738
J. Phys. Chem. 1985,89, 738-742
Reactions of Aromatic Molecules in the Interlayer of Transition-Metal Ion-Exchanged Montmorillonite Studied by Resonance Raman Spectroscopy. 2. Monosubstituted Benzenes and 4,4’-Disubstltuted Biphenyls Y. Soma,* M. Soma, National Institute for Environmental Studies, Yatabe, Tsukuba, Ibaraki 305, Japan
and I. Harada Pharmaceutical Institute, Tohoku University, Aobayama, Sendai 980, Japan (Received: June 19, 1984; In Final Form: August 24, 1984)
The adsorption and reaction of monosubstituted benzenes and related 4,4’-disubstituted biphenyls in the interlayer of transition-metal (Cu2+,Fe3+,Ru3+)ion-exchanged montmorillonite have been investigated by resonance Raman spectroscopy. 4,4-Disubstituted biphenyls (dimethoxybiphenyl,dihydroxybiphenyl)and monosubstituted benzenes (anisole, halogenobenzene, toluene, phenol) are oxidized by transition-metal ions in the interlayer under a dry atmosphere to their cation radicals which are stable enough to allow measurement of resonance Raman spectra by a conventional method. Monosubstituted benzenes which have low ionization potentials further dimerize to form cation radicals of the 4,4’-disubstituted biphenyl type, the latter being characterized by an absorption band around 600 nm and identified specifically by the presence of an inter-ring CC stretching Raman band. This approach has essentially confirmed earlier observations and gives a more unified scheme for the reaction of benzene derivatives in the interlayer of the transition-metal ion-exchanged montmorillonite, based on the direct identification of the adsorbed species.
Introduction Mortland, Pinnavaia, and their co-workers have found that the adsorption of certain aromatic molecules on montmorillonites whose exchangeable cations are saturated with transition-metal ions leads to the formation of colored complexes. The IR spectrum of the so-called type 11benzene complex formed under dry conditions indicates that the chemical state of the adsorbed benzene is remarkably different from those of adsorbed alkyl-substituted benzenes such as toluene and ~ y l e n e , while ~ - ~ adsorbed anisole is reported to dimerize to 4,4’-dimethoxybiphenyI.’ The essential step in the formation of these colored complexes has been shown to involve an electron transfer from the adsorbed organic molecules to the interlayer transition-metal ion, notably by ESR spectros~ o p y . ~However, -~ detailed spectroscopic information concerning the structure of adsorbed species has not been sufficient. The type I and I1 species of the adsorption complexes of benzene are characterized by their visible absorption ~ p e c t r a .The ~ type 1 species has an absorption band around 370 nm and the type I1 species has a band around 500 nm and a longer wavelength band extending into the IR region. In previous papers,’**we have shown from resonance Raman and ESR spectroscopic studies that the type I1 benzene is actually the poly-p-phenylene cation and the type I benzene is the reduced form of poly-p-phenylene. For pdimethoxybenzene adsorption, only the monomeric cation radical is d e t e ~ t e d . ~Therefore, it is suggested that the formation of a cation (radical) is followed by para polymerization for benzene while the latter process is inhibited for p-dimethoxybenzene. In the study of adsorption where several kinds of adsorbed species exist, resonance Raman spectroscopy is often useful in offering selective information on the relevant species if the ex(1) (2) (3) (4)
Part 1, Soma, Y.; Soma, M.; Harada, I. J. Phys. Chem.1984,88,3034. Mortland, M. M.; Pinnavaia, T. J. Nature (London) 1971, 229, 75. Pinnavaia, T. J.; Mortland, M. M. J. Phys. Chem. 1971, 75, 3957. Pinnavaia, T. J.; Hall, P. L.; Cady, S. S.; Mortland, M. M. J. Phys.
Chem. 1974, 78, 994. (5) Rupert, J. P. J . Phys. Chem. 1973, 77, 784. (6) Pinnavaia, T. J. In “Catalysis in Organic Synthesis 1977”; Smith, G. V., Ed.; Academic Press: New York, 1977; p 131. (7) Fenn, D. B.;Mortland, M. M.; Pinnavaia, T. J. Clays Clay Miner. 1973, 21, 315. (8) Soma, Y.; Soma, M.; Harada, I. Chem. Phys. Lett. 1983, 99, 153. (9) Soma, Y.; Soma, M.; Harada I. Chem. Phys. Lett. 1983, 94, 475.
0022-3654/85/2089-0738$01.50/0
citation wavelength of laser light is properly chosen. Accordingly, determination of the structure of the adsorbed species by resonance Raman spectra can be more straightforward than by IR spectra which may be complicated by the coexistence of several adsorbed species as well as by substrate material. In this report we have studied the resonance Raman spectra of several monosubstituted benzenes and 4,4’-disubstituted biphenyls adsorbed on the transition-metal ion-exchanged montmorillonites and propose unified mechanisms of the formation of colored species and their reactions.
Experimental Section The preparation of the metal (Cu2+,Fe3+, Ru3+, Ca2+,Cr3+) ion-exchanged montmorillonites and the sample preparation for the measurements of Raman, IR, and ESR spectra were described in previous paper^.',^!^ Raman spectra with 610.0-nm excitation were recorded on a Jasco R-800 Raman spectrometer equipped with a rhodamine 6G dye laser excited by an Ar ion laser. Chlorobenzene, fluorobenzene, anisole, phenol, benzonitrile, toluene, and 4,4’-dihydroxybiphenyl of guaranteed quality were purchased from Wako Chemical Ind. and used as received. 4,4’-Dimethoxybiphenyl (4,4’-DMOBP) was synthesized and supplied by Dr. H. Sakuragi of the University of Tsukuba. In the adsorption of solid compounds such as phenol, 4,4’DMOBP, or 4,4’-dihydroxybiphenyl, the montmorillonite sample (film or powder) was immersed in a cyclohexane solution saturated with the adsorbate and dried in a P 2 0 5desiccator (method I in Table I). The liquid compound (the adsorbate) in a small vessel was put in the desiccator and its vapor was allowed to adsorb on the clay sample (method 11). Typical conditions for the adsorption, colors, and the rate of the formation of complexes, for Cu2+-montmorillonite, are listed in Table I. Results and Discussion 4,4’-Dimethoxybiphenyl. The absorption spectrum of 4,4’DMOBP adsorbed on a Cu2+-montmorillonitein a dry atmosphere is shown in Figure la. The spectrum consists of a strong band at about 400 nm and a broader band ranging from 550 to 850 nm, with accompanying structures at (390, 401, 418, 431) and (715, 800) nm, respectively. This spectral pattern is quite similar to that of the 4,4’-DMOBP cation radical produced by y-ray 0 1985 American Chemical Society
The Journal of Physical Chemistry, Vol. 89, No. 5, 1985 739
Reaction of Substituted Benzene on Montmorillonite
TABLE I: Condition of Adsorption and the Reaction Rate of Aromatic Molecules on Cu*+-Montmorillonite and the Color of the Complexes Formed adsorption
adsorption temp
. methoda I1 I1 I1 I, I1 I1 I1 I I
chlorobenzene fluorobenzene anisole phenol toluene benzonitrile 4,4'-dimethoxybiphen yl
4,4'-dih ydroxybiphenyl
reaction rateb
color of the complex
++
RT RT RT RT RT RT RT RT
yellow, pale green yellow, pale green dark blue yellow dark brown‘ brown yellow pale yellow dark green green
++ +++
-
+++ ++ + +++ ++
@Montmorillonitewas brought into contact with the adsorbate solution (I) or with the adsorbate vapor (11) (see text). b+++, fast, deep coloration appreciable to slow, color develops within a couple of days; very slow, faint color appears in several days. eThe color darkens within a day; with time.
++,
MeO@-@OMe
+,
ads.
(dark blue)
H20 vapor
b
1201
19
300
400
@OMe
500
ads,
(dark blue)
600
(tan)
~20vapor
700
800
I
QOOnm
- -
(green blue) (darkblue) p205 H20mpor e desiccator
819
I
1282
M . O ~ M .
808
p0Wd.r
1194
729
(48SOA)
e 300
400
500
600
700
800
000nm
Figure 1. Absorption spectra of 4,4’-dimethoxybiphenyl and anisole adsorbed on Cu2+-montmorillonite under a dry atmosphere and the spectral changes under the influence of water vapor.
radiolysis in a freon matrix, Le., (385, 397, 414,427) and (728, 813) nm a t 77 K.Io Accordingly, the cation radical of 4,4’DMOBP is formed in the interlayer of the montmorillonite in a dry atmosphere. This cation radical (species I) reacts readily with water vapor to leave another colored species (species 11) which gives a structureless spectrum as shown in Figure 1b. The latter spectrum agrees with the “type 11, 4,4’-DMOBP” on V02+hectorite.“ Under the conditions in which the spectrum of species I1 is observed, a significant part of the Cu ion remains reduced and a signal from an organic radical with a slightly different line width is observed in ESR measurement. This implies that species 11 is also cationic. The resonance Raman spectra of species I with 457.9- and 610.0-nm excitation are shown in Figure 2, a and b. Both spectra are simple and all the bands appear to correspond between the two. This observation indicates strongly that the two absorption bands in Figure l a originate from the same chemical species. It is noticed that the relative intensities of Raman bands in Figure (10) Shida, T., private communication. (1 1 ) Ernstbrunner, E.; Girling, R.B.; Grossman, W. E. L.; Hester, R. E. J . Chem. Soc., Perkin Tram. 2 1978, 177.
Figure 2. Raman spectra of 4,4’-dimethoxybiphenyl adsorbed on Cu*+-montmorillonite and of 4,4’-dimethoxybiphenyl: (a) 4,4‘-DMOBP on Cu2+-montmorillonite with 457.9-nm excitation; (b) with 610.0-nm excitation; (c) 4,4’-DMOBP powder with 488.0-nm excitation. Dotted lines represent the overlapping Ar spontaneous emission lines.
2 are different from each other, Le., the band at 1619 cm-’ is very strong with 457.9-nm excitation while that at 1343 cm-’ is strong with 610.0-nm excitation. The difference in the intensity distribution in the two spectra is due to the difference in excitation profiles of the vibrational bands. Figure 2c shows the Raman spectrum of 4,4’-DMOBP. Frequency differences between 4,4’-DMOBP and species I in most of the bands are small but the frequency shift of the inter-ring CC stretching band from 1282 (4,4’-DMOBP) to 1343 cm-’ (species I) is remarkable. The resonance Raman spectra of species I resemble those of the benzidine cationI2 and biphenyl anion (See Figure 6, f and h).13 The high-frequency shift of the inter-ring C C stretching bands have been observed also for benzidine and biphenyl a s their neutral forms convert to cation or anion radicals, and the results have been explained by an enhanced contribution of the quinoid structure t o the radi~a1s.I~Moreover the behavior in excitation profiles ~
~
(12) Hester, R. E.; Williams, K. P. J. J . Chem. SOC.,Faraday Trans. 2 1981, 77, 541. (13) Aleksandrov, I. V.;Bobovich, Ya. S.; Maslov, V. G.; Sidorov, A. N. Opt. Spectrosc. (Engl. Trawl.) 1975, 38, 387. (14) Takahashi, C.; Maeda, S . Chem. Phys. Lett. 1974, 24, 584.
740 The Journal of Physical Chemistry, Vol. 89, No. 5, 1985
Soma et al.
TABLE II: Observed Raman Bands (cm-') of 4,4'-Dimetboxybiphenyl Adsorbed and 4,4'-Dimethoxybiphenyl Formed from Anisole on Cu-Montmorillonite
1608
1619 1528
1616
1194
1207
1529 1323 1209
1032
99 1 819
998 824
1531 1282
1343
819
1618 1528 1325 inter-ring CC str 1208 CH in-plane def
995 (825)
11588
1617
1
I
825
1325
C)
1602 1304 x112
1700
1500
1000
500
cm-'
Figure 3. Raman spectra of anisole adsorbed on Cuz+-montmorillonite and of liquid anisole: (a) adsorbed anisole with 457.9-nm excitation; (b) with 610.0-nm excitation; (c) liquid anisole with 514.9-nm excitation. In
spectrum (a), the background due to a broad emission band was subtracted. of the Raman bands mentioned above is similarly observed for the biphenyl a n i ~ n . ' ~Accordingly, ,'~ though the resonance Raman spectra of the authentic 4,4'-DMOBP cation radical (e.g. in a freon matrix) are not available, both the resonance Raman and visible spectra of species I would be explained satisfactorily as those of 4,4'-DMOBP cation radical. The Raman spectrum of species I1 is practically the same as that of species I (Table 11) except for the inter-ring C C band at 1323 cm-' which is 20 cm-' lower than the corresponding band of species I. Thus species I1 is assigned to the 4,4'-DMOBP cation with surroundings different from those of species I. Species I1 presumably has a strong interaction with the surroundings (e&, the 4,4'-DMOBP molecule, the Cu+ ion, and the silicate layer), which causes it to give a structureless visible spectrum and the weaker inter-ring C C bond (reduced quinoid structure) and protects it against reaction with water. Species I is more susceptible to water and readily reduced to neutral 4,4'-DMOBP. Anisole. The absorption spectrum of anisole adsorbed on Cu2+-montmorillonite in a dry atmosphere is shown in Figure IC. When this sample is exposed to humid atmosphere the color becomes tan. When desiccated again, the sample becomes (IS) Thomas, J. M.;Adams, J. M.; Graham, S.H.; Tenakoon, D. T. B. In 'Solid State Chemistry of Energy Conversion and Storage"; Gocdenough, J. B., Whittingham, M. S.,Eds.; American Chemical Society: Washington, DC 1977;Adv. Chem. Ser. No. 163,Chapter 17.
1700
1500
1000
800
cm
-1
Figure 4. Resonance Raman spectra of anisole adsorbed on Cu2+-
montmorillonite with 457.9-nm excitation: (a) Cu2+-montmorillonite exposed to anisole vapor for 1 day; (b) for 10 days; (c) the ratio of the interlayer ions, Cu2+to Na+, is 1/8 in this montmorillonite. In each spectrum the background due to a broad emission band was subtracted. green-blue (Figure Id). If the sample is exposed to humid air once again, the sample gives the spectrum shown in Figure le. This behavior is largely the same as those reported for anisole adsorbed on Cu2+-,Fe3+-, and V02+-exchanged hect~rites.~.'If we compare Figure 1, d and e, with Figure 1, a and b, it is apparent that species I and I1 (4,4'-DMOBP cation radicals) are formed during the above treatments. The resonance Raman spectrum of the adsorbed anisole shows that the main colored species in Figure IC should be species I1 and the anisole cation (see below). However, the long wavelength band is stronger than expected from the spectrum of species I1 (the anisole cation has no absorption in this region). We tantatively attribute this behavior to the existence of an unspecified neutral species-cation association. Parts a and b of Figure 3 are the resonance Raman spectra of adsorbed anisole under the conditions corresponding to that which gives Figure IC. Figure 3b is essentially the same as that of species I1 with 610.0-nm excitation (Table 11). On the other hand, Figure 3a is an overlap of the spectrum of species I1 (shaded bands in Figure 3a) and another spectrum. The latter spectrum is not the same as that of liquid anisole but has a resemblance to it. The characteristic features of the resonance Raman spectra of cation radicals of disubstituted benzenes with 457.9-nm excitation, as observed in the case of p-dimethoxybenzene:," are that the shifts in frequencies from those of the neutral molecule are rather small but the relative intensities change significantly, e.g., the ring stretching band around 1600 an-'appears very strong in the cation
The Journal of Physical Chemistry, Vol. 89, No. 5, 1985 741
Reaction of Substituted Benzene on Montmorillonite radical spectrum. Since these effects are observed in the present spectrum, it is probable that the spectrum is due to a cation radical of anisole. The ratio of the amount of anisole cation to that of species I1 changes with the adsorption conditions as can be understood from the Raman spectra shown in Figure 4. Figure 4a is the spectrum of a Cu2+-montmorillonite sample, which has been kept exposed to anisole vapor in a dry atmosphere for 1 day and Figure 4b is that of a sample kept for 10 days under the same conditions. Figure 4c is the spectrum of a sample in which the Cu2+ion has been partially exchanged, Le., one-eighth of the exchangeable cations are Cu2+and the remaining cations are sodium ions. The relative amount of species I1 in Figure 4b is evidently more than that in 4a and only the 4,4’-DMOBP cation is observed in 4c. Thus it is suggested that an anisole cation having enough room to accommodate neutral anisole in its neighboring sites reacts to form the 4,4’-DMOBP cation. If we summarize the behavior of adsorbed anisole and 4,4’-DMOBP, the following reactions are supposed to occur in the interlayer of the montmorillonite, which is consistent with the mechanism proposed by Fenn et al.’ (see below):
Cu’ t ( M e O ( O t ( O ) O M e ) \
-
-
/Q OMo/Cu-mont.
-A
-620
d”\
(1)
I
I1
(8)
I1
/Cu-m.
I
t
I Species I1 formed in the adsorption of anisole is less stable toward moisture than the species formed in the adsorption of 4,4’DMOBP. Raman scattering of anisole or 4,4’-DMOBP adsorbed in the neutral form is too weak to be detected because of the off-resonant condition. Fenn and others investigated the adsorption of anisole on Cu2+-hectorite.’ They observed several adsorbed species by IR spectroscopy and suggested the formation of 4,4’-DMOBP based on the I R spectra of adsorbed 4,4’-DMOBP and a mass spectroscopic analysis of the product. o u r “in situ” observation by Raman spectroscopy has shown that their “blue, type I1 anisole” includes the anisole cation and the 4,4’-DMOBP cation (species 11) and that the “green, type I1 4,4’-DMOBP” is species I1 of the 4,4’-DMOBP cation. Adsorption of Other Monosubstituted Benzenes. Absorption spectra of some monosubstituted benzenes adsorbed on Cuz+- or Fe3+-montmorillonite are shown in Figure 5 . The 457.9-nm excited resonance Raman lines of these and related compounds are represented in Figure 6. In addition to a common band in the 400-463-nm range, another band is observed in the long wavelength region (580-670 nm) except in Figure 5e. The latter band map be considered to be due to a cation radical of the biphenyl type by analogy with adsorbed 4,4’-DMOBP and anisole, while both monomeric and dimeric (biphenyl type) cations contribute to the shorter wavelength band. In fact, a Raman band near 1300 cm-’, assignable to the inter-ring C C stretching vibration, is observed in all of those samples except for adsorbed toluene (Figure 6). Accordingly, the existence of both an absorption band at 580-670 nm and a Raman band near 1300 cm-’ provides a good diagnosis of the formation of the dimeric cation from the adsorbed substituted benzenes. For instance, chlorobenzene (fluorobenzene) adsorbed on Fe3+- (or Ru3+-) montmorillonite has a broad absorption at 580 nm and
II
I.
I
L
PhF/Fo-m.
I
l
Ill
l
I
I
( 0 ) PhYo/Cu-m..
YeOCh-PhOYo (,)
(0)
I
/Cu-m. HOPh-PhOH /Cu-m.
I
I I
1so0
I
I#II
I
1000
500 cm”
Figure 6. Resonance Raman spectra of adsorbed monosubstituted benzenes and 4,4’-disubstituted biphenyls with 457.9-nm excitation. The spectrum of the biphenyl anion is taken from ref 13.
gives a Raman band at 1368 cm-I which is not due to the parent molecule. Common characteristics in the Raman spectra of 4,4’-substituted biphenyl cations are that one or several bands, including the inter-ring C C stretching, are observed in the frequency range of 1200-1500 cm-l while no band of comparable intensity is observed in the frequency range below 700 cm-’ (Figure 6, f and g). They are very similar to the spectrum of the biphenyl anion (Figure 6h).13 The resonance Raman spectra of anisole- and halogenobenzene-montmorillonites, Figure6a-c, include the contribution from the dimeric cations (biphenyl type) as well as the monomeric cation radical. The resonance Raman spectra of
Soma et al.
742 The Journal of Physical Chemistry, Vol. 89, No. 5, 1985
Among the molecules which form cations, those s! own in the first column of the fatigue form cation radicals having the composition of the parent molecules, as exemplified by the case of p-dimetho~ybenzene~ and 4,4'-DMOBP: L
I
or
I I I
+
where X = OMe, C1, or Me and Y = OMe or OH. Molecules shown in the second column are found to form cation I radicals of the biphenyl type together with those having the composition of the parent molecules, the reaction being given in Figure 7. Ionization potentials of aromatic molecules grouped according (1). Molecules with low ionization potentials are found to readily to their adsorption behavior on transition-metal ion-exchanged montmorillonites. form a cation radical of the 4,4'-disubstituted biphenyl type. Toluene, exceptionally, does not form the dimer cation appreciably monomeric cation radicals contain some bands in the range below but undergoes other reactions. Reactions other than biphenyl-type 700 cm-l which are stronger than the bands in the 1200-1500-~m~~ dimerization also occur in the case of phenol. range, except for the anisole cation where a prominent ring C-O Benzene, biphenyl, and p-terphenyl, arranged in the third stretching band is observed at 1370 cm-'. Besides, the Raman column, polymerize to form the poly-p-phenylene cation as demspectra of adsorbed monosubstituted benzenes with 457.9-nm onstrated in the previous papers:',* excitation are always accompanied by a broad emission background while no significant background is observed in the spectrum of adsorbed 4,4-disubtituted biphenyls. The resonance Raman spectrum of phenol adsorbed on Cu2+or Fe3+-montmorillonite with 457.9-nm excitation agrees with the spectrum of 4,4'-dihydroxybiphenyl adsorbed on Cu2+montmorillonite. However, the color of montmorillonite darkens gradually with time of contact with phenol whereas the color of adsorbed 4,4'-dihydroxybiphenyl is unchanged. Apparently, reThus, the cation radicals or cations may remain stable when actions other than dimerization occur.16 Mortland et al. have the para positions of the benzene ring are occupied by stable obtained polymer products from a methanol extract of phenol substituents, or they undergo polymerization when the para adsorbed on Cu- or Fe-smectite." position is open. These reactions depend both on the ionization The absorption spectrum of adsorbed toluene (Figure 5e), potential of aromatic molecule and on the oxidizing power of the exhibiting a band around 450 nm with a shoulder as reported interlayer metal cation.6 Only metal ions with enough oxidizing earlier,3 indicates the formation of monomeric cation and the power can produce the cation radicals and the subsequent reaction. resonance Raman spectrum (Figure 6e) is also typical of a moThus Cr3+- and Caz+-montmorillonites are inert to the formation nomeric cation. However, the IR spectrum of adsorbed toluene of colored species. A very small amount of poly-p-phenylene cation indicates the formation of different adsorbed species on raising is formed on Pd2+-montmorillonite. The 4,4'-dichloro- or 4,4'the temperature. Pinnavaia obtained a brown waxy substance difluorobiphenyl cation was detected in the sample of monochlore from a methanol extract of toluene adsorbed on Fe3+-hectorite4 or monofluorobenzene adsorbed on Fe3+-montmorillonite. The and Thomas et al. reported the possibility of PhCH2PhCH3-type formation of poly-p-phenylene from adsorbed benzene proceeds products based on the mass spectrometric analysis of the reaction more rapidly on Fe3+- or Ru3+-montmorillonite than on Cu2+products of toluene-Cu-montmorillonite.ls The reason why montmorillonite. Therefore, the activity of Fe3+or Ru3+for radical toluene fails to form the biphenyl-type product and the definite formation is higher than that of Cuz+. This order corresponds identification of the product are uncertain. to that of the reduction potentials of metal ions. Reactions of Benzene Derivatives on Transition-Metal IonIn conclusion, information on the structure and behavior of Exchanged Montmorillonites. In Figure 7, the various aromatic adsorbed aromatic molecules on transition-metal ion-exchanged molecules studied are classified according to their characteristic montmorillonites has been obtained by the application of resonance behavior when adsorbed in the interlayer of transition-metal Raman spectroscopy. ion-exchanged montmorillonites. In the vertical direction molecules are plotted in order of their ionization potentials and in the Acknowledgment. The authors express their sincere gratitude horizontal direction they are grouped according to their reactions. to Professor Tadamasa Shida of Kyoto University for performing Molecules below and to the left side of the dotted lines are observed the measurement of absorption spectra of cation radicals in a freon to form cation radicals in the interlayer. Molecules to the right matrix and to Dr. Hitoshi Shindo and Dr. Jiro Hiraishi of National side of the vertical dotted line are not appreciably adsorbed, Chemical Laboratory for Industry, for affording them the use of probably because of their rigid and/or bulky structures. A cona Raman spectrophotometer with a dye laser. They are indebted siderable amount of hexafluorobenzene is adsorbed in the interto Dr. Hirochika Sakuragi of University of Tsukuba for his layer without forming a cation, presumably because of its high generous offer of 4,4'-dimethoxybiphenyl. ionization potential. Registry No. 4,4'-DMOBP, 2132-80-1; Cu, 7440-50-8; Fe, 7439-89-6; Ru, 7440- 18-8; montmorillonite, 1318-93-0; fluorobenzene, 462-06-6; anisole, 100-66-3; phenol, 108-95-2; benzonitrile, 100-47-0; toluene, (16) Soma, Y.;Soma, M., to be published. 108-88-3;4,4'-dihydroxybiphenyl, 92-88-6; chlorobenzene, 108-90-7. (17) Mortland, M. M.;Halloran, J. L. SoilSci. Soc. Am. J . 1976.40, 367. (M~O-OM~)
1 -
