
and the participation of the solvent network involving solvent molecules
of the first solvation shell.
Photoreactivity Group, A Coruña, Spain
Correspondence
Mykyta Iazykov, Universidade da Coruña,
Chemical Reactivity and Photoreactivity
Group, Department of Chemistry, Faculty
of Sciences and CICA, E‐15071 A Coruña,
Spain.
Email: nikitich205@gmail.com;
mcanle@udc.es; arturo@udc.es
Funding information
TEMPO, Grant/Award Number: 372283‐1‐
2012‐1‐PT‐ERA MUNDUS‐EMA21
KEYWORDS
alcoholysis, arenesulfonyl chlorides, nucleophilic solvent assistance, nucleophilic substitution,
positive ortho‐effect, solvent effects
1 | INTRODUCTION
It is generally accepted[1–6] that most sulfonyl
chlorides undergo solvolysis through bimolecular
Nucleophilic substitution reactions near sulfonyl sulfur
have been thoroughly studied.[1–15] However, the
available literature is often contradictory and
occasionally related to rather limited sets of substrates.
mechanisms. However, there are known SN1‐type
reactions for several substrates. Thus, Hall and Robert-
son[7,8] assumed the hydrolysis of N,N‐dimetylsulfamoyl
chloride is a unimolecular process, based on the small
J Phys Org Chem. 2017;e3753.
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https://doi.org/10.1002/poc.3753

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IAZYKOV ET AL.
solvent kinetic isotope effect (SKIE) (kH2O/kD2O = 1.33)
and low sensitivity of the studied substrates to nucleo-
phile changes in aqueous 1,4‐dioxane solutions (86.1/
Scheme 1 can be considered as bimolecular with the
additional participation of solvent molecules through a
general‐base catalysis‐like process.
13.9%V/V) ([Piperidine] = 0.0231 M, k = 4.6 s−1
;
The reason for increased reactivity on sterically
hindered derivatives of sulfonic acids relative to the
unhindered analogues in solvolysis reactions (“positive”
ortho‐effect) remains unclear.[26–28] Attempts to interpret
this behavior in terms of a change in reaction mechanism
to unimolecular[26] are derived from the existence of
hyperconjugation,[12] and from steric and structural
features in the TS.[27] However, the magnitude of these
effects does not fully support the shift from bimolecular
to unimolecular.
[NaOH] = 0.0138 M, k = 4.9 s−1; [NaClO4] = 0.0068 M,
k = 5.09 s−1). Maskill, based on data on solvolysis in
2,2,2‐trifluoroethanol, concluded the solvolysis of 4‐N,N‐
(dimethylamino)benzenesulfonyl chloride takes place
through an SN2 mechanism, where bond breaking signif-
icantly prevails over bond formation at the TS.[9] This was
later confirmed by results on the solvolysis of this com-
pound in 80 % aqueous acetic acid and hydrolysis at dif-
ferent pH values.[6]
Haughton et al proposed the solvolysis of arenesulfonyl
halides implies the formation of a pentacoordinate inter-
mediate.[10] An addition‐elimination mechanism (SAN)
has also been proposed for the reaction of thiophene‐2‐
sulfo halides with anionic and neutral nucleophiles,[11,12]
and in the alkaline hydrolysis of arenesulfonyl fluorides[13]
and 2,4,6‐trimethylbenzenesulfonyl chloride,[14] but the
presence of the corresponding intermediates has not been
proved yet.
Currently, there is no definitive evidence of SN1 mech-
anism for the solvolysis of arenesulfonyl chlorides. The
detailed aspects of the bimolecular mechanism remain
under debate, mainly focused on the relevance of SN2
and SAN pathways.[15]
At the same time, some results point to an SN2
solvolysis mechanism for most compounds, based on the
absence of salt and “common ion” effects,[16] increase of
reactivity in the presence of strong nucleophiles,
sensitivity to the ionizing power of the solvent, and the
lack of detection of sulfonium intermediate ions.[17–19]
Different results pointing to a so‐called SN3‐mecha-
nism in the solvolysis of sulfonyl compounds have been
also obtained.[20–25] Such mechanism (Scheme 1)
accounts for the participation of a second solvent
molecule in the TS, which would facilitate formation of
the S···O bond, as in general base catalysis in water:
The SN3‐mechanism is supported by a sufficiently
high kinetic isotope effect, SKIE >2, and an important
influence of solvent nucleophilicity on reactivity.
According to the literature,[20] this mechanism is inherent
for substrates such as 4‐nitrobenzenesulfonyl chloride
and 4‐methoxybenzenesulfonyl chloride. The process in
Methanolysis and ethanolysis are the most widely
studied processes of nucleophilic substitution in
arenesulfonyl halides with the participation of alcohols,
most of them being carried out in alcohol‐water mixtures,
which implies the presence of 2 competing solvolysis
pathways: alcoholysis and hydrolysis.[2,5,15,20,22,28] For this
reason, alcoholysis of arenesulfonyl halides in propan‐1‐ol
and propan‐2‐ol has received scarce consideration, thus
being interesting to study the features of arenesulfonyl
chlorides solvolysis by bulkier nucleophiles like propan‐
1‐ol (n‐PrOH) and propan‐2‐ol (i‐PrOH).
The main objective of this work is to understand the
influence of steric hindrance of both, substrate and nucle-
ophile, on the mechanism of arenesulfonyl chlorides sol-
volysis by propan‐1‐ol and propan‐2‐ol in the
temperature range 303‐323 K (Scheme 2).
2 | RESULTS AND DISCUSSION
Absorbance vs time profiles of the neutral propanolysis
of aromatic sulfonyl chlorides by propan‐1‐ol and
propan‐2‐ol were adequately fitted by a first‐order kinetic
model, and the corresponding rate constants are com-
piled in Tables 1 and 2. Solvolysis is sensitive to the
nature and position of the substituents and shows a com-
plex and ambiguous influence of the electronic nature of
ring substituents (X). 4‐NO2 and 3‐NO2 derivatives show
enhanced reactivity whereas the rather low reactivity of
SCHEME 2 Solvolysis of arenesulfonyl chlorides (X‐ArSO2Cl) by
propan‐1‐ol and propan‐2‐ol (*these substrates were not studied in
iso‐propanolysis) R = n‐Pr; i‐Pr X = H; 4‐Me; 4‐t‐Bu; 4‐Cl*; 4‐Br;
3‐NO2*; 4‐NO2; 2,4,6‐Me3; 2,4,6‐Et3; 2,4,6‐i‐Pr3; 2‐Me; 2,4‐Me2;
2,5‐Me2; 2‐Me‐5‐t‐Bu; 2,6‐Me2‐4‐t‐Bu; 2,3,5,6‐Me4; 2‐Me‐5‐NO2;
2,4‐Me2‐5‐NO2; 2,4,6‐Me3‐3‐NO2; 2,4,6‐(OMe)3
SCHEME
1
“Trimolecular”
nucleophilic
substitution
mechanism (SN3) in the hydrolysis of arenesulfonyl chlorides

IAZYKOV ET AL.
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TABLE 1 Observed rate constants for neutral n‐propanolysis of X‐ArSO2Cl
kobs·104/s−1
X
303 K
313 K
323 K
4‐t‐Bu
0.138 0.001
0.339 0.003
0.573 0.007
1.16 0.01
1.09 0.01
0.975 0.005
0.946 0.005
1.24 0.02
1.26 0.06
1.43 0.01
1.24 0.01
1.36 0.01
1.27 0.01
3.66 0.02
1.08 0.01
1.49 0.02
5.06 0.01
6.33 0.03
6.13 0.02
4.07 0.03
1.91 0.01
1.36 0.01
4‐Me
0.224 0.001
0.203 0.001
0.185 0.004
0.170 0.005
0.267 0.006
0.255 0.007
0.281 0.001
0.255 0.001
0.315 0.004
0.255 0.001
0.869 0.005
0.202 0.003
0.316 0.006
1.42 0.01
0.506 0.002
0.488 0.003
0.450 0.007
0.422 0.006
0.57 0.01
H
4‐Br
4‐Cl
3‐NO2
4‐NO2
0.62 0.04
2,4‐Me2
0.705 0.003
0.574 0.004
0.695 0.005
0.581 0.001
2.00 0.02
2‐Ме‐5‐t‐Bu
2,5‐Me2
2‐Ме
2,4,6‐Me3‐3‐NO2
2,4‐Ме2‐5‐NO2
2‐Me‐5‐NO2
2,4,6‐(OMe)3
2,6‐Ме2‐4‐t‐Bu
2,4,6‐Me3
2,3,5,6‐Ме4
2,4,6‐Et3
2,4,6‐i‐Pr3
0.463 0.005
0.695 0.004
2.95 0.01
1.50 0.01
3.43 0.01
1.39 0.01
3.03 0.01
1.00 0.01
1.96 0.01
0.408 0.002
0.312 0.002
0.923 0.004
0.684 0.001
4‐t‐Bu derivative relative to H; 4‐Me; 4‐Cl; 4‐Br sulfonyl
chlorides could be explained by solvation changes at
the TS.
As for n‐PrOH, the solvolysis in iso‐propanol of the
following X‐ArSO2Cl compounds: 2,4,6‐Me3;
2,4,6‐Et3; 2,6‐Me2‐4‐t‐Bu; 2,3,5,6‐Me4; 2‐Me‐5‐NO2; 2,4,6‐
Me3‐3‐NO2 and 2,4,6‐(OMe)3 also displays anomalous
acceleration (Table 2 and Figure 2).
X
=
As shown in Figure 1, the following alkyl‐ortho‐
substituted compounds: X = 2,4,6‐Me3; 2,4,6‐Et3; 2,6‐
Me2‐4‐t‐Bu; 2,3,5,6‐Me4; 2‐Me‐5‐NO2; 2,4‐Me2‐5‐NO2;
2,4,6‐Me3‐3‐NO2; 2,4,6‐(OMe)3; 2‐Me; 2,4‐Me2; 2,5‐Me2
display solvolysis acceleration in n‐PrOH relative to
unsubstituted sulfonyl chlorides (Table 1 and Figure 1).
The most reactive compounds include all those
substituted in both ortho‐ positions by ‐Me groups. The
reactivity of 2,4,6‐Et3‐ and 2,4,6‐i‐Pr3‐derivatives is lower
than for di‐ortho‐Me‐derivatives and a bit higher than
for the rest of compounds, which can be explained as a
balance between the accelerating effect of ortho‐alkyl
groups and the nucleophile bulkiness.
It is noticeable that there is no clear quantitative
correlation between reactivity and the electronic effect of
ring substituents analyzed in terms of Hammett sigma
constants (Figure 1). In general, at least qualitatively,
reactivity seems to increase with the number of alkyl
substituents, although the steric effect of ortho‐substitu-
ents should also be kept in mind.
Again, the most reactive compounds correspond to
those substituted in both ortho‐ positions by Me groups
and, as above, 2,4,6‐Et3 and 2,4,6‐i‐Pr3‐derivatives show
a reactivity lower than the rest of di‐ortho‐methylated
compounds. In both solvents, the alcoholysis rate of
X‐ArSO2Cl derivatives follows the order di‐ortho‐alkyl
substituted > mono‐ortho‐alkyl substituted > non‐ortho‐
alkyl substituted.
Although, as stated before, no general Hammett0s cor-
relations are observed including all the studied substrates;
it is noticeable the different reactivity order of some
4‐substituted X‐ArSO2Cl in n‐PrOH and in i‐PrOH, see
inset of Figures 1 and 2. To highlight such difference,
Hammett0s ρ0s have been estimated for the solvolysis of
4‐substituted derivatives (Table 3). Hydrolysis of the con-
sidered compounds showed a negative Hammett slope
(ρ = −0.52 0.08, r = 0.93), similar to that obtained con-
sidering the 13 available values in the literature

4 of 10
IAZYKOV ET AL.
TABLE 2 Observed rate constants for neutral iso‐propanolysis of X‐ArSO2Cl
kobs·105/s−1
X
303 K
313 K
323 K
4‐t‐Bu
0.239 0.006
0.49 0.01
0.965 0.006
4‐Me
Hb
0.33 0.01
0.33 0.01
0.457 0.001
1.07 0.01
0.46 0.01
0.305 0.003
0.368 0.007
0.401 0.009
0.43 0.01
0.53 0.01
2.16 0.01
2.58 0.07
2.06 0.02
1.55 0.02
1.91 0.03
0.512 0.005
0.32 0.01
0.657 0.008
0.80 0.01
0.989 0.001
2.45 0.01
1.05 0.01
0.788 0.008
0.83 0.01
0.92 0.02
0.933 0.005
1.24 0.01
4.23 0.01
4.67 0.01
4.38 0.01
3.09 0.01
3.79 0.03
0.992 0.001
0.700 0.005
1.52 0.03
1.84 0.02
2.42 0.01
5.32 0.01
2.47 0.01
1.66 0.01
1.87 0.01
2.03 0.01
1.93 0.02
2.52 0.02
8.67 0.01
8.90 0.03
8.37 0.03
5.96 0.02
7.17 0.02
2.00 0.02
1.25 0.01
4‐Brb
a
4‐NO2
b
2,4‐Me2
2‐Ме‐5‐t‐Bu
2,5‐Me2
2‐Ме
2,4‐Ме2‐5‐NO2
2‐Me‐5‐NO2
b
2,4,6‐(OMe)3
2,6‐Ме2‐4‐t‐Bub
b
2,4,6‐Me3
b
2,3,5,6‐Ме4
b
2,4,6‐Me3‐3‐NO2
2,4,6‐Et3
b
2,4,6‐i‐Pr3
aData taken from[29]
bRate constants (323 K) from ref.[30]
.
FIGURE 1 Log kobs vs Hammett sigma constants[31] for the n‐
propanolysis of X‐ArSO2Cl at 313 K. ; non‐ortho and mono‐ortho‐
alkylated compounds; di‐ortho‐alkylated compounds. Inset:
Hammett plot for 4‐X‐ArSO2Cl
FIGURE 2 Log kobs vs Hammett sigma constants[31] for the iso‐
propanolysis of X‐ArSO2Cl at 313 K. non‐ortho and mono‐ortho‐
alkylated compounds; di‐ortho‐alkylated compounds. Inset:
Hammett plot for 4‐X‐ArSO2Cl
(ρ = −0.42 0.04, r = 0.91). Poor correlations with positive
Hammett slopes (ρ ≥ 0) were found for MeOH, EtOH, and
propan‐1‐ol, ie, alcoholysis increases with electron‐
withdrawing groups. Positive Hammett slope and good
correlation was obtained for iso‐propanolysis (ρ c.a. 0.65,
r > 0.92).

IAZYKOV ET AL.
5 of 10
TABLE 3 Hammett constants (ρ) for neutral solvolysis of X‐
and S‐Cl bond breaking are related to sulfonyl chloride
structure and solvent, ie, not only electronic factors
should be considered when comparing the behavior in
different alcohols.
ArSO2Cla
Solvolysis
Hydrolysisb
T/K
ρ
r
303
−0.52 0.08
0.93
The obtained activation parameters are collected in
Table 4. The non‐ortho‐substituted series is isoenthalpic
as ΔH╪ depends weakly on the X substituent, and only
the 4‐t‐Bu derivative shows a slight decrease. Both in
propan‐1‐ol and in propan‐2‐ol, ΔH╪ decreases with the
introduction of di‐ortho‐alkyl groups on the aromatic ring,
whereas ΔS╪ increases, a clear example of a compensation
effect[32] (see Figures S1 and S2 in the Supporting
Information).
Although caution should be taken in the analysis of
ΔH╪ vs ΔS╪,[32,33] from there it follows that for each com-
pound ΔH╪ is similar in propan‐1‐ol and propan‐2‐ol,
whereas ΔS╪ is more negative in the later, which suggests
a more ordered TS in i‐PrOH. The absence of significant
fluctuations between free activation energies suggests
the same basic mechanism of solvolysis for all the studied
substrates in both alcohols.
Methanolysisc
Ethanolysisc
323
323
0.29 0.14
0.39 0.15
0.40
0.54
n‐propanolysis
303
313
323
0.15 0.11
0.16 0.09
0.18 0.14
0.16
0.32
0.11
iso‐propanolysisd
303
313
323
0.61 0.07
0.67 0.07
0.66 0.10
0.95
0.96
0.92
aX: H; 4‐Me; 4‐t‐Bu; 4‐Cl; 4‐Br; 4‐NO2.
bThe rate constants used in this correlation are taken from ref.[10] 4‐tBu and
4‐NO2 not included.
cSome of the rate constants used in this correlation are taken from ref.[30] The
full set of data is available as a Table S8 in the Supporting Information.
d4‐Cl not included.
This does not necessarily imply different reaction
mechanism, likely changes in alcohol‐sulfur bond making
TABLE 4 Activation parameters for the neutral alcoholysis of X‐ArSO2Cl in n‐PrOH and i‐PrOH
ΔH╪a/ kJ·mol−1
n‐PrOH
‐ΔS╪a/ J·mol−1·K−1
ΔG╪ a,b/ kJ·mol−1
n‐PrOH i‐PrOH
X
i‐PrOH
n‐PrOH
i‐PrOH
191
172 15
147
4‐t‐Bu
56
65
66
68
66
61
63
64
62
58
64
66
61
50
57
59
55
57
61
58
4
2
1
1
1
1
3
4
1
2
1
2
1
3
4
1
2
4
1
1
55
60
68
66
‐‐
1
5
1
4
173 13
3
111
109
109
110
110
109
109
109
109
109
109
109
108
104
104
105
106
106
108
109
9
3
1
2
3
3
6
8
1
4
1
3
1
7
8
1
5
8
2
2
115
114
114
113
‐‐
2
9
2
8
4‐Me
H
141
137
133
140
154
146
5
2
3
5
4
9
2
4‐Br
4‐Cl
150 13
‐‐
‐‐
3‐NO2
4‐NO2
‐‐
‐‐
c
63
67
68
64
64
58
62
55
49
55
53
52
54
54
1
2
3
1
1
3
1
2
2
2
1
1
2
4
152
148
1
6
111
113
114
114
114
114
113
110
109
110
110
110
113
114
1
4
6
2
2
5
3
4
4
3
1
1
4
8
2,4‐Me2
141 12
2‐Ме‐5‐t‐Bu
2,5‐Me2
148
162
145
138
151
1
6
1
5
2
147 10
158
159
176
164
175
194
173
183
184
190
3
4
8
4
7
7
5
1
1
6
2‐Ме
2,4‐Ме2‐5‐NO2
2‐Me‐5‐NO2
2,4,6‐(OMe)3
2,6‐Ме2‐4‐t‐Bu
2,4,6‐Me3
175 11
151 12
147
161
2
7
2,3,5,6‐Ме4
2,4,6‐Me3‐3‐NO2
2,4,6‐Et3
157 13
149
161
3
4
2,4,6‐i‐Pr3
193 12
aEstimated considering the second‐order rate constant k2, ie, kobs = k2·[solvent].
bValue calculated at 40°C.
cData taken from ref.[30]

6 of 10
IAZYKOV ET AL.
The existence of a log kT1 vs log kT2 isokinetic
substrates and the strong heterogeneity of the studied
series. To facilitate the discussion, the obtained data
were divided into 3 subgroups: non‐ortho‐methylated (1),
mono‐ (2), and di‐ortho‐alkylated (3). There is no
common point of intersection of all kinetic curves both
in propan‐1‐ol and in propan‐2‐ol (see Figures S3 and S4
in the Supporting Information); therefore, we should
discuss, more properly, isokinetic ranges for subgroups
of substrates. Tiso was estimated by linear extrapolation
of the experimental data using linear least squares
(Table 5).[34]
dependence for all substrates in n‐PrOH (r = 0.992‐0.995,
Figure 3) and i‐PrOH (r = 0.975‐0.990, Figure 4) also
points to a common alcoholysis reaction mechanism.
Evaluation of the isokinetic temperature (Tiso) is
complicated both by the large variety of considered
The higher steric hindrance near the sulfonyl group,
the greater the entropic contribution, which brings the
TS to the entropy control zone already in the operating
temperature region.[35] This rare phenomenon is quite
peculiar to compounds of similar structure.[36]
Tiso of non‐ortho‐methylated and mono‐ortho‐methyl-
ated compounds slightly declines as nucleophile bulki-
ness increases. Tiso for di‐ortho‐methylated substrates is
the same in n‐PrOH and i‐PrOH, which points to a more
rigid TS structure, likely due to the presence of the 2
ortho‐ methyl groups. Nevertheless, the lower boundary
of entropy zone control in all cases has a tendency to
decrease in the case of iso‐propanolysis.
Such behavior cannot be explained solely by electronic
effects in the substrates. Because the working temperature
range is close to the isokinetic temperatures, caution
should be taken when interpreting substituents effects
for both alcohols.[33]
FIGURE 3 log kT1 vs log kT2 dependence for X‐ArSO2Cl n‐
propanolysis at 303‐323 K. □ ( )T1 = 303 K; T2 = 313 K; Δ (
T1 = 303 K; T2 = 323 K; ) T1 = 313 K; T2 = 323 K
)
(
Some researchers postulate an SN2 mechanism for
methanolysis and ethanolysis of arenesulfonyl chlo-
rides.[1,2,20,28,37] The same should apply to n‐propanolysis
and i‐propanolysis, although the degree of S‐Cl bond
breaking and S‐O bond forming could change between
alcohols.
In addition to the influence of temperature, to analyze
the alcoholysis mechanism of arenesulfonyl chlorides, we
should consider electronic and steric effects, both in the
sulfonyl chloride and in the nucleophile, which at the
same time is the solvent, as well as solvation effects.
Propanolysis of arenesulfonyl chlorides (X‐ArSO2Cl)
displays a weak dependence on the electronic properties
of X substituent: di‐ortho‐alkylated substrates react faster
FIGURE 4 log kT1‐log kT2 dependence for the X‐ArSO2Cl iso‐
propanolysis at 303‐323 K. □ ( ) T1 = 303 K; T2 = 313 K; Δ (
T1 = 303 K; T2 = 323 K; ) T1 = 313 K; T2 = 323 K
)
(
TABLE 5 Isokinetic temperatures for n‐propanolysis and iso‐propanolysis of X‐ArSO2Cl
Tisoa/K
Alcoholysis of X‐ArSO2Cl
n‐propanolysis
iso‐propanolysis
Non‐ortho‐alkylated substrates (1)
293
320
313
7
5
8
264 12
Mono‐ortho‐alkylated substrates (2)
Di‐ortho‐alkylated substrates (3)
306
308
3
7
a2,4,6‐Et3‐benzenesulfonyl chloride and 2,4,6‐i‐Pr3‐benzenesulfonyl chloride were not used in the calculation.

IAZYKOV ET AL.
7 of 10
TABLE 6 Alcoholysis rate ratio (kn‐PrOH/ki‐PrOH) of X‐ArSO2Cla
effects using Taft0s[31] or Charton0s[38] steric constants by
mono‐ and multidimensional regression analysis was
unsuccessful.
T/K
X
303
313
323
Average
Alcoholysis rates of alkyl substituted arenesulfonyl
chlorides are ca. 6‐fold to 11‐fold faster in n‐PrOH than
in i‐PrOH (Table 6) irrespective of whether H or Me
groups are bonded to carbons, even at ortho‐ positions.
The same is observed when t‐Bu is the substituent at the
para‐ position. Assuming, as suggested by isokinetic
temperatures, the same solvolysis mechanism in n‐PrOH
and i‐PrOH, those values imply similar intermolecular
interactions in both alcohols.
The ratio kn‐PrOH/ki‐PrOH increases when ethyl or iso‐
propyl groups are present at both ortho‐ positions, thus
reflecting their effects, electronic and mainly steric, on
the alcoholysis rate. On the other hand, such ratio
changes with non‐alkyl substituents, suggesting different
electronic effect, compared with alkyl groups, on the
transition state polarity.
4‐t‐Bu
5.77
6.92
5.94
6.2 0.6
4‐Me
6.79
6.15
4.05
2.38
6.11
8.36
8.56
6.36
4.70
5.96
6.57
5.81
6.75
6.45
7.97
9.75
7.70
6.10
4.55
2.53
6.71
7.28
8.37
6.32
4.96
5.60
6.97
7.34
6.92
6.34
9.30
9.77
7.63
5.92
4.03
2.37
5.79
7.47
7.27
6.26
5.60
5.91
5.84
7.11
7.32
6.83
9.55
10.88
7.4 0.5
6.1 0.1
4.2 0.3
2.4 0.1
6.2 0.5
7.7 0.6
8.1 0.7
6.3 0.1
5.1 0.5
5.8 0.2
6.5 0.6
6.8 0.8
7.0 0.3
6.5 0.3
8.9 0.9
10.1 0.6
H
4‐Br
4‐NO2
2,4‐Me2
2‐Ме‐5‐t‐Bu
2,5‐Me2
2‐Ме
2,4‐Ме2‐5‐NO2
2‐Me‐5‐NO2
2,4,6‐(OMe)3
2,6‐Ме2‐4‐t‐Bu
2,4,6‐Me3
2,3,5,6‐Ме4
2,4,6‐Et3
2,4,6‐i‐Pr3
From Tables 1 and 2, and published research,[30] it
follows that not only electronic effects play a role in the
alcoholysis of arenesulfonyl chlorides.[33] Although no
Hammett correlations have been found, there is a
tendency for the reactivity to increase with the number
of alkyl substituents (Tables and Figures 1 and 2), but at
the same time, the reaction rate of non‐ortho‐alkylated
substrates is reduced by 30% when H‐ or Me‐ is replaced
by t‐butyl in para‐ position (Table 7).
It is well known that the nature of the solvent may
affect solvolysis processes largely.[40] In the case of highly
structured solvents such as water or alcohols, additional
solvation effects arise that may play a crucial role in
formation of the TS. Further, it is also known that the
studied alcohols form linear and ring chain networks,
associated through hydrogen bonds.[41,42] Hence, part of
this intermolecular bonds is shared with the TS.
aRatio of observed first‐order constants (kobs).
than non‐ortho‐alkylated substrates. The same behavior is
observed in their methanolysis and ethanolysis,[28,31] sug-
gesting a similar mechanism for the 4 alcohols. Such reac-
tivity order cannot be only explained in terms of
electronic effects. Likely, both o‐methyl groups impede
the rotation of the SO2Cl group around the C‐S bond, thus
facilitating the attack of the alcohol. The accelerating
effect of ortho‐alkyl groups differs from the usual inhibi-
tion caused by steric hindrance. Evaluation of steric
TABLE 7 Alcoholysis rate ratios (kX‐ArSO2Cl/kY‐ArSO2Cl) of X‐ArSO2Cla
Alcohol
T/K
303
313
323
MeOHb
k
k
k
2,6‐Ме2‐4‐t‐Bu‐/k2,4,6‐Me3‐
2,6‐Ме2‐4‐t‐Bu‐/k2,4,6‐Me3‐
2,6‐Ме2‐4‐t‐Bu‐/k2,4,6‐Me3‐
1.04
0.97
1.13
EtOHc
EtODc
n‐PrOH
1.00
1.09
1.14
1.12
1.11
1.06
k
k
k
4‐t‐Bu‐/k4‐Me‐
4‐t‐Bu‐/kH‐
2,6‐Ме2‐4‐t‐Bu‐/k2,4,6‐Me3‐
0.62
0.68
1.08
0.67
0.69
1.13
0.49
0.53
1.03
i‐PrOH
k
k
k
4‐t‐Bu‐/k4‐Me‐
4‐t‐Bu‐/kH‐
2,6‐Ме2‐4‐t‐Bu‐/k2,4,6‐Me3‐
0.72
0.72
1.25
0.75
0.61
1.07
0.63
0.52
1.06
aRatio of observed first‐order constants (kobs).
bData from ref.[30]
cData from ref.[39]

8 of 10
IAZYKOV ET AL.
The TS should be similar for 4‐Me‐ArSO2Cl and 4‐t‐
is SN2 and involves nucleophilic solvent assistance. Sulfur
atom is back‐side attacked by the nucleophile (a neutral
alcohol molecule), and within the same frame time, its
hydrogen is transferred to another alcohol molecule
(hydrogen atom in bold in Scheme 2), and the chloride
is expelled out. Although there is no clear pattern of elec-
tronic effects related to the studied substrates, the general
trend is for the reactivity to increase with the number of
alkyl substituents.
ortho‐Methyl substitution speeds up the solvolysis, at
least by 5‐fold in the case of di‐ortho‐methyl arenesulfonyl
chlorides. Likely, ortho‐methyl groups restrict rotation
around the C‐S bond, making easier the attack of the
nucleophile. Reactivity decreases with bulkier alkyl
groups in ortho‐ position: rotation is limited, but steric
hindrance also plays a role. Hence, the positive ortho‐
effect can be explained in the framework of the SN2
mechanism.
Solvation plays a relevant role in this reaction, modu-
lating the reactivity, with the same pattern being
observed in both propanols. The propanolysis reaction
rate is reduced by 30% on going from 4‐Me‐ArSO2Cl to
4‐t‐Bu‐ArSO2Cl, which is a direct consequence of the
effect of para‐ substituents on the first solvation shell.
These affect the orientation of the attacking nucleophile,
which implies an increase in the energetic of the reaction
(ca. 1 kJ·mol−1). On the other hand, the propanolysis
reaction rate is slightly higher for 2,6‐Ме2‐4‐t‐Bu‐ArSO2
Cl than for 2,4,6‐Ме3‐ArSO2Cl, which means that the
presence of di‐ortho‐Me substituents is not relevant in
terms of solvation, the observed change due to the alkyl
substituent in para‐ position. It follows that a detailed
modeling of the alcoholysis of arenesulfonyl chlorides
requires not only the consideration of the sulfonyl chlo-
ride, the attacking alcohol molecule, and the solvent
molecule acting as a nucleophilic assistant, solvent alco-
hol molecules forming H‐bonded networks with the
attacking nucleophile, and, in case, ring substituents
should be taken into account.
Bu‐ArSO2Cl, so similar reaction rates can be expected as
the electronic effect of both groups in para‐ position is
similar. The change in alcoholysis rate upon t‐Bu substitu-
tion, relative to unsubstituted or 4‐Me‐ArSO2Cl, should
exclusively come from changes in solvation.
From Table 7, it follows that the destabilizing effect
(ca. 1 kJ·mol−1) of a t‐Bu group in the para‐ position on
the alcoholysis rate, relative to 4‐H‐ or 4‐Me‐ArSO2Cl, is
similar in both n‐PrOH and i‐PrOH. The t‐butyl group
imposes changes in the first solvation shell, which affect
the position of the alcohol molecule attacking the sulfur
atom, and leads to a change in solvation energy,
increasing the Gibbs activation energy. Similar slowing
effect of the t‐Bu group in para‐ position has been
reported while studying the acid‐catalyzed esterification
of substituted benzoic acids by MeOH, where the
authors claimed that bulky alkyl groups in para‐posi-
tion could impose different orientation of solvent
dipoles in this region, thus changing the solvation
energy.[43]
This reduction in alcoholysis rate is not observed
when t‐Bu replaces Me in the para‐ position, when
di‐ortho‐Me substrates are considered. Even more,
2,6‐Ме2‐4‐t‐Bu‐ArSO2Cl reacts slightly faster than
2,4,6‐Ме3‐ArSO2Cl, irrespectively of the alcohol
(Table 7). likely due to the slightly higher inductive
effect of the t‐Bu group. This is a direct consequence
of the structure of the first solvation shell. Apparently,
the presence of di‐ortho‐methyl groups constrains the
orientation of the alcohol molecules solvating the TS
and canceling out differences in solvation between 4‐
t‐Bu and 4‐Me groups.
3 | CONCLUSIONS
Alcoholysis of arenesulfonyl chlorides in propan‐1‐ol and
propan‐2‐ol is similar to that observed in methanol and
ethanol, and even in water. The uniqueness of the
mechanism in each propanol is supported by the
isokinetic relations log kT1‐log kT2 (Figures 1 and 2) and
ΔH╪ vs ΔS╪ (Figures S1 and S2 of Supporting
Information).
Analysis of kinetic data, obtained in propan‐1‐ol and
propan‐2‐ol at different temperatures, does not imply a
change in the reaction mechanism due to their structure
and/or increased size. The so‐called “positive ortho‐effect”
is similar in both propanols, as in methanol and ethanol,
and the structure and/or size of the nucleophile (propan‐
1‐ol or propan‐2‐ol) has no relevant effect other than
because of their different polarity. Therefore, the
mechanism of the propanolysis of arenesulfonyl chlorides
4 | EXPERIMENTAL
Kinetics of solvolysis were spectrophotometrically studied
under pseudo‐first‐order conditions with respect to the
nucleophile on a Cary 1E UV‐Vis spectrophotometer, in
a thermostated quartz cuvette at constant temperature in
the temperature range 303.0‐323.0 K. Kinetic data were
confirmed by parallel experimentation. Observed rate
constants were calculated fitting the linear form of the
first‐order rate equation to kinetic data by linear least
squares method; the reported uncertainties are those
resulting from the fit.

IAZYKOV ET AL.
9 of 10
Solvents were thoroughly purified and dried.
ORCID
Benzenesulfonyl chloride, 4‐Br‐benzenesulfonyl chloride,
4‐Cl‐benzenesulfonyl chloride, 3‐NO2‐benzenesulfonyl
chloride, and 4‐NO2‐benzenesulfonyl chloride were pur-
chased from Sigma‐Aldrich and recrystallized from hexane
prior to their use. 4‐t‐Bu‐benzenesulfonyl chloride, m.
p. = 81.5‐82°C; 2,4,6‐Me3‐benzenesulfonyl chloride, m.
p. = 56.5‐57°C; 2,4,6‐Et3‐benzenesulfonyl chloride, (oil);
2,4,6‐i‐Pr3‐benzenesulfonyl chloride, m.p. = 96‐98°C; 2‐
Mykyta Iazykov http://orcid.org/0000-0001-9994-9096
Moisés Canle http://orcid.org/0000-0002-4814-7795
J. Arturo Santaballa http://orcid.org/0000-0003-0593-8009
Ludmila Rublova http://orcid.org/0000-0002-2129-9510
REFERENCES
[1] I. M. Gordon, H. Maskill, M. F. Ruasse, Chem. Soc. Rev. 1989,
18, 123.
Me‐benzenesulfonyl chloride, m.p.
= 10°C; 4‐Me‐
benzenesulfonyl chloride, m.p. = 70‐71°C; 2,4‐Me2‐
benzenesulfonyl chloride, m.p. = 33.5‐34°C; 2,5‐Me2‐
benzenesulfonyl chloride, m.p. = 20°C; 2‐Me‐5‐t‐Bu‐
[2] D. N. Kevill, M. J. D0 Souza, J. Chem. Res. S, 2008, 61.
[3] F. E. Jenkins, A. N. Hambly, Aust. J. Chem. 1961, 14, 190.
[4] B. Rossall, R. E. Robertson, Can. J. Chem. 1971, 49, 1441.
benzenesulfonyl
chloride,
(oil);
2,6‐Me2‐4‐t‐Bu‐
[5] I. S. Koo, T. W. Bentley, D. H. Kang, I. Lee, J. Chem. Soc., Perkin
Trans. 1991, 2, 175.
benzenesulfonyl chloride m.p. = 66‐67°C; 2,4,6‐(OMe)3‐
benzenesulfonyl chloride m.p. = 134‐136°C and 2,3,5,6‐
Me4‐benzenesulfonyl chloride m.p. = 97‐101°C were pre-
pared from the corresponding benzene derivatives as
described by Cremlyn.[44]
[6] G. Cevasco, A. Piatek, S. Thea, Org. Lett. 2011, 13, 668.
[7] H. K. Hall Jr., J. Am. Chem. Soc. 1956, 78, 1450.
[8] E. C. F. Ko, R. E. Robertson, J. Am. Chem. Soc. 1972, 94, 573.
[9] R. M. Forbes, H. Maskill, J. Chem. Soc., Chem. Commun.
1991, 854. http://pubs.rsc.org/en/content/articlelanding/1991/
c3/c39910000854#!divAbstract
4.1 | Sulfochlorination of substituted
[10] A. R. Haughton, R. M. Laird, M. J. Spence, J. Chem. Soc., Perkin
Trans. 1975, 2, 637.
benzenes
Under constant stirring (T = 273.0 K), 1 mole of hydro-
carbon, dissolved in 450 mL of an inert solvent (CHCl3,
CCl4, hexane), was added to crystalline NaCl (1 mole).
Then, chlorosulfonic acid (5 moles) was slowly added
dropwise over half an hour. After 3‐4 hours, the reaction
mixture was poured onto ice, treated with chloroform,
and the extract dried over CaCl2 or Na2SO4, and filtered.
The filtrate was evaporated under vacuum. The resulting
sulfonyl chloride was distilled under vacuum (2‐5 mm
Hg) with a fractionating column; the middle fraction
was collected and recrystallized from hexane, with a
yield of 65‐70%.
2‐Me‐5‐NO2‐benzenesulfonyl chloride, m.p. = 44‐46°C;
2,4‐Me2‐5‐NO2‐benzenesulfonyl chloride m.p. = 74.5‐
75.5°C and 2,4,6‐Me3‐3‐NO2‐benzenesulfonyl chloride,
m.p. = 60‐61°C; were synthesized analogously, but at a
higher temperature (313‐323 K). The obtained yield was
60‐65%. Melting points correspond to those available in
the literature.[45] The structure and purity of the obtained
compounds were confirmed by NMR, see Supporting Infor-
mation. The reaction products were analyzed using NMR,
X‐ray, and UV spectroscopy.
[11] A. Arcoria, F. P. Ballistreri, E. Spina, G. A. Tomaselli, E.
Maccarone, J. Chem. Soc., Perkin Trans. 1988, 2, 1793.
[12] F. P. Ballistreri, A. Cantone, E. Maccarone, G. A. Tomaselli, M.
Tripolone, J. Chem. Soc., Perkin Trans. 1981, 2, 438.
[13] E. Ciuffarin, L. Senatore, M. Isola, J. Chem. Soc., Perkin Trans.
1972, 2, 468.
[14] L. Senatore, L. Sagramora, E. Ciuffarin, J. Chem. Soc., Perkin
Trans. 1974, 2, 722.
[15] T. W. Bentley, R. O. Jones, J. Phys. Org. Chem. 2007, 20, 1093.
[16] L. C. Manege, T. Ueda, M. Hojo, M. Fujio, J. Chem. Soc., Perkin
Trans. 2 1998, 9, 1961.
[17] D. N. Kevill, B. C. Park, K. H. Park, M. J. D0Souza, L. Yaakoubd,
S. L. Mlynarski, J. B. Kyong, Org. Biomol. Chem. 2006, 4, 1580.
[18] O. Rogne, J. Chem. Soc. (B) 1969, 663.
[19] B. C. Lee, I. J. Lee, Korean Chem. Soc. 1980, 24, 342.
[20] T. W. Bentley, R. O. Jones, D. H. Kang, S. Koo, J. Phys. Org.
Chem. 2009, 22, 799.
[21] S. R. Kim, H. Choi, J. K. Park, I. S. Koo, H. J. Koh, Bull. Korean
Chem. Soc. 2014, 35, 51.
[22] Z. H. Ryu, S. W. Lee, M. J. D0Souza, L. Yaakoubd, S. E. Feld, D.
N. Kevill, Int. J. Mol. Sci. 2008, 9, 2639.
[23] S. Yamabe, G. Zeng, W. Guan, S. Sakaki, J. Comput. Chem.
2014, 35, 1140.
ACKNOWLEDGEMENTS
[24] T. W. Bentley, Int. J. Mol. Sci. 2015, 16, 10601.
Authors gratefully acknowledge EU financial support for
the mobility of MI to the UDC within the trans‐European
mobility Erasmus Mundus action TEMPO (372283‐1‐
2012‐1‐PT‐ERA MUNDUS‐EMA21).
[25] T. W. Bentley, H. Choi, I. S. Koo, D. N. Kevill, J. Phys. Org.
Chem. 2017, 30, e3585.
[26] M. L. Tonnet, A. N. Hambly, Aust. J. Chem. 1971, 24, 703.

10 of 10
IAZYKOV ET AL.
[27] M. Mikozajczyk, M. Gajl, W. Reimschtisel, Tetrahedron Lett.
1975, 16, 1325.
[40] C. Reichardt, Solvents and Solvent Effects in Organic Chemistry,
John Wiley & Sons 2006.
[28] F. E. Jenkins, A. N. Hambly, Aust. J. Chem. 1961, 14, 205.
[29] R. Hirata, N. Z. Kiyan, J. Miller, Quim. Nova 1997, 20, 238.
[41] A. Vrhovšek, O. Gereben, A. Jamnik, L. Pusztai, J. Phys. Chem.
B 2011, 115, 13473.
[42] H. Schaal, T. Häber, M. A. Suhm, J. Phys. Chem. A 2000, 104, 265.
[30] M. Iazykov, L. Rublova, L. M. Canle, J. A. Santaballa, J. Phys.
Org. Chem. 2017, 30.
[43] N. B. Chapman, M. G. Rodgers, J. Shorter, J. Chem. Soc. B
1968, 157.
[31] C. Hansch, A. Leo, Substituent Constants for Correlation
Analysis in Chemistry and Biology, John Wiley & Sons, New
York 1979.
[44] R. J. Cremlyn (Ed), Chlorosulfonic Acid a Versatile Reagent,
RSC, Cambridge 2002.
[32] L. Liu, Q. X. Guo, Chem. Rev. 2001, 101, 673.
[45] C. M. Suter, The Organic Chemistry of Sulfur, Tetracovalent Sul-
fur Compounds, John Wiley & Sons, New York 1948.
[33] K. A. Connors, Chemical Kinetics: The Study of Reaction Rates in
Solution, VCH, New York 1990.
[34] C. Ouvrard, M. Berthelot, T. Lamer, O. Exner, J. Chem. Inf.
Comput. Sci. 2001, 41, 1141.
SUPPORTING INFORMATION
Additional Supporting Information may be found online
in the supporting information tab for this article.
[35] R. Schmid, V. N. Sapunov, Non‐Formal Kinetics. In Search for
Chemical Reaction Pathways, Verlag Chemie, Weinheim 1982.
[36] L. Rubleva, V. Levandovsky, N. Yazikov, Visnyk of the Lviv
University. Series Chemistry. 2012, 53, 272.
How to cite this article: Iazykov M, Canle M,
Santaballa JA, Rublova L. Propanolysis of
arenesulfonyl chlorides: Nucleophilic substitution
at sulfonyl sulfur. J Phys Org Chem. 2017;e3753.
https://doi.org/10.1002/poc.3753
[37] I. S. Koo, T. W. Bentley, G. Llewellyn, K. Yang, J. Chem. Soc.,
Perkin Trans. 1991, 2, 1175.
[38] M. Charton, J. Am. Chem. Soc. 1975, 97, 1552.
[39] M. Iazykov, L. M. Canle, J. A. Santaballa, L. Rublova, Int. J.
Chem. Kinet. 2015, 47, 744.