Benzylation of benzene by benzyl chloride over iron mesoporous molecular sieves materials

Article abstract of DOI:10.1016/S0021-9517(03)00295-1

The alkylation of benzene with benzyl chloride has been investigated over a series of iron-containing mesoporous silicas with different Fe contents. These materials (Fe-HMS-n) have been prepared at room temperature using a route based on hydrogen bonding and self-assembly between neutral primary amine micelles (S⁰) and neutral inorganic precursors (I⁰). They have been characterized by chemical analysis, BET, XRD, and UV-vis spectroscopy. The mesoporous Fe-containing materials were very active benzylation catalysts with almost 100% selectivity to monoalkylated product and showed excellent stability. The kinetics of the benzene benzylation over this catalyst have been thoroughly investigated. A mechanism in which the reaction could be initiated by an oxidation of benzyl chloride with formation of a charge transfer complex is proposed.

Full text of DOI:10.1016/S0021-9517(03)00295-1

Journal of Catalysis 221 (2004) 55–61
www.elsevier.com/locate/jcat
Benzylation of benzene by benzyl chloride over
iron mesoporous molecular sieves materials
K. Bachari,a,b J.M.M. Millet,c,∗ B. Benaïchouba,d O. Cherifi,a and F. Figueras c
a
Laboratoire de Chimie du Gaz Naturel, Faculté de Chimie, BP 32, 16111, El Alia, U.S.T.H.B., Bab Ezzouar, Algeria
b
Centre de Recherche Scientifique et Technique en Analyses Physico-Chimiques (C.R.A.P.C.), BP 248, Alger RP 16004, Alger, Algeria
c
Institut de Recherches sur la Catalyse, CNRS, 2 av. A. Einstein, 69626 Villeurbanne cedex, France
d
Laboratoire de Valorisation des Matériaux, Université de Mostaganem, BP 227, 27000, Mostaganem, Algeria
Received 22 April 2003; revised 25 June 2003; accepted 30 June 2003
Abstract
The alkylation of benzene with benzyl chloride has been investigated over a series of iron-containing mesoporous silicas with different Fe
contents. These materials (Fe-HMS-n) have been prepared at room temperature using a route based on hydrogen bonding and self-assembly
0
0
between neutral primary amine micelles (S ) and neutral inorganic precursors (I ). They have been characterized by chemical analysis,
BET, XRD, and UV–vis spectroscopy. The mesoporous Fe-containing materials were very active benzylation catalysts with almost 100%
selectivity to monoalkylated product and showed excellent stability. The kinetics of the benzene benzylation over this catalyst have been
thoroughly investigated. A mechanism in which the reaction could be initiated by an oxidation of benzyl chloride with formation of a charge
transfer complex is proposed.
2003 Elsevier Inc. All rights reserved.
Keywords: Catalytic benzylation; Friedel–Crafts alkylation; Hammett relationship, HMS; Iron-containing mesoporous materials
1. Introduction
zylation and benzoylation of benzene with alkyl chlorides
[5,6]. They found that calcined iron sulfate and iron oxide
were excellent catalysts for the above reactions. Later, Cao et
al. [4] reported that Fe-containing zeolites or HY were also
good catalysts for the alkylation of benzene by benzyl chlo-
ride. Clark et al. [7] reported that montmorillonite-supported
zinc and nickel chlorides are highly active and selective for
the catalysis of Friedel–Crafts alkylations; in this last case
the catalytic properties of the catalysts were high enough to
warrant their commercialization [8].
In the 1990s, Mobil researchers reported the prepara-
tion of new class of silica and silica–alumina-based molecu-
lar sieves using supramolecular surfactant templates [9,10].
Originally, materials were synthesized at relatively high tem-
peratures by a cooperative organization process between
cationic surfactants (S+), namely alkyl trimethylammonium
cations with C8 to C16 chains and anionic inorganic species
(I−). Depending on the synthesis conditions, and on the
surfactant/SiO2 ratio, different phases could be obtained,
like the hexagonal phase MCM-41, the cubic one MCM-48,
and the lamellar compound MCM-50 [9,10]. Huo et al. [11]
proposed four complementary synthesis pathways. The first
Friedel–Crafts alkylations, which are usually catalyzed
by Lewis acids in the liquid phase, constitute a very im-
portant class of reactions which are of common use in or-
ganic chemistry [1]. Among these reactions, the alkylation
of benzene by benzyl chloride is interesting for the prepara-
tion of substitutes of polychlorobenzenes used as dielectrics.
This reaction is presently catalyzed in the homogeneous
phase at the industrial scale by FeCl3 [2]. The new environ-
mental legislation pushes for the replacement of all liquid
acids by solid acid catalysts which are environmentally more
friendly catalysts and which lead to minimal pollution and
waste [3,4].
The substitution of liquid acid catalysts in the case of the
Friedel–Crafts alkylation is an important challenge that is on
the way to being successful. Indeed, several solid acid cata-
lysts have already been poposed which are efficient catalysts.
Arata and co-workers investigated the Friedel–Crafts ben-
*
Corresponding author.
E-mail address: millet@catalyse.cnrs.fr (J.M.M. Millet).
0021-9517/$ – see front matter
2003 Elsevier Inc. All rights reserved.
doi:10.1016/S0021-9517(03)00295-1

56
K. Bachari et al. / Journal of Catalysis 221 (2004) 55–61
pathway involved the direct cocondensation of cationic sur-
factant (S+) with anionic inorganic species (I−) to produce
assembled ion pairs (S+I). The original synthesis of MCM-
41 silicates is a prime example of this pathway. In the sec-
ond pathway, an anionic template (S−) was used to direct
the self-assembly of cationc species (I+) through (S−I+)
ion pairs. Pathways 3 and 4 involved counterion-mediated
assemblies of surfactants and inorganic species of similar
charge. These counterion-mediated pathways produced as-
sembled solution species of type S+X−I+ or S−M+I− (with
washed with distilled water, and air-dried at 393 K. Or-
ganic molecules occluded in the mesopores were removed
by solvent extraction. The dried precursor was dispersed in
ethanol (5 g/100 ml) containing a small amount of NH4Cl
(1 g/100 ml) and the mixture was reflu+xed under vigorous
stirring for 2 h. The presence of NH4 cations in EtOH
was reported to be necessary to exchange protonated amines
formed during the synthesis and balance the excess of nega-
tive charges resulting from the substitution of FeIII for SiIV
[15,16]. The solid was then filtered and washed with cold
ethanol. The extraction procedure was repeated twice before
drying the samples at 393 K in an oven. Finally the samples
were calcined at 823 K in air for 6 h. The sample were re-
ferred to as Fe-HMS-n where n was the Si/Fe ratio in the
precursor gel.
X
− = Cl− or Br− and M+ = Na+ or K+). In 1994, a new
pathway was proposed by Tanev et al. [12] to prepare meso-
porous silicas at room temperature by a neutral templat-
ing route (S0I0). In this case, the organic surfactant is not
quarternary ammonium cation but a primary amine, and the
assembly involves hydrogen-bonding interactions between
neutral primary amines and neutral inorganic precursors.
These materials, denoted HMS (hexagonal mesoporous sil-
ica), exhibit excellent catalytic ability for macromolecular
reactions and offer new opportunities for transition metal in-
corporation into silica frameworks [13,14].
In the present paper, we report the synthesis and charac-
terization of such materials incorporating iron and their test
as catalysts for the benzylation of benzene with benzyl chlo-
ride. The kinetics of the reaction over these catalysts have
been investigated and the reaction has been extended to other
substrats like toluène, p-xylene, anisole, and naphthalenic
compounds.
2.3. Characterization of the samples
The chemical compositions of the samples were deter-
mined by atomic absorption and their surface areas deter-
mined using the BET method. X-ray diffraction (XRD) pat-
terns were obtained using a SIEMENS D500 diffractometer
and Cu-Kα radiation. They were recorded with 0.02◦ (2θ)
steps and 1 s counting time per step over two angular do-
mains from 1 to 10◦ (2θ) and from 10 to 80◦ (2θ). UV–vis
spectra were collected on a Perkin-Elmer Lambda 9 spec-
trometer.
2.4. Catalytic testing
2. Experimental
The alkylation of benzene by benzyl chloride has been
used as a model reaction for Friedel–Craft alkylation ca-
talytic properties. The reaction was carried out in a batch
reactor between 333 and 363 K. The amount of 100 mg
of the solids was tested after an activation consisting of a
heat treatment under air (2 L h−1) up to 573 K with vari-
ous heating rates. Immediately after cooling, the catalysts
were contacted under stirring with a solution of 25 ml of
benzene and 6.48 or 2.16 ml of benzyl chloride to obtain a
benzene to benzyl chloride mole ratio of 5 or 15. The conver-
sion of benzyl chloride was followed by analyzing samples
of the reaction mixture collected at regular intervals by gas
chromatography using a gas chromatograph equipped with a
flame ionization detector FID and a capillary column RTX-1
(30 m × 0.32 nm i.d.) The selectivity is expressed by the
molar ratio of formed diphenylmethane to converted benzyl
chloride.
2.1. Materials
Samples were synthesized with hexadecyltrimethylam-
monium bromide (Aldrich Ref. 85,582-0), hexadecylamine
(Aldrich Ref. 44,531-2), tetraethyl orthosilicate (Aldrich
Ref. C13,190-3), ferric nitrate Fe(NO3)3·9H2O (Merck Ref.
103883), and ethanol RP (Prolabo Ref. 20.821.296).
2.2. Catalyst preparation
The catalysts have been prepared using a protocol re-
ported by Tanev et al. [12]. In a typical preparation, hexade-
cylamine (HDA) was added to a solution containing water
and ethanol (EtOH). The mixture was stirred until it was
homogeneous and then tetraethyl orthosilicate (TEOS) was
added under vigorous stirring. Ferric nitrate was dissolved
in an HDA/water/ethanol solution before addition of TEOS.
After mixing, the resulting solution had the following com-
position [15]:
3. Results and discussion
3.1. Characterization
SiO2-(1/2n)Fe2O3–0.3HDA–7EtOH–35H2O,
with n = 100, 50, 44, 30, 15.
This solution was then stirred at room temperature for
24 h. The obtained solids were recovered by filtration,
The results of the chemical analysis and the BET surface
area measurements of the catalysts are given in the Table 1.
The iron contents of the solids corresponded relatively well

K. Bachari et al. / Journal of Catalysis 221 (2004) 55–61
57
Table 1
Chemical analysis and BET surface area measurements data
Sample
Chemical analysis
Surface area
2
−1
)
Fe (wt%)
Si/Fe
(m g
HSM
0.0
0.0
80.0
54.6
42.5
23.8
14.0
1170
1162
1135
1106
935
Fe-HMS-100
Fe-HMS-50
Fe-HMS-44
Fe-HMS-30
Fe-HMS-15
0.75
1.66
2.12
3.7
6.08
698
◦
Fig. 2. XRD patterns of the Fe-HMS-n catalysts in the domain of 10–80
(2θ). n = Si/Fe = (a) 100, (b) 50, (c) 44, (d) 30, (e) 15.
◦
Fig. 1. XRD patterns of the Fe-HMS-n catalysts in the domain of 1–10
(2θ). n = Si/Fe = (a) 15, (b) 30, (c) 44, (d) 50, (e) 100.
to those fixed for the synthesis except at low iron content
(Fe-HMS-100) where a small excess of iron was observed.
Most of the values of the specific surface areas of the solids
were larger than 1000 m2 g−1, which is typical of meso-
porous materials [12,16]. When the iron content increased,
they decreased slightly first and then more drastically at high
iron loading (Fe-HMS-30 and -15).
The X-ray powder diffraction patterns of the solids
showed a broad peak at d = 32 Å (Fig. 1) characterizing a
mesoporous material not well crystallized. The intensity of
the peak decreased when the iron content increased show-
ing that the addition of iron has a negative effect on the
crystallinity. At the same time, small peaks corresponding
to αFe2O3 (hematite form) appeared in the 10 to 80◦ (2θ)
range and grew with the iron content (Fig. 2).
The UV-spectra of the samples Fe-HMS-100, -50 and
-15 are reported in Fig. 3. The spectrum of Fe-HMS-100
catalyst showed two absorption bands at 230 and 245 nm
corresponding to oxygen to metal charge transfers involv-
ing isolated tetrahedrally coordinated ferric cations. When
the iron content of the solids increased, a very broad band
Fig. 3. Diffuse reflectance UV–vis spectra of the Fe-HMS-n catalysts.
n = Si/Fe = (a) 100, (b) 50, (c) 15.
appeared with a maximum around 350 nm. The presence of
this band, which is characteristic of iron oxide, was in good
agreement with the XRD data.
3.2. Reaction kinetics
The kinetic data for the benzene benzylation reaction in
excess of benzene (stoichiometric ratio PhH/BnCl = 15)

58
K. Bachari et al. / Journal of Catalysis 221 (2004) 55–61
Table 2
Table 3
Influence of the stoichiometric ratio between benzene and benzyl chloride
for benzene benzylation reaction at 348 K over Fe-HMS-50 catalyst
Catalytic activitiy of Fe-HMS-50 at different temperatures
a
Temperature
(K)
Time
(min)
Diphenylmethane
selectivity (%)
Apparent rate constant
K (×10 min
a
a
4
−1
Benzene to benzyl
chloride ratio
Time
(min)
Diphenylmethane
selectivity (%)
)
373
378
383
135
60
100
95
121
155
318
5
15
350
245
65.6
100
30
73.6
a
a
Time required for the complete conversion of benzyl chloride.
Time required for 50% conversion of benzyl chloride.
Fig. 5. Arrhenius plot of log K as a function of (1/T ) for the benzene
a
benzylation reaction over Fe-HMS-50 catalyst.
Table 4
Fig. 4. Effect of reaction temperature on the conversion of benzyl chloride
in the benzene benzylation reaction over Fe-HMS-50 catalyst at 343 (F),
348 (2), and 353 K (Q).
Reaction rates for substituted benzenes
Benzene Toluene p-Xylene Anisole Chlorobenzene
4
−1
)
K ×10 (min
318
291
275
222
247
a
over the Fe-HMS-50 catalyst could be fitted well to a
pseudo-first-order rate law,
results showed that the catalytic performances of the cat-
alyst strongly increased with the reaction temperature. In-
deed, the time for 50% conversion of benzylchloride and
the apparent rate constant Ka changed from 135 min and
121 × 10−4 min−1 at 343 K to, respectively, 30 min and
318 × 10−4 min−1 at 353 K. By contrast, the selectivity to
diphenylmethane decreased from 100 to 73.6%. The first-
order rate constants (Ka) at the different temperatures cal-
culated from these curves are reported in an Arrhenius plot
in Fig. 5. The activation energy estimated thus obtained was
log[1/1 − x] = (ka/2.303)(t − t0),
where ka was the apparent first-order rate constant, x the
fractional conversion of benzyl chloride, t the reaction time,
and t0 the induction period corresponding to the time re-
quired for reaching equilibrium temperature. A plot of
log[1/1 − x] as a function of the time gave a linear plot
over a large range of benzyl chloride conversions.
Two PhH/BnCl ratios have been investigated. The results
obtained are reported on Table 2. It appeared that the stoi-
chiometric ratio between benzene and benzyl chloride has a
strong influence on the selectivity to diphenylmethane. With
a low ratio, the secondary reactions to dibenzylbenzenes and
tribenzylbenzene were favored. A ratio of 15 between the
two reactants, which corresponded to an excess of benzene,
has thus been used to study the influence of the other para-
meters and particularly for the reaction kinetics study.
The effect of temperature on the rate was studied by con-
ducting the reaction at 343, 348, and 353 K under the stan-
dard reaction conditions (stoichiometric ratio PhH/BnCl =
15 and 0.1 g catalyst). The kinetic curves are shown in
Fig. 4 and the selectivities calculated in Table 3. The
97 kJ mol−1
.
The effect of substituents was investigated using differ-
ent aromatic substrates. The results obtained are reported
on Table 4. If the reaction was acid catalyzed a correla-
tion of the Hammett +type would have been expected, i.e.,
logKa = logKa + σ ρ, in which Ka is the rate constant
0
0
for benzene and σ+ a coefficient representing the change of
reactivity due to the substituent, and ρ a constant related to
the charge on the intermediate complex [17]. For example,
in acid-catalyzed reactions such as the alkylation of substi-
tuted benzenes with a tetramer of propylene (MeCH:CH2)4
and anhydrous AlCl3 giving C12H25, the reactivity of aro-
matics bearing various substituents was in the order OMe >

K. Bachari et al. / Journal of Catalysis 221 (2004) 55–61
59
Table 5
Effect of water on the catalytic properties of Fe-HMS-50 at 353 K
Water
content (min)
(vol%)
Time Benzyl chloride
Diphenyl-
methane selectivity
(%)
Apparent rate
constant
conversion
(%)
4
−1
(×10 min
)
–
400
420
520
610
720
720
720
99
99
99
98.5
68
73.6
73.9
70.7
66
62.5
60
318
298
219
139
90
0.10
0.20
0.30
0.50
0.65
0.80
57.6
48.7
52
33
58.5
Fig. 6. log K for the benzene benzylation reaction over Fe-HMS-50 ca-
a
talyst as a function of the ionization potential tabulated for the different
substrates [21]. 1, Benzene; 2, toluene; 3, p-xylene; 4, mesithylene; 5, chlo-
robenzene; 6, anisole.
Me > H, while alkylation of a Cl-substituted ring proceeds
only to a small extent [18].
In the present case, only a small change of Ka was ob-
served and the rate constants remained in the same range
within 20%. This suggested a mechanism different from the
usual acid mechanism. It has been proposed earlier that the
reaction could be initiated by an oxidation of benzyl chloride
with formation of a charge transfer complex. This mecha-
nism could be described as
Fig. 7. Effect of moisture on the initial reaction rate (mol/L/min) at 353 K
in the benzylation of benzene over Fe-HMS-50 catalyst.
+.
φ-CH2Cl + Fe3+ → φ-CH2 + Cl·,
·
+.
φ-CH2 → φ-CH2+ + Fe2+
,
·
size of the substituting group of the studied aromatic com-
pounds. Using the Es parameter tabulated by Charton [22]
we have shown that such a relation did not exist.
Fe2+ + Cl· → Fe3+ + Cl−.
It was interesting to compare the solids with Fe-ex-
changed clays investigated earlier under similar conditions
(PhH/BnCl = 15, 353 K). Both systems reached a final con-
version of 100% with complete selectivity to monoalkyl; the
half reaction time was 10 min for Fe/K10 and was here about
20 min, so that Fe-MCM is less active than clays probably
due to the higher amount of iron in the latter system. They
are more active than dealuminated Y zeolites with a half re-
action time 50 min against 112 for a PhH/BnCl ratio = 5.
The final conversion reached here was 100% so that the final
selectivity is lower, 65.6 against 94.2 for Y zeolites [23].
This mechanism, which was first proposed to rationalize the
catalytic properties of exchanged clays [19], has later been
supported by the observation that thallium oxide, a solid
base was an active alkylation catalyst [20]. Indeed the rate
constant here was more directly related+to the ionization po-
tential of the substrates rather than to σ as shown in Fig. 6
[21]. The later figure shows a linear relation between the ion-
ization potential and logKa considered for all the substrates
except chlorobenzene. In the case of chlorobenzene, the slow
step was apparently not the the ionization of chlorobenzene
but a subsequent step:
φ-CH2+ + ArH → φ-CH2–ArH+,
φ-CH2–ArH+ → φ-CH2–Ar + H+.
In order to rule out the influence of a sterric effect on the
rate of reaction, we have applied the Taft relation [17]. Ac-
cording to this relation when a sterric effect influences the
reaction, there is a linear relation between the rate and the
parameter Es values considered to be representative of the
3.3. Effect of water
Lewis acids are sensitive to water and the effects of water
on the catalytic activity were investigated using Fe-HMS-
50 at 353 K with a ratio PhH/BnCl = 15, adding different
amounts of water. The results are reported in Table 5 and
in Fig. 7. A small addition of water had almost no effect
on the catalytic properties of the compound whereas a larger

60
K. Bachari et al. / Journal of Catalysis 221 (2004) 55–61
Table 6
Table 8
Catalytic properties of the catalysts in the benzylation of benzene with ben-
zyl chloride at 348 K
Effect of recycling of the catalysts in the benzylation of benzene with benzyl
chloride at 353 K
a
a
Catalyst
Time
(min)
Diphenylmethane
selectivity (%)
Apparent rate constant
Catalyst
Time
(min)
Diphenylmethane
selectivity (%)
Apparent rate constant
4
−1
4
−1
K (×10 min
)
K (×10 min
)
a
a
HSM
–
–
245
185
120
90
–
–
–
Fresh
First reuse
Second reuse
400
400
400
98.9
98.5
97.3
318
307
296
Fe-HMS-100
Fe-HMS-50
Fe-HMS-44
Fe-HMS-30
Fe-HMS-15
–
100
100
98.3
87.2
155
333
374
800
a
Time required for the complete conversion of benzyl chloride.
Table 9
Reaction rates for substituted naphthalene
a
Time required for the complete conversion of benzyl chloride.
Substituent
4
Naphthalene Methylnaphthalene Methoxynaphthalene
Table 7
−1
K ×10 (min
a
)
146
138
106
Influence of the pretreatment heating rate on the catalytic properties of the
Fe-HMS-50 catalyst. The reaction temperature was 353 K and the ratio be-
tween benzene and benzyl chloride 15
result confirms that the resulting Fe oxide is more active that
isolated Fe cations.
a
Calcination
Time
(min)
Diphenylmethane
selectivity (%)
Apparent rate constant
4
−1
K (×10 min
)
a
Slow
Fast
620
400
74
73
130
318
3.5. Recycling of the catalysts
a
Time required for the complete conversion of benzyl chloride.
The stability of the catalysts has been studied by running
the reaction successively with the same catalyst (Fe-HMS-
50) under the same conditions without any regeneration be-
tween two runs. The reaction was first run under the standard
conditions (benzene to benzyl chloride ratio of 15, 353 K)
to the complete conversion of benzyl chloride. Then after a
period of 8 min another quantity of benzyl chloride was in-
troduced in the reaction mixture leading to the same benzene
to benzyl chloride ratio. After the completion of the second
run, the same protocol was repeated a second time. The re-
sults, presented in Table 8, showed that the catalyst could be
used several times in the benzene benzylation process with-
out a significant change of its catalytic activity.
addition had a drastic one with a decrease both of the activity
and of the selectivity. Similar results have been obtained on
supported thallium [24] or indium oxides [25].
3.4. Catalytic performance of Fe-MCM materials in the
Friedel–Crafts alkylation
A comparison of the catalytic properties of the solids
tested are presented on Table 6. The pure silicic compound
(HMS) and the compound containing less iron (Fe-HMS-
100) were totally inactive. The other compounds showed an
activity increasing with their iron content. However, the se-
lectivity to diphenylmethane at complete conversion of ben-
zyl chloride decreased while the Fe content increased. The
best catalyst appears thus to be Fe-HMS-44.
The characterization of the compounds by UV–vis spec-
troscopy clearly showed that contrary to the other catalysts,
Fe-HMS-100 contained only isolated iron species. These
species should thus be inactive. This is in good agreement
with previous results obtained on Fe-hydrotalcite showing
that these species were inactive in the reduction of nitro aro-
matic compounds by hydrazine hydrate [26]. Furthermore,
it was shown that these species could not have been reduced
by hydrazine. The same observation had been made in the
case of Fe-sulfated zirconia used in gas phase n-butane iso-
merization [27]. These results tend to confirm the proposed
mechanism.
3.6. Applications to other aromatic alkylations
The Fe-HMS-50 catalyst has been used with success for
the alkylation of benzenic compounds as illustrated in Fig. 6
and discussed above. More interesting is the observation that
this catalyst is always active and selective for larger mole-
cules like naphthenic compounds such as methoxynaphtha-
lene (Table 9 and Fig. 8). The large pores of the mesoporous
support permit the conversion of these molecules that could
not be done on other supports.
4. Conclusion
In conclusion, Fe-MCM are active catalysts for alkyla-
tions. In contrast to usual Lewis acids they show a low sensi-
tivity to water and can easily be regenerated by calcinations.
These properties are linked to the mechanism which involves
a redox step at the reaction initiation. This gives a greater in-
dependence to the effect of substituents, and these catalysts
can therefore be used with substrates of low reactivity. Fur-
thermore, the large pores of the mesoporous catalyst do not
The effect of the pretreatment duration of the catalyst has
been studied by varying the calcination time at 573 K of the
Fe-HMS-50 compound from 50 to 180 min. It can be seen
in Table 7 that a fast calcination time led to more active ca-
talysts without affecting the selectivity to diphenylmethane.
Fast calcination induces self steaming of the sample and the

K. Bachari et al. / Journal of Catalysis 221 (2004) 55–61
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Fig. 8. Effect of substituents on the naphthalene ring on the conversion
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naphthalene (F), methylnaphthalene (2), and methoxynaphthalene (Q).
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