Quantum-chemical study of the structure of N-substituted p-quinonimines and their reactions with hydrogen halides

Article abstract of DOI:10.1023/B:RUJO.0000045185.66716.6c

Quantum-chemical calculations and X-ray diffraction data for a series of N-substituted p-quinon-imines showed that the PM3 method is the most suitable for determination of geometric parameters of these compounds. Moreover, it can be used to predict the site of addition of chlorine and bromine in the hydrohalogenation reaction.

Full text of DOI:10.1023/B:RUJO.0000045185.66716.6c

Russian Journal of Organic Chemistry, Vol. 40, No. 7, 2004, pp. 962–965. Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 7, 2004,
pp. 1003–1006.
Original Russian Text Copyright © 2004 by Avdeenko, Konovalova, Burmistrov, Toropin, Vakulenko.
Quantum-Chemical Study of the Structure
of N-Substituted p-Quinonimines and Their Reactions
with Hydrogen Halides
A. P. Avdeenko1, S. A. Konovalova1, K. S. Burmistrov2,
N. V. Toropin2, and A. V. Vakulenko2
1 Donbass State Machine-Building Academy, ul. Shkadinova 72, Kramatorsk-13, 84313 Ukraine
e-mail: chimist@dgma.donetsk.ua
2 Ukrainian State University of Chemical Technology
Receied May 8, 2002
Abstract—Quantum-chemical calculations and X-ray diffraction data for a series of N-substituted p-quinon-
imines showed that the PM3 method is the most suitable for determination of geometric parameters of these
compounds. Moreover, it can be used to predict the site of addition of chlorine and bromine in the hydrohalo-
genation reaction.
AM1, and PM3) we made an attempt to find out which
of the above procedures is most appropriate for N-sub-
stituted p-quinonimines, namely for determination
of active centers in their molecules in nucleophilic
addition reactions.
Quantum-chemical methods are now widely used in
studies on the reactivity of organic compounds. There
are two main requirements to the level of approxi-
mation and choice of the calculation scheme. First, the
results of calculations should be consistent with the
corresponding experimental data, and second, the cal-
culations should not be expensive from the viewpoint
of computational time [1]. With the aid of MOPAC 6
software package which includes four semiempirical
quantum-chemical methods (MINDO/3, MNDO,
While analyzing the results obtained by any
quantum-chemical method, the relative rather than
absolute values are important. Therefore, the problem
was to choose such a procedure which would ensure
minimal deviations of the optimized geometric
Bu-t
Pr-i
Bu-t
Br
N
O
Cl
SN
O
Cl
CON
O
Bu-t
Pr-i
Bu-t
I
II
III
Cl
Cl
Me
Me
Me
TsN
O
Cl
SO2N
O
MeSO2N
NSO2Me
PhSO2ON
O
IV
V
VI
VII
Me
Me
Me
Me
Me
Me
Ph
PhCOON
O
Cl
SO2N
C
N
O
PhSO2N
C
N
O
Me
VIII
IX
X
1070-4280/04/4007-0962 © 2004 MAIK “Nauka/Interperiodica”

QUANTUM-CHEMICAL STUDY OF THE STRUCTURE
963
parameters of various N-substituted p-quinonimines
from the experimental data obtained by X-ray analysis.
As a result, we could be able to compare the reactivity
of these compounds and the position of reactive
centers in their molecules.
0.032 (MNDO), 0.029 (AM1), 0.021 Å (PM3); bond
angles: 6.365 (MINDO/3), 2.639 (MNDO), 4.755
(AM1), 2.608 deg (PM3).
We previously showed that the site of addition of
chlorine or bromine atom in reactions of quinonimines
with hydrogen halides may be interpreted on the basis
of PM3 calculations [10]. In the present work we
continued studies in this line. Adams and Looker [12]
were the first to report on the reaction of N-arylsul-
fonyl-1,4-benzoquinonimines with hydrogen chloride
[11]; the authors formulated a rule which allowed
prediction of the site of chlorine entry into the quinoid
ring. According to this rule, protonation of the most
basic center in the molecule occurs in the first step
[12], and the subsequent attack by chloride ion on
position 2 of the quinoid ring is followed by proto-
tropic rearrangement. However, the rule does not work
with N,N'-disubstituted 1,4-benzoquinonediimines in
which different substituents have similar electron-
acceptor or electron-donor properties.
Our previous studies have shown that the reactivity
of quinonimines is strongly influenced by the bond
angle at the imino nitrogen atom (C=N–X) [2]. We
examined the dependence of the potential energy (E)
of molecules I–X and their enthalpies of formation
(∆Hf) on the CNX angle. The X-ray diffraction data for
compounds I [3], II [4], III, X [5], IV [6], V [2], VI
[7], VIII [8], and IX [9] have already been reported.
The calculations were performed by optimizing the
other geometric parameters at a fixed CNX angle
which was varied in the range from 100 to 180°
through a step of 10°. Analysis of the results showed
that the PM3 and MNDO methods give the most
pronounced minima of E and ∆Hf at CNX angles
similar to those found by X-ray analysis.
In order to elucidate in more detail the applicability
of the above quantum-chemical methods for practical
purposes we performed complete geometry optimiza-
tion of molecules I–X. The least deviations of the
calculated bond lengths and bond angles from the
corresponding experimental parameters were obtained
with the use of the PM3 procedure. The average devia-
tions are as follows: bond lengths: 0.039 (MINDO/3),
Taking into account that hydrobromination and
hydrochlorination of N-p-tolyl-1,4-benzoquinonimine
results in chlorine addition at position 3, Burmistrov
and co-workers [13–15] proposed a universal proce-
dure for determination of the direction of hydrohalo-
genation on the basis of redox potentials. The proce-
dure implied analysis of the thermodynamic stability
of intermediate products having an ortho-quinoid
Scheme 1.
Me
Me
PhSO2N
O
+
HCl
PhSO2NH
OH
Cl
XI
XII
R
R
Cl
+
HCl
O
S
O
S
O
O
N
O
HN
OH
XIIIa, XIIIb
XIVa, XIVb
Me
Cl
Me
Cl
PhSO2N
O
+
HCl
PhSO2NH
OH
Cl
XVI
XV
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 7 2004

AVDEENKO et al.
964
Scheme 2.
Charges
Single-electron densities (LUMO)
Me
Me
–0.1871
0.1054
XI
N
O
N
O
PhSO2
PhSO2
–0.1293 –0.1339
0.1293 0.1339
O
O
XIIIa
–0.1349
0.1874
S
S
O
O
N
N
O
N
O
O
–0.0621 –0.1683
0.0615 0.0619
Me
Me
–0.1438
0.0889
PhSO2
PhSO2
XVa
O
O
N
N
–0.0877
0.1092
Cl
Cl
Me
Me
–0.0907
0.0864
XVb
N
O
PhSO2
PhSO2
–0.1405
0.1121
Cl
Cl
structure. However, experimental measurement of
redox potentials of quinonimines is very difficult and
laborious or even impossible. Furthermore, this redox
procedure cannot be applied to some quinonimines
because of specific structure of the quinoid ring.
charges and single-electron densities in molecules XI,
XIIIa, XV, calculated by the PM3 method. The cal-
culations were performed for both possible isomers
of XV. It is seen that distribution of single-electron
densities on carbon atoms in the quinoid ring is very
consistent with the site of halogen addition observed
experimentally (indicated by arrows). Chloride or
bromide ion attacks that carbon atom of the quinoid
ring, which possesses the highest single-electron
density in the lowest unoccupied molecular orbital
(LUMO). The LUMO energies of compounds XI,
XIIIa, XVa, and XVb, calculated by the PM3 method,
are –1.747, –2.241, –1.898, and –1.886, respectively;
the HOMO energies of halide ions are –3.479 (Cl–) and
–3.598 (Br⎯).
We tried to solve the problem with the use of
quantum-chemical calculations; in other words, we
now propose an alternative procedure for prediction of
the direction of hydrohalogenation of p-quinonimines.
Our procedure properly describes the addition of HCl
and HBr to various quinonimines having various sub-
stituents both at the nitrogen atom and in the quinoid
ring. This method extends the potential of prediction
of the site of halogen addition in hydrohalogenation
and does not contradict the procedure based on redox
potentials.
EXPERIMENTAL
We were the first to effect hydrochlorination of
compounds XI, XIIIa, XIIIb, and XV, which afforded
addition products XII, XIVa, XIVb, and XVI, respec-
tively (Scheme 1). The site of chlorine addition in
these reactions cannot be predicted on the basis of
redox potentials. Scheme 2 shows distribution of
Quantum-chemical calculations were performed on
an AMD-K-6 PC using MOPAC 6 software package.
The 1H NMR spectra were recorded on a Varian VXR-
300 spectrometer (300 MHz) from solutions in CDCl3;
the chemical shifts were measured relative to TMS.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 7 2004

QUANTUM-CHEMICAL STUDY OF THE STRUCTURE
965
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 7 2004