Interpretation of retention indices in gas chromatography for establishing structures of isomeric products of alkylarenes radical chlorination

Article abstract of DOI:10.1023/A:1012343416008

By an example of previously uncharacterized products obtained by alkylarenes radical chlorination was demonstrated that combination of various interpretation methods applied to the retention indices (RI) in the gas chromatography on the standard nonpolar phases (comparison of RI of products and initial compounds, characteristics of succession of the chromatographic elution of the structural isomers with the use of estimation of molecular dynamic parameters, application of the additive schemes to RI calculation, and using of structural analogy CH₃?Cl for testing the results obtained) permitted unambiguous identification of the structure even without data of mass spectrometry.

Full text of DOI:10.1023/A:1012343416008

Russian Journal of Organic Chemistry, Vol. 37, No. 2, 2010, pp. 270 280. Translated from Zhurnal Organicheskoi Khimii, Vol. 37, No. 2, 2001,
pp. 283 293.
Original Russian Text Copyright
2001 by Zenkevich.
Interpretation of Retention Indices in Gas Chromatography
for Establishing Structures of Isomeric Products
of Alkylarenes Radical Chlorination*
I. G. Zenkevich
St. Petersburg State University, St. Petersburg, 198904 Russia
Received March 1, 2000
Abstract By an example of previously uncharacterized products obtained by alkylarenes radical chlorination
was demonstrated that combination of various interpretation methods applied to the retention indices (RI) in
the gas chromatography on the standard nonpolar phases (comparison of RI of products and initial
compounds, characteristics of succession of the chromatographic elution of the structural isomers with the
use of estimation of molecular dynamic parameters, application of the additive schemes to RI calculation,
and using of structural analogy CH3
Cl for testing the results obtained) permitted unambiguous
identification of the structure even without data of mass spectrometry.
Among the problems of identification of
components in mixtures of organic compounds with
the use of GC-MS method one of the most difficult
cases is structure determination of isomers
characterized with insignificant distinctions in the
mass spectra (isomeric hydrocarbons in oil, ecotoxic
compounds of various classes, in particular, posi-
tional isomers of polychlorinated aromatic com-
pounds etc.). The attempts of identification of such
objects usually lead to uncertain results and numerous
errors. A typical case of this formal approach consists
in sometimes occurring description of several
different components with the same structure [1]. The
risk provided by this uncritical treatment of a long
series of identified compounds was indicated already
in [2]. In all these cases the reliable identification is
possible only with taking into account retention
indices of gas chromatography (in formulas RI) and
the appropriate database. However as was already
several times mentioned the volume of the modern
databases on chromatography is considerably smaller
than that for mass spectrometry. This drawback sig-
nificantly hampers the practical application of these
analytical parameters. Besides when the investigation
objects are isomeric components of first obtained
reaction mixtures that have not been characterized
before either by mass spectra or RI, then the tradi-
tional approaches to identification consisting in
revealing formal coincidence of analytical parameters
are fully unacceptable. In such cases just the
chromatographic constants become important since
unlike the mass spectra they may be fairly accurately
predicted even for previously unstudied compounds
classes with the use of additive calculation schemes,
principles of structural similarity, calculations based
on physicochemical characteristics etc. An example
of a new approach to interpretation of RI for the
reaction products of ethoxycarbonylcarbene with
various substrates with the use of molecular dynamics
was demonstrated in [3].
The necessity of application of the chromato-
graphic parameters arises also in characterizing
relatively simple classes of organic compounds. For
instance, up till now are virtually lacking the
analytical data on the products of alkylarenes radical
chlorination, although the reactions of this class are
extensively studied [4]. The identification problems
with chlorinated derivatives of various series are
hampered by low structural specificity of their mass
spectra that do not permit to locate the position of the
halogen atom in the molecule. The most significant
characteristic of mass spectra is useful only for group
identification: In the molecular ions of compounds
containing structural fragments C(sp3) Cl the
prevailing fragmentation consists in elimination of
Cl. radical, whereas p- conjugation in the
fragments C(sp2) Cl causes predominant formation
of [M R]+ ions (R are hydrocarbon radicals) with
conservation of chlorine atom [5]. Therefore the
spectra of ion series of alkylchloroarenes and (chloro-
alkyl)arenes should be considerably different; how-
*
The study was carried out under financial support of the Rus-
sian Foundation for Basic Research (grant no. 97-03-33116).
1070-4280/01/3702-0270$25.00 2001 MAIK Nauka/Interperiodica

INTERPRETATION OF RETENTION INDICES IN GAS CHROMATOGRAPHY
271
ever they are lacking in a fairly comprehensive
compilation given in [6], and it proves that these
compounds are poorly investigated even by mass
spectrometry.
with the use of the simplest models to predict the
succession of elution of the isomeric chloroderiv-
atives.
The establishing of the structures of the reaction
mixtures components is considerably simplified by
the fact that simultaneously arise all possible products
of the radical chlorination by replacement of non-
equivalent hydrogen atoms in the alkyl fragments of
molecules. At sufficiently high efficiency of capillary
columns it is possible to register the peaks of all these
components. In theory it is possible to estimate their
relative intensity proportional to nH krel, where nH
is a number of equivalent hydrogen atoms in the
molecule, krel are the relative rate constants of the
radical chlorination (for instance, with alkanes in
CCl4 ksec/kprim amounts to 1.81 0.03, and ktert/kprim
to 3.0 0.1 [4]). However such estimates may be used
only as provisional since the relative quantities of
isomers are changed by secondary processes (de-
hydrochlorination and formation of polychlorinated
derivatives), and the lability of hydrogen atoms in
benzyl position of the molecules may be notably
unlike that in alkanes.
RI from gas chromatographic data of some
simplest (chloroalkyl)arenes are listed in the hand-
book [7]. These retention indices are not inter-
laboratory invariants and cannot serve for identifica-
tion [8]. The RI of products obtained by radical
chlorination of p-xylene [9] were measured on non-
standard phases and therefore cannot be compared
with the modern data for nonpolar polydimethyl-
siloxane phases. The above reasons were prerequisite
for developing two calculation methods for RI of such
chloroderivatives: a) proceeding from structural
analogy CH3 Cl and basing on the RI of the cor-
responding hydrocarbons with the use of statistically
processed values of increments Cl CH3 [ 61 15 at
C(sp2) and 128 13 index units at C(sp3)] [10], and
b) from the boiling points of the structural analogs
along the equation logRI(X Cl) = alogbp(X CH3) +
bA+ c [11].
Thus the solution of an important practical
problem of identification of isomeric products
obtained by radical chlorination of substituted
aromatic hydrocarbons due to low informative quality
of their mass spectra requires first of all an interpreta-
tion of their chromatographic parameters in the
absence of the necessary reference source. The mass-
spectrometrical information in this case is replaced by
a priori knowledge on the nature of the compounds
under investigation (we know the class of the sub-
stances) that can be supplemented with characteristics
of the influence of the variations in the chlorination
conditions on the composition of the reaction mix-
tures etc. This study contains both experimental
measurement of RI of insufficiently characterized
(chloroalkyl)arenes, and in extension of the investiga-
tion carried out in [3, 12] further development of
technique for structure determination of isomer
products formed in organic reactions with the use of
these data.
Among the known processes of radical chlorina-
tion of alkylarenes no one excludes the parallel ionic
chlorination in the aromatic ring. The fraction of
these products is higher for the heterophase process
B
(see Experimental), and it decreases with
growing overall number of carbon atoms in the alkyl
substituents. The comparison of the set of chlorina-
tion products produced by various procedures turned
out to be a very important source of additional in-
formation on their chemical nature. It was used for
differentiation of the chlorinated substances according
to the substitution type.
A preliminary information on the nature of
chlorination products obtained from alkylarenes may
be gained from comparison of the difference between
RI of the products and the initial hydrocarbons
(criterion I). The values RI corresponding to trans-
formation H Cl differ depending on the degree of
substitution of the reaction site and on its hybridiza-
tion state, namely 189 19 (ArH ArCl), 228 14
The solution of the problem under consideration
cannot consist in application of a single universal
interpretation method of chromatographic data; only
(H
Cl ) [13]. From these estimates follows that with
degree of confidence = 0.95 the value of RI at
Cl ), 182 22 (H
Cl ) and 175 10 (H
combination of various procedures provides
a
possibility to get an unambiguous answer. This
combination should include several versions of IR
estimation by additive schemes, the calculation of
intramolecular vibrational and rotational energies by
molecular dynamics method, and, separately, evalua-
tion only vibrational component of these energies
replacement of the primary hydrogen should be no
less than 200 and no more than 256. The larger RI
values correspond only to polychlorinated com-
pounds. On the other hand, the value RI<138 ( =
0.95) are excluded for any monochlorinated deriv-
atives, and therefore the criterion RI<105 permits
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 2 2001

272
ZENKEVICH
unambiguous identification in the reaction mixtures of
the principal side products resulting from dehydro-
chlorination of chloroalkylarenes, conjugated alkenyl-
benzenes. The above estimates of RI also show that
the ranges of these parameters for the sec- and tert-
chloroalkyl derivatives should overlap.
energy. If the consideration is limited to ordinary
bonds C C and C X (where X are heteroatoms or
structural fragments including cycles and multiple
bonds; equal number of C H bonds in isomers is not
taken into account), and each ordinary bond is
regarded as a harmonic oscillator, then the overall
vibrational energy of molecules should be propor-
tional to the value U = k[M/(mi mj)]0.5, where M is
molecular weight, mi+ mj = M is the weight of the
structural fragments of molecules attached to each
bond under consideration. The values of factors k for
ordinary bonds may be taken as unity without further
differentiation. It was shown by examples of isomeric
alkanes, dialkyl sulfides, and alkylamines that E and
U values are in good correlation; therefore the estima-
tion of RI in gas chromatography may be performed
with the use of an equation of RI = aU+ b (a<0)
type [14]. Thus alongside computer simulation by
molecular dynamics method it is possible to use
simplest estimation of intramolecular vibrational
energy U that may be computed even on a micro-
calculator (criterion III).
If is fulfilled the above stated the most important
condition of the structural interpretation of chromato-
graphic data, registration of the signals of every
possible product of radical chlorination, then the
unambiguous determination of isomers structure is
equivalent to prediction of the succession of their elu-
tion from the chromatography column (ranged RI).
The analogous feature of the reaction mixtures
composition provided a possibility, for instance, to
establish the structures of regio- and stereoisomers in
the products of Diels Alder reaction [12] from the
estimates of their intramolecular vibrational and
rotational energies obtained by computer simulation
using the molecular dynamics method. The essence
of this approach is based on the fact that for processes
resulting in mixtures of isomer compounds of the
type A+B C1+ C 2+ . . . + C n the differences
between RI of products and initial reagents RI(i) =
RI(i) RI(A) RI(B) are in fair correlation with the
corresponding differences of the overall vibrational
and rotational energies of the products and reagents
E(i) = E(i) E(A) E(B). The observed oppositely
directed changes in parameters RI and E can be
approximated in quite a few cases by linear equations
RI = a E+ b (a<0). The coefficients of such
relations are calculated from the RI and E values
for the known substances; thereafter these relations
can be applied for confirming or rejecting the
assumed structures of the other products [3]. How-
ever this mathematical approach is not the only
possible way of using the results of calculations by
molecular dynamics method for interpretation of the
chromatography data. It is presumable that for
practical problems more favorable is a simpler rule
(criterion II): isomeric products of organic reactions
formed for the same precursors are eluted from the
chromatograph column in the order of decrease in
their dynamic molecular parameters E. Just this
algorithm of data interpretation was applied to
structural assignment of the isomeric adducts arising
in [2+4]-cycloaddition [12].
This statement was up till now considered in a
single study [15], and thus it required additional
testing by example of compounds chemically
related to the chloroalkylarenes in question. In
Table 1 are compared the differences of RI for
some chlorine-containing substances (polychloro-
compounds included) referred to RI of the isomers
with maximal RI on the standard nonpolar phases,
and the corresponding differences in U parameters.
All the presented data unambiguously show that the
succession of chromatographic elution always cor-
responds to the decrease in U values, similarly to the
decrease in the E parameters. Moreover, the RI and
U values for all the chlorine-containing compounds
listed in Table 1 fit to unique correlation equation
RI = (963 129) U+(11 11); r = 0.942; s =
15.9. A similar approach may be extended also to the
group of chloroalkylarenes under consideration.
However that would be possible only after reliable
identification of some compounds belonging to this
class. Therefore not to hamper the logical scheme of
data interpretation we used here only the criterion of
opposite direction in changes of chromatographic RI
and absolute values of U parameter. Some distinc-
tions in structure of molecules (e.g. positional
isomerism) do not appear in variations of this simple
U criterion preventing its application.
If the main cause of difference in the chromato-
graphy parameters of isomers with similar energy of
dispersion interaction sorbate stationary phase is
the dissimilar molecular dynamic parameters, then
simpler models can be suggested taking into account
only vibrational components of the intramolecular
The combination of the mentioned three criteria
for the structural interpretation of the chromato-
graphic parameters already is sufficient for assigning
structures to most of we registered products of alkyl-
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INTERPRETATION OF RETENTION INDICES IN GAS CHROMATOGRAPHY
273
Table 1. The dependence of differences in retention indices ( RI) of some simple chlorine-containing compounds
on variation in U parameter
Isomeric chlorine-containing
compounds
RI
U
RIb
Ub
1,2-Dichloroethane
1,1-Dichloroethane
1-Chloropropane
2-Chloropropane
632
568
531
9
7
5
5
0.624
0.702
0.749
0.802
0.493
0.470
0.930
0.988
1.004
1.031
0.789
0.876
0.901
0.963
64
35
7
0.078
0.053
0.023
496
1-Bromo-2-chloromethylbenzene
1-Bromomethyl-2-chlorobenzene
1-Chlorobutane
2-Methyl-1-chloropropane
2-Chlorobutane
2-Methyl-2-chloropropane
1,3-Dichloropropane
1,2-Dichloropropane
1,1-Dichloropropane
2,2-Dichloropropane
1244a
1237a
637
5
4
3
4
604
601
540
760 12
688 11
668a
33
36
93
0.058
0.074
0.101
72
92
155
0.087
0.112
0.179
605
7
a
No published experimental data; the RI presented are estimated along additive schemes.
The differences RI and U are given referred to the isomers with maximal retention parameters.
b
arenes chlorination. However as additional in-
dependent test it is useful to apply also an additive
scheme including increments of structural transforma-
tions Cl CH3 at sp3- and sp2-hybridized carbon
additive scheme should be mentioned which does not
require preliminary calculation of increments for any
structural transformations of molecules. This most
traditional element of the majority of additive
schemes known in chemistry may be replaced by
direct use of informational databases and necessary
operations with structural formulas of organic
compounds selected by the maximum structural
similarity with the characterized object. Up till now
this approach was used in calculation of RI for
metabolites of polychlorobiphenyls, monohydroxy-
polychlorobiphenyls (849 congeners, the calculation
in any other way virtually impossible) [14], and for
nitroanilines in the reversed-phase high resolution
liquid chromatography [16]. The specific features of
this criterion V can be illustrated by an example of
RI estimation for two isomers obtained by chlorina-
tion of isopropylbenzene.
atoms ( 128 13 and
respectively) [10].
61 15 index units,
The latter procedure provides a possibility to
compare RI of various chlorinated products with the
data for isostructural alkyl-substituted arenes with one
carbon atom more in the molecule (criterion IV).
Here we use this criterion at the final stage of the
data interpretation in order to check the validity of
structural assignments; presumably further applica-
tions of this criterion will provide it with more
importance.
In conclusion of enumeration of interpretation
methods for RI that are used in combination one more
C6H5CH2CH2Cl + C6H5CH(CH3)2 C6H5CH2CH3
1090 1 914 6 854 9
(experimental value 1152 1)
C6H5CH(CH3)2 + (CH3)3C Cl CH(CH3)3
C6H5CH(CH3)CH2Cl
1150 11
+
=
C6H5C(CH3)2Cl
1078 9
914 6
+
540 6
376 2 =
(experimental value 1070 1)
In the latter case this criterion is more important
than the auxiliary condition IV that results in unsatis-
factory agreement of RI for (1,1-dimethylethyl)-
benzene with the published data (Table 2). Using
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 2 2001

274
ZENKEVICH
analogous reasoning it is possible to determine, e.g.,
the order of elution of isomeric dimethyl-bis-(chloro-
methyl)benzenes arising in chlorination of 1,2,4,5-
tetramethylbenzenes. Another advantage of this
criterion compared to the condition IV is the use for
estimating RI of the data on simple compounds that
are usually more accurately characterized than higher
homologs.
benzenes and to the products chlorinated into the
aromatic ring. The auxiliary character of this
parameter is due to the fact that the relative elution
order of isomeric alkylchlorobenzenes and their
structural analogs, alkylmethylbenzenes is usually
dissimilar, and thus the average accuracy of this
criterion should not exceed the standard deviations in
the RI(Cl CH3) values proper. Nonetheless, the
mean deviations of the estimated RI of hydrocarbons
from the known reference data amount only to 14 10
and 8 6 index units for chloroalkyl- and alkylchloro-
benzenes respectively. To our regret, starting from
the chlorination products of pentylbenzene isomers
this criterion becomes less efficient due to lack of
reference data for the majority of hexylbenzene
isomers and for more complicated alkylarenes (no
data in the last column of Table 2).
The combination of all the mentioned modes of
RI interpretation was used for establishing structures
of chlorination products obtained from 20 alkyl-
substituted benzenes listed in Table 2 (in the table
was additionally included
a
representative of
another group of compounds, acenaphthene, whose
chlorinated derivatives also were not yet char-
acterized). In all cases the variation of reaction
conditions (increased excess of chlorine, repeated
chlorination of the reaction mixtures) permits
registering of various di- and trichloroderivatives; in
order to reduce the length of the table this complete
information was given only for six hydrocarbons
among those presented in the table. However the
concepts used in interpretation of the chromato-
graphic parameters of polychlorinated derivatives are
the same as the rules recommended and applied to
monochlorinated compounds. Only in four cases (for
alkylarenes containing alkyls with five or more
carbon atoms) we did not find any products of
alternative ionic chlorination in the aromatic ring. In
six reaction mixtures (mostly with tert-chloroalkyl-
arenes) was observed formation of dehydrochlorina-
tion products, 1-alkenylarenes. For each chlorination
product in Table 2 is mentioned the procedure of
chlorination (A and/or B) that yields this substance in
amounts comparable with the other isomers (no less
than 0.5 1% from the sum of peak areas of all
chlorinated products), are listed the main parameters,
and the data applied to isomer structure determina-
tion. In brackets are indicated the known now refer-
ence data on the RI of the respective products (only
for 18 among 118 compounds). Here are also given in
decreasing order the values of the dynamic molecular
parameters E and U used in predicting the succession
of isomers elution. In all cases but two the decreasing
orders for both these values are in agreement. The
exceptions are 1,2-dimethyl-4-(1,1-dimethylethyl)-
benzene (at close values of U is more significant the
difference in E) and 1,4-dimethyl-2-butylbenzene
(here on the contrary is more significant the differ-
ence in U, and at equal U values was considered the
decreasing order of E). And, finally, the last column
of the table includes the results of application of
RI(Cl CH3) criterion both to (chloroalkyl)
Thus just the combination of various methods of
interpretation applied to retention indices in gas
chromatography gave a possibility to establish struc-
tures of over hundred chlorinated aromatic hydro-
carbons directly in the reaction mixtures avoiding the
preparative isolation of the substances. Now these
first obtained new data on RI may be entered into the
chromatographic databases and thereafter used for
identification along traditional
methods by
comparison of the measured and reference analytical
parameters. Similar combinations of interpretation
procedures for the chromatographic parameters may
be extended to the other groups of isomeric organic
compounds with a priori known chemical nature.
EXPERIMENTAL
Gas-chromatographic analysis of the product
mixtures obtained by alkylarenes chlorination was
carried out on chromatograph Biokhrom-1 equipped
with a flame-ionization detector and quartz capillary
column 25 m 0.2 mm (4300 theoretical plates per
1 m), stationary phase OV-101, temperature pro-
1
grammed from 60 to 240 C at a rate 4 deg min
carrier gas nitrogen, pressure at input 0.8 atm, split
ratio 1: 30, samples 0.6 0.8 l. The determination of
linear-logarithmic retention indices was performed
with the use of a mixture of reference n-alkanes
C6 C18; the retention times were registered by an
integrator TR 2213. The indices were calculated
according to software published in the supplement to
textbook [17].
The calculation of intramolecular vibrational and
rotational energies by molecular dynamics methods
were carried out by the use of HyperChem 3 software
with the same parameters as in [3]: temperature of
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 2 2001

Table 2. Results of structural interpretation of retention indices in gas chromatography for chlorination products obtained from alkylaromatic
hydrocarbons C7 C12
Initial alkylarene
RIb
RI of reaction
products
IRc
Structure assignedd
Parameters for structure
assignemente
Criterion
I
(na)
(synthesis method)
(Cl CH3)
Toluene (1)
Ethylbenzene (2)
760 9 986 7
854 9 1028 1 (B)
226
174
Benzyl chloride
1-Chloro-4-ethylbenzene
(1-Chloroethyl)benzene
IU > 200
[1031 7]
[1043 7], U 0.638
858 (854)
967 (951)
916 (914)
1044 1 (A, B) 190
1090 1 (A)
885 9 1046 1 (B)
236
161
(2-Chloroethyl)benzene
[1076 14], (70.542, IU > 200 962 (945)
o-Xylene (1)
1,2-Dimethyl-3-chlorobenzene
1,2-Dimethyl-4-chlorobenzene
1-Methyl-2-chloromethylbenzene
[1060 9]
985 (1011)
1012 (984)
970 (967)
1073 1 (A, B) 188
1098 2 (A)
[1071 10]
213
[1088 14], IU > 200
Polychloro derivatives
f
1248 1 (B)
1296 1 (A)
1434 2 (B)
1-Methyl-4-chloro-2-chloromethylbenzene
2 206 1,2-Bis(chloromethyl)benzene
1059 (1067)
1040 (1040)
1117 (1149)
993 (984)
f
1-Chloro-3,4-bis(chloromethyl)benzene
1,3-Dimethyl-4-chlorobenzene
1-Methyl-3-chloromethylbenzene
m-Xylene (1)
865 8 1054 2 (A, B) 189
[1045 8]
IU > 200
1098 1 (A)
233
970 (950)
Polychloro derivatives
1230 1 (B)
1238 1 (B)
863 8 1044 2 (A, B) 181
1-Methyl-2-chloro-5-chloromethylbenzene E 41.5
1-Methyl-4-chloro-3-chloromethylbenzene E 41.2
1041 (1074)
1049 (1064)
983 (984)
p-Xylene (1)
1,4-Dimethyl-2-chlorobenzene
1-Methyl-4-chloromethylbenzene
Polychloro derivatives
[1045 17]
IU > 200
1098 2 (A)
235
970 (951)
f
1213 1 (B)
1437 1 (B)
945 9 1111 1 (B)
1-Methyl-2-chloro-4-chloromethylbenzene
2-Chloro-1,4-bis(chloromethyl)benzene
1-Propyl-4-chlorobenzene
(1-Chloropropyl)benzene
(2-Chloropropyl)benzene
1024 (1074)
1120 (1145)
[1132 6]
E 47.3, U 0.831
E 46.7, U 0.789
E 46.5, U 0.690, IU > 200 1036 (1046)
Propylbenzene (3)
166
1050 (1042)
1005 (1003)
1010 (997)
1133 1 (A, B) 188
1138 1 (A, B) 193
1164 1 (A, B) 219
(3-Chloropropyl)benzene
Isopropylbenzene (2) 914 6 965 1 (A, B)
51
(1-Methylethenyl)benzene
[966 6]
1070 1 (A)
1080 1 (B)
1102 1 (B)
1152 1 (A)
156
166
188
238
(1-Methyl-1-chloroethyl)benzene
1-(1-Methylethyl)-4-chlorobenzene
1-(1-Methylethyl)-2-chlorobenzene
(1-Methyl-2-chloroethyl)benzene
E 50.4, U 0.893,g
[1101]
942 (984)
1019 (1013)
1041 (1024)
[1097 20]
E 47.9, U 0.643, IU > 200,g 1024 (1003)

Table 2. (Contd.)
Initial alkylarene
RIb
RI of reaction
products
Structure assignedd
Parameters for structure
assignemente
Criterion
I
(na)
IRc
(synthesis method)
(Cl CH3)
f
f
1,2,4-Trimethyl- 984 10 1177 1 (A, B) 193
benzene (3) 1182 2 (A, B) 198
1,2,4-Trimethyl-5-chlorobenzene
1,2,4-Trimethyl-3-chlorobenzene
1,2-Dimethyl-4-chloromethylbenzene
1,3-Dimethyl-4-chloromethylbenzene
1,4-Dimethyl-2-chloromethylbenzene
1116 (1003)
1121 (1137)
1072 (1074)
1080 (1067)
1100 (1064)
1200 1 (A)
1208 1 (A)
1228 1 (A)
216
224
244
E 49.0, IU > 200
E 48.2, IU > 200
E 47.8, IU > 200
Polychloro derivatives
1364 1 (B)
1368 2 (A, B)
1392 2 (A, B)
1399 1 (A)
1411 1 (A)
1533 1 (A)
1574 1 (B)
1599 1 (A)
Dimethylchloro(chloromethyl)benzene
Dimethylchloro(chloromethyl)benzene
1-Methyl-2,5-bis(chloromethyl)benzene
Structure was not found
Structure was not found
E 49.1
E 49.1
E 48.2
1175
1179
1136 (1145)
1152 (1149)
1155 (1149)
1283
2 204 1-Methyl-2,4-bis(chloromethyl)benzene
2 208 1-Methyl-3,4-bis(chloromethyl)benzene
2 214 Dichloro(chloromethyl)benzene
Chlorobis(chloromethyl)benzene
Structure was not found
Structure was not found
1257
1215 (1227)
3 205 1,2,4-Tris(chloromethyl)benzene
1,3,5-Trimethyl- 963 13 1152 1 (A, B) 189
1,3,5-Trimethyl-2-chlorobenzene
1,3-Dimethyl-5-chloromethylbenzene
1092 (1107)
IU > 200
benzene (1)
1196 1 (A)
233
1068 (1045)
Polychloro derivatives
1344 2 (A, B)
1348 1 (A)
1402 1 (A)
1525 1 (B)
1566 1 (A)
1596 2 (A)
1,3-Dimethyl-2-chloro-5-chloromethylbenzene
1,3-Dimethyl-4-chloro-5-(chloromethyl)benzene
E 49.5
E 43.3
1155 (1194)
1159 (1184)
1146 (1129)
1275
2 220 1-Methyl-3,5-bis(chloromethyl)benzene
1,3-Dimhyl-2,3-dichloro-5-(chloromethyl)benzene
1-Methyl-2-chloro-3,5-bis(chloromethyl)benzene
3 211 1,3,5-Tris(chloromethyl)benzene
(Z)-1-Butenylbenzene
f
f
1249
1212 (1203)
1050 (1138)
1100 (1081)
1104 (1105)
1112 (1112)
1128 (1143)
1128 (1143)
f
Butylbenzene (4) 1046 5 1111 1 (A, B) 65
1213 1 (B)
167
1-Butyl-4-chlorobenzene
(1-Chlorobutyl)benzene
(2-Chlorobutyl)benzene
(3-Chlorobutyl)benzene
(4-Chlorobutyl)benzene
1-Methyl-4-(1-methylethenyl)benzene
Mixture:
1-Methyl-4-(1-methylethyl)-3-chlorobenzene (I)
1-Methyl-4-(1-methylethyl)-2-chlorobenzene (II)
1-Methyl-4-(1-methyl-1-chloroethyl)benzene
1-(1-Methylethyl)-4-chloromethylbenzene
1-Methyl-4-(1-methyl-3-chloroethyl)benzene
E 53.7,
E 53.7,
E 53.4,
E 53.1,
E 53.1,
[1073 8]
[1188] (I)l [1190] (II)
I (1124)
II (1128)
U 0.996
U 0.974
U 0.930
U 0.829
U 0.829
1228 1 (A, B) 182
1232 2 (A, B) 186
1240 1 (A, B) 194
1256 2 (A)
210
p-Cymene (3)
1013 5 1076 1 (A, B) 63
1189 1 (B)
176
1128
1199 1 (A, B) 186
1252 2 (A, B) 239
1258 2 (A, B) 245
E 55.7, U 1.156
E 54.3, U 1.078, IU > 200 1124 (1107)
E 54.3, U 1.056, IU > 200 1130 (1101)
1071 (1078)

Table 2. (Contd.)
Initial alkylarene
RIb
RI of reaction
products
Structure assignedd
Parameters for structure Criterion
(na)
IRc
assignemente
I
(synthesis method)
(Cl CH3)
1,2,4,5-Tetramethyl- 1103 4 1267 1 (A, B) 164
1,2,4,5-Tetramethyl-3-chlorobenzene
1,2,4-Trimethyl-5-chloromethylbenzene
[1262 5]
IU > 200
1206 (1259)
1191 (1173)
benzene (1)
1319 1 (A, B) 216
Polychloro derivatives
1497 1 (B)
1530 1 (B)
1561 1 (B)
Trimethylchloro(chloromethyl)benzene
2 214 1,2-Dimethyl-4,5-bis(chloromethyl)benzene
2 229 Mixture:
Structure was not found
g
1274 (1264)
1305 (-)
g
1,3-Dimethyl-4,6-bis(chloromethyl)benzene
1,4-Dimethyl-2,5-bis(chloromethyl)benzene
Pentylbenzene (5)
1143 9 1322 2 (A, B) 179
1328 1 (A, B) 185
1334 1 (A, B) 191
1342 1 (A, B) 199
1353 1 (A, B) 210
(1-Chloropentyl)benzene
(2-Chloropentyl)benzene
(3-Chloropentyl)benzene
(4-Chloropentyl)benzene
(5-Chloropentyl)benzene
U 1.145
U 1.133
U 1.108
U 1.062
1194 (1169)
1200 (1191)
1206 (-)
1214 (1187)
1225 (1240)
U 0.959, IU > 200
2-Phenylpentane (5) 1081 10 1184 3 (A, B) 103
(2 diastereomer pairs) 1245 1 (A) 164
(E)-(1-Methyl-1-butenyl)benzene
1-(1-Methylbutyl)-4-chlorobenzene
(1-Methyl-1-chlorobutyl)benzene
(1-Methyl-2-chlorobutyl)benzeneh
(1-Methyl-3-chlorobutyl)benzeneh
(1-Chloromethylbutyl)benzene
(1-Methyl-4-chlorobutyl)benzene
f
1117 (-)
1126 (-)
1151 (-)
1158 (-)
1180 (-)
1190 (-)
1254 1 (A, B) 173
1279 2 (A, B) 198
1286 2 (A, B) 205
1308 4 (A, B) 227
1318 4 (A, B) 237
U 1.254
U 1.236
U 1.200
U 1.152, IU > 200
U 1.081, IU > 200
3-Phenylpentane (3) 1076 12 1155 2 (A, B) 79
(E)-(1-Ethyl-1-propenyl)benzene
(Z)-(1-Ethyl-1-propenyl)benzene
(1-Ethyl-1-chloropropyl)benzene
(1-Ethyl-2-chloropropyl)benzeneh
(1-Ethyl-2-chloropropyl)benzeneh
(1-Ethyl-3-chloropropyl)benzene
(1 diastereomer pair)
1171 1 (A, B) 95
1259 1 (A, B) 183
1276 2 (A, B) 200
1282 2 (A, B) 206
1310 2 (A, B) 234
E 64.6
E 62.7
E 62.7
E 59.9, IU > 200
1131 (-)
1148 (-)
1154 (-)
1182 (-)
3-Methylbutylbenzene 1112 7 1279 2 (A, B) 167
(3-Methyl-1-chlorobutyl)benzene
(3-Methylbutyl)-4-chlorobenzene
(3-Methyl-2-chlorobutyl)benzene
(3-Methyl-3-chlorobutyl)benzene
(3-Methyl-4-chlorobutyl)benzene
U 1.212
1151 (-)
1242 (-)
1186 (-)
1198 (-)
1214 (-)
f
(4)
1303 1 (A, B) 191
1314 2 (A, B) 202
1326 3 (A, B) 214
1342 2 (A, B) 230
(1 diastereomer pair)
U 1.200
U 1.175
U 1.073, IU > 200

Table 2. (Contd.)
Initial alkylarene
RIb
RI of reaction
products
IRc
Structure assignedd
Parameters for structure Criterion
(na)
assignemente
I
(synthesis method)
(Cl CH3)
1-Methyl-4-(1,1-di- 1078 4 1260 1 (B)
182 1-Methyl-4-(1,1-dimethylethyl)-3-chlorobenzene
184 1-Methyl-4-(1,1-dimethylethyl)-2-chlorobenzene
1199 (1168)
1201 (1191)
1198 (1169)
1225 (1184)
methylethyl)benzene
(2)
1262 1 (B)
1326 2 (A, B) 248 1-(1,1-Dimethylethyl)-4-chloromethylbenzene E 64.8, IU > 200
1353 1 (A, B) 275 1-Methyl-4-(1-methyl-1-chloromethylethyl)-
E 64.3, IU > 200
benzene
3-Methyl-2-phenyl-
butane (4) (1 dia-
stereomer pair)
1068 2 1262 2 (A, B) 194 (1,2-Dimethyl-1-chloropropyl)benzene
1279 2 (A, B) 211 (1,2-Dimethyl-2-chloropropyl)benzene
E 66.5
E 64.8
E 63.2, IU > 200
E 63.2, IU > 200
1134 (-)
1151 (-)
1168 (-)
1183 (-)
1296 1 (B)
1311 2 (B)
231 (1,2-Dimethyl-3-chloropropyl)benzeneh
243 (1,2-Dimethyl-3-chloropropyl)benzeneh
1,2-Dimethyl-4-(1,1- 1196 3 1388 1 (A, B) 192 (2-Methyl-1-chloromethylpropyl)benzene
E 62.1, IU > 200
1188 (-)
dimethylethyl)benz-
ene (3)
1316 2 (A, B) 248 1,2-Dimethyl-4-(1,1-dimethylethyl)chloro
Structure was not found 1327
benzene
1392 1 (A, B) 196 1,2-Dimethyl-4-(1,1-dimethylethyl)chloro-
Structure was not found 1331
benzene
1400 1 (A, B) 204 1,2-Dimethyl-4-(1,1-dimethylethyl)chloro
Structure was not found 1339
benzene
i
1410 1 (B)
214 1,2-Dimethyl-4-(1,1-dimethyl-2-chloroethyl)-
U 1.569, _E__7_5_._1_
1282 (-)
benzene
i
1420 2 (A, B) 224 1-Methyl-2-chlorometyl-4-(1,1-dimethylethyl) U 1.577, _E__7_3_._2_
1292 (-)
1314 (-)
benzene
i
1442 2 (A, B) 246 1-Methyl-2-chlorometyl-5-(1,1-dimethylethyl)- U 1.577, _E__7_2_._9_
benzene
1,4-Dimethyl-2-butyl- 1246 2 1420 1 (A, B) 174 1,4-Dimethyl-2-(1-chlorobutyl)benzene
U 1.510, E 71.4
U 1.483, E 68.6
U 1.434, E 68.5
1292 (-)
1298 (-)
1318 (-)
benzene (6)
1426 1 (A, B) 180 1,4-Dimethyl-2-(2-chlorobutyl)benzene
1446 2 (A, B) 200 1,4-Dimethyl-2-(3-chlorobutyl)benzene
1452 1 (A)
206 1-Methyl-2-butyl-4-chloromethylbenzene
_U__1_._4_2_0_, E 67.9i, IU > 200 1324 (-)
_U__1_._4_2_0_, E 67.0i, IU > 200 1334 (-)
_U__1_._3_3_1_, E 68.3i, IU > 200 1362 (-)
1462 1 (A, B) 216 1-Methyl-3-butyl-4-chloromethylbenzene
1490 2 (A, B) 244 1,4-Dimethyl-2-(4-chlorobutyl)benzene

Table 2. (Contd.)
Initial alkylarene
RIb
RI of reaction
products
IR
Structure assignedd
Parameters for structure Criterion
(na)
assignemente
I
(synthesis method)
(Cl CH3)
1,3,5-Trimethyl-2-(1- 1240 3 1311 1 (A, B)
1,3,5-Trimethyl-2-(1-methylethenyl)benzene
methylethyl)benzene
(4)
1389 3 (A, B) 159 1,3,5-Trimethyl-2-(1-methyl-1-chloroethyl)-
U 1.676
1267 (-)
1319 (-)
1342 (-)
benzene
1447 2 (A, B) 207 1,3-Dimethyl-2-(1-methylethyl)-5-chloromethyl- U 1.599
benzene
1470 1 (A)
230 1,3,5-Trimethyl-2-(1-methyl-2-chloroethyl)-
benzene
U 1.572
Acenaphthene (1)
1461 15 1639 1 (B)
1647 1 (B)
178 5-Chloroacenaphthene
186 4-Chloroacenaphthene
207 3-Chloroacenaphthene
245 1-Chloroacenaphthene
E 63.7
E 63.2
E 63.1
1668 1 (B)
1706 1 (B)
1578 (-)
a
Number of isomers due to substitution of nonequivalent hydrogen atoms in the molecule by a single chlorine atom.
Averaged published data.
Differences between retention indices of chlorinated products and the initial compounds here and hereinafter are given only for monochlorinated alkylarenes derivatives
and in some cases also for di- and trichlorinated substances.
The names of the products of radical chlorination into the alkyl substituents are set off by bold type.
In brackets are given experimental or calculated reference data on retention indices.
The indicated isomer is the more probable from two (more seldom from more)possible structural isomers.
The estimations by additive scheme were used.
b
c
d
e
f
g
h
i
Compounds exist as a pair of diastereomers.
The estimations of elution order by E and U values are contradictory (the value used in determination of the chromatographic elution order is underlined).

280
ZENKEVICH
simulation 300 K, averaging step 0.0003 ps, relaxa-
tion time 0.1 ps, overall simulation time (no more
than 20 ps) was selected as required the attainment
of the desired precision in estimation of E param-
eters (no more than 1 rel%, commonly less than
boiling of CCl4 (A) or water (B); however this
treatment results in increased content of dehydro-
chlorination products formed from sec- and tert-
(chloroalkyl)arenes. The degree of alkylarenes
conversion in both procedures did not exceed 10% as
estimated from the areas of the peaks on chromato-
grams.
1
1 kJ mol . The molecular geometry was preliminary
optimized by MM+ method. To accelerate the
attainment of the desired precision in E estimation
the initial period of simulation (about 1 ps) equivalent
to heating the molecule to the given temperature
300 K was excluded, and the calculations were
restarted with command RESTART. The calculation
of U parameters was performed with a simple routine
(QBasic).
The author is grateful to Cand. Chem. Sci.
E. V. Eliseenkov for useful discussion of details of
the chlorination procedures.
REFERENCES
1. Pakdell, H. and Roy, C., J. Chromatogr. A, 1994,
vol. 683, pp. 203 214.
The initial alkylbenzenes were characterized by
comparison f their two independent constants, refrac-
tion index n2D0 and retention index on the standard
nonpolar polydimethylsiloxanes (Table 2) with data
from reference books. At homophase chlorination of
alkylarenes in water-free medium (procedure A) to
20 40 l of the hydrocarbon (depending on its
molecular weight) in a flask or ampule of 2 ml
capacity was added 1 ml of 0.4 M chlorine solution
in CCl4, the mixture was maintained for 3 5 min in
the light on incandescent lamp (100 W) placed at
10 cm from the reactor, then if needed the excess
unreacted chlorine was removed by adding 0.5 ml of
10% sodium sulfite solution, the solution was
evaporated to the volume of the organic layer
approximately of 100 l, and thereto was added
20 l of the reference mixture of n-alkanes.
2. Zenkevich, I.G., J. Ecolog. Chem., 1993, vol. 2,
no. 4, pp. 258 264.
3. Zenkevich, I.G., Kharicheva, E.M., and Kosti-
kov, R.R., Zh. Org. Khim., 1999, vol. 35, no. 11,
pp. 1600 1606.
4. Dneprovskii, A.S. and Eliseenkov, E.V., Ross.
Khim. Zh., 1999, vol. 43, no. 1, pp. 57 69.
5. Vul,fson, N.S., Zaikin, V.G., and Mikaya, A.I.,
Massspektrometriya organicheskikh soedinenii (Mass
Spectrometry of Organic Compounds), Moscow:
Khimiya, 1986.
6. Zenkevich, I.G. and Ioffe, B.V., Interpretatsiya mass-
spektrov organicheskikh soedinenii (Interpretation of
Mass Spectra of Organic Compounds), Leningrad:
Khimiya, 1986.
7. The Sadtler Standard GC Retention Index Library,
Phil. Penn., 1986, vols. 1 4.
8. Pronay, A.C., J. Chromatogr., 1965, vol. 18,
pp. 586 589.
9. Bermejo, J., Blanco, C.G., and Guillen, M.D.,
J. Chromatogr., 1985, vol. 331, pp. 237 243.
10. Zenkevich, I.G. and Chupalov, A.A., Zh. Org. Khim.,
1996, vol. 32, no. 5, pp. 656 666.
11. Zenkevich, I.G., Zh. Strukt. Khim., 1999, vol. 40,
no. 1, pp. 121 130.
12. Zenkevich, I.G., Zh. Org. Khim., 1998, vol. 34,
no. 10, pp. 1463 1470.
13. Zenkevich, I.G., Zh. Org. Khim., 1992, vol. 29,
no. 9, pp. 1827 1840.
14. Moeder, M., Zenkevich, I.G., Koeller, G., and
Popp, P., Proc. 20th Int. Symp. on Capillary
Chromatogr., Italy, 1998.
15. Zenkevich, I.G., Zh. Fiz. Khim., 1999, vol. 73, no. 5,
pp. 905 910.
16. Zenkevich, I.G. and Kuznetsov, V.A., Zh. Prikl.
Khim., 1999, vol. 72, no. 8, pp. 1331 1336.
17. Stolyarov, B.V., Savinov, I.M., Vitenberg, A.G.,
Kartsova, L.A., Zenkevich, I.G., Kalmanov-
skii, V.I., and Kalambet, Yu.A., Prakticheskaya
gazovaya i zhidkostnaya khromatografiya, St. Peters-
burg: St. Petersburg. Gos. Iniv., 1999.
The heterophase chlorination (procedure B) in the
presence of water was used as comparative method
resulting in greater amounts of products originating
from ionic reactions of hydrogen replacement in the
benzene ring. This method was formerly recom-
mended for microanalytical chlorination of phenols
and hydroxybiphenyls [14]. The procedure is based
on relatively high (more than unity) distribution
factors of molecular chlorine between organic and
water phases. Into a two-phase system consisting of
2 ml of concn. HCl and 20 40 l of hydrocarbon in
a flask of 7 ml capacity within 5 min was added
100 mg of KMnO4 by portions of 10 20 mg; the
flask was under the light similar to that used in the
procedure A; the content of the flask was shaken
from time to time. After 5 min from completion of
KMnO4 addition the reaction was stopped with 2 ml
of 10% sodium sulfite solution, then was added
0.5 ml of n-heptane, and 20 l of the reference
n-alkanes mixture.
In both chlorination procedures the unreacted
chlorine can be removed by bringing the samples to
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 2 2001