Molecular structure and conformations of 2-nitrobenzenesulfonyl fluoride: Gas-phase electron diffraction and quantum chemical calculations study

Article abstract of DOI:10.1016/j.molstruc.2009.12.005

The molecular structure and conformational properties of 2-nitrobenzenesulfonyl fluoride, 2-NO₂-C₆H₄SO₂F, have been studied by gas-phase electron diffraction (GED) and quantum chemical methods (B3LYP/6-311+G and MP2/6-31G). Quantum chemical calculations predict the existence of three conformers for 2-NO₂-C₆H₄SO₂F each of them possesses C₁ symmetry. Conformer I, in which the S-F bond of the SO₂F group is nearly perpendicular to the plane of benzene ring, is predicted to be most favored. Conformer II, in which the S-F bond is situated in opposite direction with reference to the NO₂ group, possesses intermediate energy (Δ_1-2 = 0.73 kcal/mol (B3LYP), or 0.71 kcal/mol (MP2)), and conformer III with the S-F bond tilted to the NO₂ group possesses the higher energy (Δ_1-3 = 1.58 kcal/mol (B3LYP), or 1.47 kcal/mol (MP2)). The analysis of the GED intensities was carried out assuming the vapour consists of three conformers. In was obtained the conformer I dominates in vapour over solid 2-NO₂-C₆H₄SO₂F at T = 383(5) K. The conformer III concentration was found to be negligible. In dominant conformer I the S-F bond is bent slightly towards the nitro group (φ(C-C-S-F) = 84(8)°), and the torsional angle of the nitro group with respect to the benzene ring φ(C-C-N-O) equals 125(4)°. The conformation properties were determined by the potential energy surface analysis. The relative stability of conformers is discussed.

Full text of DOI:10.1016/j.molstruc.2009.12.005

Journal of Molecular Structure 978 (2010) 97–103
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Molecular structure and conformations of 2-nitrobenzenesulfonyl fluoride:
Gas-phase electron diffraction and quantum chemical calculations study
c
a
a
Vjacheslav M. Petrov a, Georgiy V. Girichev b, , Heinz Oberhammer , Nina I. Giricheva , Anna V. Bardina ,
*
Valentina N. Petrova b, Sergey N. Ivanov a
a Ivanovo State University, Ivanovo 153460, Russia
b Ivanovo State University of Chemistry and Technology, Ivanovo 153460, Russia
c Institut für Physikalische und Theoretische Chemie, Universität Tübingen, 72076 Tübingen, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
The molecular structure and conformational properties of 2-nitrobenzenesulfonyl fluoride, 2-NO2-
C6H4SO2F, have been studied by gas-phase electron diffraction (GED) and quantum chemical methods
(B3LYP/6-311+G** and MP2/6-31G**). Quantum chemical calculations predict the existence of three con-
formers for 2-NO2-C6H4SO2F each of them possesses C1 symmetry. Conformer I, in which the S–F bond of
the SO2F group is nearly perpendicular to the plane of benzene ring, is predicted to be most favored. Con-
former II, in which the S–F bond is situated in opposite direction with reference to the NO2 group, pos-
Received 20 November 2009
Accepted 2 December 2009
Available online 22 January 2010
Keywords:
2-Nitrobenzenesulfonyl fluoride
Geometric structure
Conformer
Gas-phase electron diffraction
Mass-spectrometry
sesses intermediate energy (DE1–2 = 0.73 kcal/mol (B3LYP), or 0.71 kcal/mol (MP2)), and conformer III
with the S–F bond tilted to the NO2 group possesses the higher energy (
or 1.47 kcal/mol (MP2)).
DE1–3 = 1.58 kcal/mol (B3LYP),
The analysis of the GED intensities was carried out assuming the vapour consists of three conformers.
In was obtained the conformer I dominates in vapour over solid 2-NO2-C6H4SO2F at T = 383(5) K. The con-
former III concentration was found to be negligible. In dominant conformer I the S–F bond is bent slightly
towards the nitro group (/(C–C–S–F) = 84(8)°), and the torsional angle of the nitro group with respect to
the benzene ring /(C–C–N–O) equals 125(4)°.
Quantum chemical calculations
The conformation properties were determined by the potential energy surface analysis. The relative
stability of conformers is discussed.
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
methyl-substituted sulfonyl fluorides find an application as possi-
ble therapeutic agents in Alzheimer’s disease. The use of these
The reactions of aromatic sulfonyl derivatives, in particular, sul-
fonyl halides have played an important role in development of
many fundamental concepts on which the modern organic chemis-
try is based, e.g. the reaction mechanisms, the neighboring group
effect, the solvent effects on reactivity [1]. The greatest application
among sulfonyl halides belongs to sulfonyl chlorides, which widely
applied as the initial species for the synthesis of the dyes, deter-
gents, high-temperature polymers and pharmaceutical agents, as
the electrophilic reagents and the sources of Ts-radicals, etc.
[1,2]. Sulfonyl fluorides, as opposed to chlorides, show the charac-
teristic properties, as low reactivity and stability to the hydrolysis
in the water, high volatility, that allows to use them as the volatile
forms at the analysis by gas–liquid chromatography. Besides, the
sulfonyl fluorides display rather high biological activity as a basis
for the enzymatic inhibition. Thus, the different nitro- and
agents in the context of structure/activity relationships is dis-
cussed in the literature [3].
Data on the geometrical and electronic structure as well as the
conformational properties of this molecule are necessary for dee-
per understanding the mechanism of enzymatic inhibition under
sulfonyl fluorides action, based on the known principle of comple-
mentarity substrate/enzyme.
The present study continues a systematic investigation of struc-
tural and conformational properties of methyl substituted ben-
zenesulfonyl halides [4–7].
Infrared and NMR spectra of various substituted benzenesulfo-
nyl halides have been reported in the literature [8]. These data,
however, do not provide any information about the structural or
conformational properties of these compounds. The X-ray studies
carried out for 2-nitrobenzenesulfonyl chloride showed that 2-
NO2-C6H4SO2Cl exists in the crystal phase as single conformer with
near perpendicular orientation of the S–Cl bond with reference to
the plane of benzene ring [9,10].
* Corresponding author.
E-mail address: girichev@isuct.ru (G.V. Girichev).
0022-2860/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2009.12.005

98
V.M. Petrov et al. / Journal of Molecular Structure 978 (2010) 97–103
Table 2
The present work is devoted to studying the mutual influence of
Mass spectrum of the saturated vapour of ortho-nitrobenzenesulfonylfluoride, 2-NO2-
C6H4SO2F, recorded at Uioniz = 50 V simultaneously with the diffraction pattern
registration.
NO2 and SO2F groups in ortho-position where strong steric interac-
tions between these groups are expected.
Ion
m/e a.u.
Abundance (relative to [SO2]+, %)
[SO2]+
64
76
83
96
108
170
186
205
100
32.4
63.5
93.2
12.2
4.1
2. Experimental
[C6H4]+
[SO2F]+
The species 2-NO2-C6H4SO2F was prepared from a commercial
sample of 2-nitrobenzenesulfonyl chloride, 2-NO2-C6H4SO2Cl.
Chlorine was replaced by fluorine by heating 2-NO2-C6H4SO2Cl in
water solution with fivefold molar excess of KFꢀHF [11]. The 2-
NO2-C6H4SO2F was washed from hydrochloric acid then filtered,
dried and re-crystallized twice from the solvent hexane/propane-
2-ol (80/20) until a sample with a melting point of 361.0 (0.5) K
was obtained (literature melting point is 362 K [12]. The gas–liquid
chromatographic analysis has demonstrated the absence of meta-
and para-isomers.
[C5H4S]+
[C6H4S]+
[C6H4NO2SO]+
[C6H4NO2SO2]+
[C6H4NO2SO2F]+
2.0
32.4
L = 598 mm
The electron diffraction patterns were recorded with the appara-
tus described previously [13]. The effusion cell of molybdenum with
a cylindrical nozzle of 0.6 ꢁ 1.6 mm size (diameter ꢁ length) was
used for evaporation of the samples at 383(5) K. The temperature
of the effusion cell was measured by a thermocouple W/Re—5/20.
The electron wavelength was obtained from diffraction patterns of
polycrystalline ZnO. The mass spectra of the vapor were recorded
simultaneously with the registration of the diffraction pattern.
The heaviest ion was the monomeric parent ion. The details of the
combined gas electron diffraction and mass spectrometric experi-
ment (GED/MS) are listed in Table 1. The mass spectrum shown in
Table 2 demonstrates that the vapor of the investigated compound
consists of only one species with the stoichiometry NO2-C6H4SO2F
and the detectable amount of volatile impurities in the sample is
absent.
L = 338 mm
Δ
sM(s)
0
2
4
6
8
10 12 14 16 18 20 22 24 26 28 30 32
s, Å-1
Optical densities of the plates were measured by a computer
controlled MD-100 microdensitometer [14]. For the microphoto-
metric measurements 6 plates for each, long and short camera dis-
tance, were used. A rectangular area of about 130 ꢁ 15 mm2 was
scanned along the diagonal of the plates. The data array for the
diagonal consisted of 33 lines, 1299 points each. The step width
along a scan line was 0.1 mm, and the distance between the lines
was about 0.28 mm. The scanning of the plates with ZnO diffrac-
tion patterns for calibration of the electron wavelength was done
with a step width of 0.0125 mm. The background functions G(s)
for the intensities I(s) of the long and short camera distances were
approximated by smooth lines. The analysis of the first and second
order derivatives of the G(s) functions were used to examine the
absence of oscillations in G(s), which could be close to the oscilla-
tions in the sM(s) function. No elimination of the frequency oscilla-
tions was done. The molecular intensities sM(s) were obtained in
the ranges 3.0–31.0 Åꢂ1 and 1.4–16.1 Åꢂ1 for the short and long
camera distance, respectively (Fig. 1). The molecular intensity
was calculated by the formula
Fig. 1. Experimental (dots) and theoretical (full line) molecular intensities sM(s)
and residuals for ortho-nitrobenzenesulfonylfluoride for the long (a) and short (b)
nozzle-to-plate distances.
3. Quantum chemical calculations
The structure optimizations and force field calculations were
performed with the DFT method B3LYP/6-311+G** and with the
ab initio approximation MP2/6-31G** using the GAUSSIAN 03 pro-
gram system [15]. In the first step the search for all possible stable
conformers was performed with the 2-dimensional scan of the
/(C2–C1–S–F) and /(C1–C2–N–O) torsional angles in steps of 20°
(for atom numbering see Fig. 2). The potential energy surface de-
rived with the B3LYP method (Fig. 3) shows the presence of three
conformers, all possessing C1 symmetry with neither S–F nor N–O
bond in the plane of the benzene ring. The structures of these con-
formers were fully optimized with the B3LYP and MP2 methods
(see Fig. 2). The torsional angles /(C2–C1–S–F) and /(C1–C2–N–
O), the relative energies and Gibbs free energies and the lowest
vibrational frequencies are given in Table 3. The structural param-
eters of three conformers are included in Table 4.
IðsÞ ꢂ GðsÞ
sMðsÞ ¼
ꢀ s:
GðsÞ
According to relative Gibbs free energies given in Table 3 (
0.60 kcal/mol (B3LYP/6-311+G**) or 0.64 kcal/mol (MP2/6-31G**),
and G°I–III = 1.45 kcal/mol (B3LYP/6-311+G**) or 1.40 kcal/mol
DG°I–II =
D
Table 1
(MP2/6-31G**)), conformer I should be prevailing with 62.2 mol.%
(B3LYP) or 63.0 mol.% (MP2) and also the concentration of conformer
II is significant with 28.4 mol.% (B3LYP) and 27.1 mol.% (MP2). At the
temperature of the GED experiment conformer III is predicted to pos-
sess an abundance of 9.4 mol.% (B3LYP) or 9.9 mol.% (MP2).
Conditions of the simultaneous GED/MS experiments.
ortho-Nitrobenzenesulfonyl fluoride
Nozzle-to-plate distance, mm
Electron beam current,
Accelerating voltage, kV
338
1.4
95.2
598
0.7
95.6
lA
Temperature of effusion cell, K
Ionization voltage, V
Exposure time, s
382(5)
50
384(5)
50
4. Structure analysis
90
65
Residual gas pressure, Torr
1.0ꢀ10ꢂ6
3.0–31.0
1.2ꢀ10ꢂ6
1.4–16.1
A conventional least squares analysis of sM(s) was carried out
using a modified version of KCED program [16]. The scattering
Scattering angles, Åꢂ1

V.M. Petrov et al. / Journal of Molecular Structure 978 (2010) 97–103
99
Fig. 2. Molecular models with atom numbering: (a) conformer I; (b) conformer II; (c) conformer III.
Table 3
Calculated relative energies and Gibbs free energies (kcal/mol) of the three stable
conformers of ortho-nitrobenzenesulfonylfluoride.
B3LYP/6-311+G**
Conformer I
Conformer II
Conformer III
8
a
/(C2–C1–S–F)
/(C1–C2–N–O3)
81.8
134.2
0.0
0.0
46
159.8
27.0
0.73
0.60
31
45.1
36.3
1.58
1.45
35
6
D
D
m
E, kcal/mol
a
G° , kcal/mol
4
II
1, cmꢂ1
MP2/6-31G**
/(C2–C1–S–F)
/(C1–C2–N–O3)
2
III
80.6
137.5
0.0
0.0
55
156.8
32.8
0.71
0.64
45
42.4
39.5
1.47
1.40
47
0
20º
40º
60º
80º
100º
120º
140º
160º
180º
D
D
m
E, kcal/mol
G° a, kcal/mol
1, cmꢂ1
I
a
At T = 383 K.
180º
160º
140º
120º
100º
80º
The following assumptions were made to describe the molecu-
60º
40º
lar geometry of each conformer: (1) C1 overall symmetry was as-
sumed for each conformers; (2) all atoms of the N–C6H4–S
fragment lie in the same plane; (3) all CPh–H bonds in the ring pos-
sess equal length and bisect the adjacent C–C–C angle; (4) differ-
ences between N@O, S@O bond lengths, between C–C bond
lengths as well as C–C–C bond angles in the benzene ring, and be-
tween O@NAC, O@SAC, O@SAF bond angles are constrained to cal-
culated values; (6) vibrational amplitudes were collected in 11
groups, including two groups for the distances involving the hydro-
gen atoms. The differences within each group were constrained to
calculated values. The molecular structures were constructed with
17 independent structural parameters for three conformers of 2-
NO2-C6H4SO2F (p1 to p17 in Table 4). In the LS-analysis the follow-
ing parameters were refined independently: 7 bond distances (C1–
C2, CPh–H, C1–S, C2–N, S–F, S@O, N@O), six bond angles (\C2–C1–
C6, \C1–S–F, \C1–S–O1, \O1–S–F, \C2–N–O3, \C1–C2–N), and
four torsion angles for the conformers I and II (/(C2–C1–S–F) and
/(C1–C2–N–O3). All parameters of the conformers II and III,
excluding the torsion angles, were tied to those of the conformer
I using the calculated differences.
On the first step of LS-analysis we assumed that the vapour con-
sisted of only one species – conformer I, or conformer II, or con-
former III. The theoretical intensities were calculated separately
for each conformer on the base of structural parameters (r, l) fixed
in LS-analysis at the values obtained by B3LYP/6-311+G**, and the
scale-factor was refined only. For each conformer the reasonable
agreement between experimental and theoretical functions sM(s)
had not been achieved (Rf = 16.5%, 24.4% and 19.9% for I, II and III
conformers correspondingly). Main reason of bad agreement is
the large differences between the calculated and experimental
S@O, S–F and S–C bond lengths.
20º
0º
180º
160º
140º
120º
100º
80º
b
II
A
I
60º
40º
20º
0º
B
III
20º
0º
40º 60º
80º 100º 120º 140º 160º 180º
C1-C2-N-O3
Fig. 3. Calculated potential energy surface (a), and constant energy contour map (b)
with conformers I, II, and III obtained by scanning along torsion angles C2–C1–S–F b
C1–C2–N–O3 for ortho-nitrobenzenesulfonyl fluoride.
functions of reference [17] were used for calculation of the theoret-
ical molecular intensities. The starting values for bond distances
and angles were taken from the B3LYP/6-311+G** calculations.
Vibrational corrections,
D
r = rh1 ꢂ ra, and the starting values for
vibrational amplitudes were derived from the B3LYP/6-311+G**
force field, using the curvilinear approach of Sipachev (program
SHRINK) [18].

100
V.M. Petrov et al. / Journal of Molecular Structure 978 (2010) 97–103
Table 4
Experimental and calculated structural parameters of ortho-nitrobenzenesulfonylfluoride, 2-NO2-C6H4SO2F, (distances in Å, angles in deg.).
Parameter
Conformer I
Conformer II
Conformer III
GED rh1
B3LYP 6-311+G** re
GED rh1
B3LYP 6-311+G** re
GED rh1
B3LYP 6-311+G** re
structure
structure
structure
structure
structure
structure
C–H
C1–C2
C2–C3
C3–C4
C4–C5
C5–C6
C1–C6
C–S
S–F
S–O1
S–O2
C–N
N–O3
N–O4
\C2–C1–C6
\C1–C2–C3
\C2–C3–C4
\C3–C4–C5
\C4–C5–C6
\C1–C6–C5
\C1–S–F
\C1–S–O1
\C1–S–O2
\O1–S–F
\O2–S–F
\O1–S–O2
\C2–C1–S
\C2–N–O3
\C2–N–O4
\O3–N–O4
\C1–C2–N
\C2–C1–S–F
\C1–C2–N–
O3
1.101(9)a p1
1.410(3) p2
1.398(3) (p2)
1.403(3) (p2)
1.402(3) (p2)
1.404(3) (p2)
1.404(3) (p2)
1.757(5) p3
1.527(5) p4
1.410(4) p5
1.414(4) (p5)
1.483(8) p6
1.212 (3) p7
1.209(3) (p7)
119.5(1) p8
120.7(1) (p8)
119.3(6) (p8)
120.6(9) (p8)
119.8(6) (p8)
120.1(1) (p8)
98.9(14) p9
110.4(5) p10
108.1(5) (p10
108.6(9) p11
106.5(9) (p11
121.9(17)
1.083
1.399
1.387
1.393
1.391
1.393
1.393
1.801
1.625
1.440
1.444
1.484
1.221
1.218
119.4
120.6
119.7
120.1
120.1
120.1
100.3
110.7
108.3
108.2
105.3
122.5
124.4
117.1
116.6
126.3
123.0
81.8
1.101(9)a (p1)
1.412(3) (p2)
1.399(3) (p2)
1.402(3) (p2)
1.401(3) (p2)
1.405(3) (p2)
1.405(3) (p2)
1.773(5) (p3)
1.554(5) (p4)
1.409(4) (p5)
1.409(4) (p5)
1.481(8) (p6)
1.212(3) (p7)
1.211(3) (p7)
118.9(1) (p8)
121.1(1) (p8)
119.4(6) (p8)
120.2(9) (p8)
120.1(6) (p8)
120.2(1) (p8)
94.6(14) (p9)
1.082
1.401
1.388
1.391
1.390
1.394
1.393
1.817
1.651
1.439
1.438
1.481
1.221
1.220
118.8
121.0
119.7
119.8
120.5
120.2
96.1
110.8
111.8
104.4
104.5
124.5
122.6
116.6
117.3
125.8
122.2
159.8
27.0
1.101(9)a (p1)
1.412(3) (p2)
1.400(3) (p2)
1.402(3) (p2)
1.401(3) (p2)
1.405(3) (p2)
1.404(3) (p2)
1.767(5) (p3)
1.533(5) (p4)
1.408(4) (p5)
1.415(4) (p5)
1.484(8) (p6)
1.209(8) (p7)
1.214(10) (p7)
119.1(1) (p8)
120.6(1) (p8)
119.7(6) (p8)
120.4(9) (p8)
119.8(6) (p8)
120.4(1) (p8)
97.0(14) (p9)
1.082
1.401
1.389
1.391
1.390
1.393
1.394
1.811
1.631
1.438
1.444
1.484
1.218
1.222
119.1
120.5
120.0
119.9
120.1
120.3
98.5
113.3
107.4
107.7
105.7
121.6
126.9
117.4
116.6
126.0
123.4
45.1
110.6(5) (p10
111.5(5) (p10
105.8(9) (p11
105.8(9) (p11
124.1(17)
)
)
)
)
113.0(5) (p10
107.1(5) (p10
108.9(9) (p11
106.9(9) (p11
121.0(17)
)
)
)
)
)
)
124.4(1) (p8)
116.5(5) p12
116.9(5) (p12
126.3(7)
123.1(1) p13
83.8(76) p14
122.7(1) (p8)
116.6(5) (p12
117.3(5) (p12
125.8(7)
127.0(1) (p8)
117.3(5) (p12
116.4(5) (p12
125.8(7)
)
)
)
)
)
122.2(1) (p13
)
123.5(1) (p13
45.1
)
147.2(86) p16
24.6(168) p17
125.1(41) p15
137.0
36.3
36.3
Mole fraction
Rf, %
0.74(6)
2.62
0.66
0.26(10)
0.30
0.0(6)
0.04
a
The total error limit in interatomic distances was estimated by formula
significant digit).
bErrors in determination of the mole fraction are calculated on the basis of analysis criterion Hamilton [19].
r = ((2.5rLS) rLS (in the units of last
2 + (0.002r)2)1/2, total error in the angles was taken to be equal 3
On the second step of LS-analysis the theoretical function sM(s)
for individual conformers was adjusted to experimental one vary-
ing the all mentioned above parameters excluding the torsion an-
gles. The differences between experimental and theoretical
functions f(r) were observed in the conformation dependent region
2.45–5.20 Å only. The value Rf was equal 3.53%, 9.30% and 8.70% for
I, II and III conformers correspondently. These calculations testify
to the first conformer predominates in the vapour at T = 383 K.
On the third step of LS-analysis the theoretical function sM(s) was
calculated taking into account the contribution of the all three con-
5. Discussion
5.1. Conformational vapor composition and conformation properties
On diagram in Fig. 5 the refinement of the conformational vapor
composition is illustrated. Each point on this diagram corresponds
to the solution (refined structures, vapor compositions and Rf) ob-
tained by LS-analysis described above as the third step.
The bounded by solid curve points satisfy to Hamilton [19] cri-
teria at the significance level 0.05 (m = 26, n = 429). The best value
Rf = 2.62%, which corresponds to the optimal conformational vapor
composition 76% conformer I, 24% conformer II, and 0% conformer
III, is given on diagram as the circle.
formers. The coefficients v1, v2 and v3 corresponded to conformer
mole fractions were changed discretely in the range from 0.60–1.00,
0.00–0.40 and 0.00–0.30 correspondingly, while the structural
parameters of conformers were refined in the LS-analysis excepting
torsional angles in the conformer III. The minimal Rf = 2.62% was
The standard quantum chemical calculations at the B3LYP/6-
311+G** theory level was performed to predict the vapor composi-
tion at the temperature 383 K. The vapor composition (in mole
achieved for the values of mole fractions
3 = 0.00. Six correlation coefficients had an absolute value larger
than 0.7: p2/p8 = ꢂ0.91, p2/p14 = 0.74, p4/p5 = 0.80, p6/p17 = ꢂ0.70,
12/p17 = 0.78, u4/p11 = 0.94. The experimental and calculated geo-
v1 = 0.76, v2 = 0.24,
v
fraction)
v1 = 0.622, v2 = 0.284 and v3 = 0.094 calculated by Gibbs
free energy (Table 3) and marked on the diagram by asterisk, dif-
fers significantly from the composition obtained by LS-analysis.
The Gaussian 03 program calculates the vibration contribution of
the Gibbs free energy at the temperature different from 0 K sum-
ming an infinite large progression of vibrational levels of the
molecule.
The potential energy surface analysis (see Figs. 3 and 6) sug-
gests that this approach overestimates the relative concentration
of conformer III significantly. The more realistic estimation of the
p
metric parameters of all three conformers are listed in Table 4. The
interatomic distances, vibrational amplitudes and vibrational cor-
rections for the prevailing conformer I are listed in Table 5 and those
for the minor conformers II and III are given as Supplementary Mate-
rial (Tables S1and S2). The experimental radial distribution function,
which is derived by Fourier transformation of the experimental
intensities, is shown in Fig. 4.

V.M. Petrov et al. / Journal of Molecular Structure 978 (2010) 97–103
101
Table 5
Table 5 (continued)
Experimental interatomic distances, experimental and calculated vibrational ampli-
tudes and vibrational corrections (without non-bonded distances involving hydrogen
atoms) for ortho-nitrobenzenesulfonylfluoride, 2-NO2-C6H4SO2F, (conformer I).
Parameter
ra
lexp.
lcalc.
D
r = rh1 ꢂ ra
No. group
C3–O2
C5–O1
C4–F
C4–O2
C4–O1
O4–O2
4.980(4)
4.979(7)
5.006(13)
5.099(6)
5.241(5)
5.314(34)
0.167(3)
0.139(3)
0.190(3)
0.144(3)
0.120(3)
0.493(3)
0.154
0.126
0.177
0.131
0.107
0.480
0.020
0.012
0.026
0.027
0.022
0.073
9
9
9
9
9
9
Parameter
ra
lexp.
lcalc.
D
r = rh1 ꢂ ra
No. group
C3–H
N–O3
N–O4
C2–C3
C5–C4
C3–C4
C1–C6
C6–C5
C1–C2
S–O1
1.096(4)a
1.211(1)
1.208(1)
1.396(1)
1.401(1)
1.402(1)
1.402(1)
1.403(1)
1.408(1)
1.409(1)
1.413(1)
1.481(3)
1.526(1)
1.755(1)
2.155(1)
2.292(2)
2.296(3)
2.383(5)
2.354(5)
2.412(3)
2.425(2)
2.432(5)
2.423(3)
2.428(2)
2.435(2)
2.440(3)
2.465(7)
2.493(9)
2.538(3)
2.569(3)
2.604(3)
2.681(2)
2.750(34)
2.795(3)
2.798(4)
2.799(1)
2.808(3)
2.815(7)
3.359(17)
2.897(20)
2.964(9)
3.065(47)
3.100(9)
3.124(19)
3.214(3)
3.310(16)
3.312(23)
3.359(8)
3.409(12)
3.482(40)
3.569(32)
3.734(3)
3.797(8)
3.802(4)
3.881(4)
3.998(2)
4.078(2)
4.068(24)
4.190(12)
4.201(6)
4.268(5)
4.296(7)
4.468(7)
4.517(12)
4.519(21)
4.522(19)
4.543(7)
4.542(4)
4.572(7)
4.584(9)
4.640(29)
4.900(5)
4.954(5)
0.079(1)
0.042(1)
0.042(1)
0.043(0.4)
0.043(0.4)
0.043(0.4)
0.043(0.4)
0.043(0.4)
0.044(0.4)
0.033(0.4)
0.033(0.4)
0.050(0.4)
0.046(0.4)
0.062(1)
0.041(2)
0.055(2)
0.056(2)
0.064(2)
0.066(2)
0.048(2)
0.048(2)
0.048(2)
0.048(2)
0.048(2)
0.048(2)
0.058(2)
0.051(2)
0.087(2)
0.059(2)
0.077(2)
0.066(2)
0.060(3)
0.227(3)
0.055(3)
0.056(3)
0.068(3)
0.055(3)
0.091(3)
0.126(3)
0.107(3)
0.144(3)
0.292(1)
0.069(1)
0.224(1)
0.109(1)
0.134(1)
0.145(1)
0.126(1)
0.136(1)
0.308(1)
0.178(1)
0.075(4)
0.128(4)
0.077(4)
0.161(4)
0.078(4)
0.084(4)
0.303(4)
0.151(4)
0.120(4)
0.081(4)
0.143(2)
0.076(2)
0.157(2)
0.165(2)
0.233(2)
0.225(2)
0.063(2)
0.116(2)
0.115(2)
0.208(2)
0.119(3)
0.119(3)
0.075
0.039
0.039
0.046
0.045
0.045
0.046
0.046
0.046
0.036
0.036
0.053
0.048
0.055
0.049
0.063
0.064
0.072
0.074
0.056
0.056
0.056
0.056
0.056
0.056
0.066
0.059
0.095
0.067
0.085
0.074
0.068
0.235
0.063
0.063
0.076
0.063
0.098
0.165
0.115
0.152
0.300
0.076
0.232
0.117
0.142
0.153
0.134
0.144
0.317
0.186
0.067
0.120
0.069
0.153
0.068
0.074
0.293
0.141
0.110
0.071
0.133
0.086
0.167
0.175
0.243
0.235
0.072
0.126
0.125
0.218
0.106
0.106
0.005
0.001
0.001
0.002
0.001
0.001
0.002
0.001
0.002
0.001
0.001
0.002
0.001
0.002
0.005
0.004
0.004
0.004
0.004
0.006
0.006
0.005
0.004
0.005
0.005
0.006
0.004
0.006
0.007
0.005
0.004
0.007
ꢂ0.010
0.007
0.007
0.008
0.006
0.019
ꢂ0.001
0.020
ꢂ0.003
ꢂ0.040
0.016
ꢂ0.014
0.007
0.012
0.019
0.032
0.032
0.079
0.010
0.013
0.003
0.013
0.010
0.014
0.015
0.059
0.009
0.027
0.016
0.005
0.023
0.020
0.025
ꢂ0.0001
0.008
0.018
0.031
0.034
0.057
0.024
0.020
1
1
1
2
2
2
2
2
2
2
2
2
2
3
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
6
6
6
6
6
6
6
6
6
7
7
7
7
7
7
7
7
7
7
8
8
8
8
8
8
8
8
8
8
9
9
a
rLS in brackets.
vapor composition could be derived taking into account the depth
of the potential well corresponded to the conformer III.
In Fig. 3b, the extremal for the transition ‘‘conformer II ? saddle
point A ? conformer I ? saddle point B ? conformer III” is shown.
In Fig. 6, the profile of potential energy surface along this path
II ? A ? I ? B ? III is given as the potential function of the inter-
nal rotation of group SO2F around the bond S–C1. The potential
function was calculated scanning the value /(C2–C1–S–F) and
refining all other geometrical parameters including torsion angle
/(C1–C2–N–O3).
Both computational methods B3LYP/6-311+G** and MP2/6-31G**
predict very similar potential function with three minima. The barrier
between conformers I and III is 1.79 kcal/mol (B3LYP/6-311+G**) or
1.85 kcal/mol (MP2/6-31G**) and were measured from the energy
minima. The barrier between conformers I and II is 2.11 kcal/mol
(B3LYP/6-311+G**) or 2.61 kcal/mol (MP2/6-31G**). The conformer
I possesses the highest stability. The relative energy of conformer III
testifies to its lowest stability. These results don’t contradict the con-
former concentrations obtained by GED.
The lowest vibrational mode m1 for all three conformers corre-
sponds to the mixed torsion movement of two groups SO2F and
NO2. The energy of the saddle points A and B exceed the thermal
energy RT at the temperature of GED experiment (dots line in
Fig. 6) by two times. It means that small relative number of the
molecules overcome the potential barriers.
In harmonic approximation the potential well of the conformer
III contains only four energy levels of vibrational mode m1. If the en-
ergy of conformer is higher than the energy barrier EA, the vibra-
tion state of molecule could be considered as the vibration state
of conformer I possessed a very strong anharmonicity rather than
as the exited vibrational state of the conformer III.
S–O2
C2–N
S–F
C1–S
O3–O4
C2–O4
C2–O3
F–O1
F–O2
C2–C4
C6–C2
C5–C3
C6–C4
C1–C5
C1–C3
C3–N
O1–O2
C1–F
C1–N
C1–O2
C1–O1
C6–S
O3–O1
C2–C5
C1–C4
C2–S
C6–C3
C6–O2
C3–O3
N–O1
C1–O3
F–O3
C2–O1
S–O3
N–S
C2–F
C6–F
C3–O3
C1–O4
O4–O1
N–F
C4–N
C6–O1
C6–N
C2–O2
C5–S
The conformer composition in equilibrium mixture calculated
on the base
of conformer III concentration due to taking into account the infi-
nite large progression of vibrational levels (statistical sum of m1
DG° (383 K) values (Table 3) gives the highest limit
mode Qvib
for other vibrational modes but for mode
vibrational levels only (the value of Qvib
(
m
1) = 7.8 at T = 383 K). If we keep the statistical sum
1 take into account four
1) equals 3.1) conformer
m
m
(
composition is changed from 62.2/28.4/9.4 to 66.2/29.8/4.0 mol.%.
This composition is marked by square on the diagram in Fig. 5 and
are close to the conformational composition obtained by GED.
We carried out LS-analysis with the fixed conformer composi-
tion 66.2/29.8/4% varying all 17 geometrical parameters and 9
amplitude groups (Rf = 2.64%). The value of the structural parame-
ters obtained in this refinement are very close to the parameters
corresponded to best Rf equals 2.62% (the discrepancy is about
0.002 Å in bond distances and 0.1–0.2° in bond angles).
C3–S
S–O4
C4–O4
C5–O2
C5–N
C6–O3
C3–O1
C3–F
C5–F
O3–O2
N–O2
C4–S
C4–O3
C6–O4
F–O4
5.2. Structural parameters of conformers
The calculated structural parameters of three conformers are
very close to the experimental parameters excluding bond
lengths involving sulphur, especially the S–F and S@O bonds. It
is well known that calculations with relatively small basis sets
C5–O4
C5–O3

102
V.M. Petrov et al. / Journal of Molecular Structure 978 (2010) 97–103
f(r)
f(r)
0
2
4
6
8
r, Å
Fig. 4. Experimental (dots) and theoretical (full line) radial distribution function for
ortho-nitrobenzenesulfonyl fluoride and residual curve for optimal mixture.
Fig. 6. Calculated potential functions for internal rotation around the C1–S bond in
orthonitro-benzenesulfonylfluoride.
In conformer III no one bond of group SO2F lies in near perpen-
dicular plane to benzene ring. The larges torsion angle O1–S–C–C is
equal 69°. The energy of
2.94 kcal/mol is lower than sum of similar interactions mentioned
above in conformer II. But in conformer III the strong interaction of
p(C–C) ? r*(S–O1) interaction is
Fig. 5. The ternary diagram of conformer composition. The bounded by solid curve
points satisfy to Hamilton criteria at the significance level 0.05. The circle
corresponds to best value Rf = 2.62%. The asterisk and the square mark the vapor
compositions calculated using standard and corrected vibrational statistical sum
correspondingly (see the text).
p(C–C) ? r*(S–F) with energy 4.0 kcal/mol occur in spite of the
torsion angle F–S–C–C value in 45° only.
Thus the analysis of the orbital interactions between
r* orbitals
of SO2F fragment and p-system of benzene ring allow to conclude
the conformer I can be more stable in comparison with the con-
formers II and III, but can’t say about any preference for II in com-
parison with conformer III.
Besides the orbital interaction the steric interaction between
groups SO2F and NO2 was studied in each conformer. The steric
interaction was found to be higher in conformer II.
The analysis of C1–C2, C1–S and C2–N bond order shows the
C1–C2 bond order are the same in all conformers while the bond
C1–S is stronger in conformer I, and the bond C2–N1 is stronger
in conformer II.
overestimate S–X bond lengths if X is an electronegative ele-
ment. The addition of diffuse functions to the basis set makes
the agreement between theory and experiment closer but does
not solve the problem completely (Table 4). A reasonable agree-
ment was obtained between the experimental and calculated
values of vibrational amplitudes (Table 5 and Supplementary
materials S1 and S2).
The NBO-analyses was carried out studying the orbital and steric
interactions, which affect the stability of conformers. It was found
the interaction between
*(S–O) antibonding orbitals occur.
The conformer I possesses the largest value of orbital effect
(C–C) + *(S–F) = 7.09 kcal/mol). In conformer I the torsion angle
p
(C–C) bonding orbitals and
r
*(S–F) and
Perhaps the prevailing of conformer II over conformer III is con-
nected with lower angle strain C2–C1–S in conformer II due to the
value of this bond angle is close to 120°, whereas this bond angle in
conformer III equals to 127°.
r
(p
r
between S–F bond and the plane of benzene ring is about 82°, and
According to the calculations all conformers are flexible and pos-
it leads to remarkable orbital interaction.
sess approximately equal electric dipole moments (
lI = 7.37 D,
In conformer II the orbital interaction exists between
p(C–C) ?
l
II = 7.59 D, III = 7.24 D; B3LYP/6-311+G**), but they have different
l
r
*(S–O2) and (C–C) ? *(S–O1). The energy of these interactions
p
r
distribution of electrostatic potentials and steric accessibility of O
and F atoms of SO2F group. Probably these factors affect the reactivity
difference of the conformers. Due to the low values of conformational
(2.55 kcal/mol and 1.42 kcal/mol correspondingly) correlate with
the value of torsion angles O2–S–C–C ꢃ90°, and O1–S–C–C ꢃ51°.

V.M. Petrov et al. / Journal of Molecular Structure 978 (2010) 97–103
103
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Acknowledgements
We thank the Deutsche Forschungsgemeinschaft and Russian
Fond of Basic Researches for financial support of the Russian-Ger-
man Cooperation (grants DFG 413 RUS 113/69/0-7 and RFBR 09-
03-91341_HHBO_a). The labor-consuming calculations derived
from the referee comments were made with the computing sup-
port by grant RFBR 09-03-00796_a.
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Appendix A. Supplementary data
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H.P. Hratchian, J.B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann,
O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala,
K. Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski,
S. Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck,
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J. Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi,
R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara,
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3224.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.molstruc.2009.12.005.
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