C A T A L Y T I C D E H Y D R O C Y C L I Z A T I O N OF 2 - O C T Y L N A P H T H A L E N E

N. I. S h u i k i n , L. A. ~ r i v a n s k a y a , Y a n g A i - h s i , a n d L. P. R o m a n o v a

M. V. Lomonosov Moscow State University Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1469-1474, August, 1968 Original ar t ic le submitted July 9, 1962

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In the course of the investigation of the dehydrocycl izat ion of 2-hexylnaphthalene it was found that the process proceeds not only at a carbon atom of the naphthalene nucleus, but also at a carbon atom of the alkyl group i tself

with formation of 2-phenylnaphthalene [1]. An analogous react ion is observed for alkylbenzenes, which are converted under dehydrocycl iza t ion conditions into hydrocarbons of the biphenyl series [23. Our further observations showed that with increase in the number of carbon atoms in the alkyl group of the a lky lnaph tha lene cycl izat ion with formation of phenylnaphthalene homologs becomes sti l l more noteworthy. The cycl iza t ion products obtained from 2 - o c t y l - naphthalene (I) over an a lumina - chromium oxide catalyst (20% Cr203) at 450 ~ to an extent of about 5{Y/oconsisted of products of cyc l iza t ion at the naphthalene nucleus: phenanthrene (II) and a l i t t le anthracene (III). The remaining amount consisted of 11H-benzo[a_]fluorene (IV), l lH-benzo[b] f luorene (V), chrysene (VI?, and benz[a_]anthracene (VIB, probably formed from 2-o-e thy lphenylnaphtha lene (VIII), an intermediate product in the cycl iza t ion of 2- octylnaphthalene at a carbon atom of the a lkyl group. To confirm this view we special ly synthesized the 2 - ( 2 - m e t h y l -

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cyclohexenyl)- and 2-(2-ethylcyclohexenyl)-naphthalenes (IX) and (X) and subjected them to dehydrocyclization in presence of an alumina - chromium oxide catalyst at 450 ~ From the products of their catalytic transformations we succeeded in isolating llI-I-benzo[a]fluorene (IV) and 11H-benzo[b]fluorene (V) from (IX) and t t - m e t h y t - l l H - benzo[a]-fluorene (X!), l lH-benzo[a]f luorene (IV), and chrysene (VI) from (X). In addition, in the products of the transformations of 2-(2-ethyIcyclohexenyl)naphthalene we detected benz[a]anthracene spectroscopically.

P, enz[a]anthracene, found in the dehydrocyclization catalyzates from 2-octylnaDhthalene, could be formed both from 2-0-ethylphenylnaphtbalene (VIII) and also as a result of the dehydrocyclization of 1-butylanthracene (XII). We were unable to detect products of the cyclization of butytphenanthrene (XIII), i .e.,benzo[c]phenanthrene (XIV), ethylpyrene (XV), and pyrene itself. We cannot exclude the possibility that they are formed, but they are very difficult to find in such a complex mixture of condensed hydrocarbons as that obtained in the dehydrocycliza- tion of 2-octylnaphthalene. Moreover, these must be very small in amount because of the tow strength of the bond between the alkyI substituent and the quaternary carbon atom of phenantbrene under dehydrocyclization conditions [1]. Hende, the dehydrocyclization of 2-octylnaphthalene can be presented diagrammatically as follows:

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With increase in the length of the alkyl chain in the atkylnaphthatene the total yield of cyclization products falls and the cracking of the side chain becomes more marked. As a result of the dehydrocyclization of 2-octyt - naphthalene over an alumina - chromium oxide catalyst at 450 ~ with a space velocit 3, of 0.4 h "1 we obtained 37.6% of c3,clization products, whereas under analogous conditions from 2-butylnaphthalene we obtained 55.8~ of phenan- threne [3]. The main cracking products were methyl- , ethyl-, and propyl-naphthatenes. The naphthalene content

of the catalyzate was 1.3-2.5%.

EX PERI ME NT A L

2-Octylnaphthalene (I). This was synthesized by the reduction of heptyl 2-naphthyl ketone by a modification of Kizhner's method [4]. The ketone itself was prepared by reaction between naphthalene and octanoyl chIoride in presence of aluminum chloride in a nitrobenzene medium [5]. The yield was 75-78%; b.p. 243-245 ~ (5 ram); m.p. 54.5-55~ semicarbazone, m.p. t30-131 ~ The literature [6] gives: m.p. 56~ semicarbazone, m.p. 125 ~ 2-Octyl naphthalene had: b.p. 173-175 ~ (3 mm); n}~ 1.5513; d~ ~ 0.9360; MR 81.84. C18H~4. Calculated: MR 78.59. The exaltation of the molecular refraction was 3.25, which is in accord with data in the literature for 2-alt~ylnaphthalenes [5]. Ultraviolet spectrum (in methanol) [)Vma x, m/~ (log s)] : 275 (3.66), 304 (2.64), 319 (2.32). The literature[7] gives: b.p. 344* (760 mm); n}~ 1.5511; d240 0.9390.

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2- (2 - Methylcyclohexenyl)naphthalene (IX)___ 2 This was synthesized by r eaction between lithium, 2-bromonaphthalene [8], and 2-methylcyclohexan- one in a mixture of ether and benzene in a stream of nigrogen, and dehydration of the alcohol obtained under the action of potassium hydrogen sulfate [9]. After distillation )versodium we obtained a fraction of b.p. 156-172 ~ (5 ram); most of this came over at 163-t65 ~ (5 mm) and had n~ 1.6106; d~ ~ 1.0349. The product appeared to be a mixture of 2-(2 -methyl - l -cyc lohexen-1 -yl)- and 2- (5-methyl - l -cyc lohexen- l -y l ) -naphthalenes . The yield was 18.6% (on the 2-bromonaphthalene). Ultraviolet spectrum (in methanol) [kma x, mt~ ( log g)]: 225 (4.58), 245 (4.54), 275 (3.97), 285 (4.00), 295 (3.86).

2-(2-gthytcyclohexenyl)naphthalene (X). This was prepared analogously from 2-bromonaphthalene and 2-ethylcyclohexanone; yield about 20% ; b.p. 160-170 ~ (4 mm). n}~ 1.6108; d 4 1.0263; [)'max' m/~ (log 6)]: 240 (4.58), 277 (3.93), 285 (3.93).

Dehydrocyclization of 2-Octylnaphthalene (I). The procedure in the dehydrocyclization experiments and the analysis of the reaction products has been described previously [1]. The results are given in the table. Expt. 1 was carried out at 400 ~ at a space velocity of 0.1 h "l without the introduction of hydrogen from outside. Experiments 2 and 3 were carried out in a stream of hydrogen, which was passed at a rate of 2 Iiters/h at 450" with space velocities of 0,1 and 0.4 h "1.

By way of example we shall describe the results of the first experiment. From 18.6 g of 2-octylnaphthalene we obtained 11.7 g of catalyzate, of which 0.2 g (n~ 1. 3975) was condensed in a trap cooled with a mixture of acetone and solid carbon dioxide. This consisted of products of the cracking of the side chain in the alkylnaphthatene; they decolorized a 1% solution of potassium permanganate. We collected also 7.8 liters of gaseous products, which contained 81% of hydrogen and some cracking gases (see table). Vacuum fractionation of the catalyzate gave: Fraction I, 3.7 g (31.7%) boiling over the wide range of 80-140 ~ (3 ram); n}~ 1.6062; kmax~ m~: 275, 305, 318, 360; this consisted of unchanged octylnaphthalene (I) and its lower homologs together with a little chrysene (Vi), kma x, 360 mg [10]. Fraction II, 1.9 g (16.3%), m.p. 80-82"; this contained crude phenanthrene (II). Recrystallization from methanol raised its melting point to 99 .5q00 ~ Picrate, m.p. 142-143 ~ A mixture of the sub- s tance with pure phenanthrene and a mixture of their picrates melted without depression. The literature [1!] gives: phenanthrene, m.p. 99~ its picrate, m.p. 144 ~ Ultraviolet spectrum (in methanol) [kmax, mg (log e)]: 250 (4.88), 273 (4.18), 280 (4.02), 292 (4.69), 308 (2.51), 315 (2.53), 322 (2.59), 330 (2.60), 345 (2.58), 355 (2.50), 375 (2,47). The absorption maxima in the regions of 355 and 375 m/~ indicated the presence of 4-5% of anthracene (IlI) in the phe- nanthrene [10]. Fraction III, 5.6 g (47.7%), m.p. t40-142 ~ was subjected to chromatography on aIumina. After the removal of solvent we obtained: 1) 0.4 g of oily liquid products, n~ 1. 6220, probably consisting of alkylphenanthrenes or alkylanthracenes. Their analysis was not carried out because of insufficiency of material. 2) 1.1 g of crystalline products of m.p. 129-130 ~ raised to 203-204 ~ by repeated crystallization from a 7 : 3 mixture of alcohol and benzene. Ultra- violet spectrum (in methanol) [Xmax. m/l (log 8)]: 353 (4.6(1), 257 (4.57), 262 (4.73), 286 (4.04), 303 (4.0'/), 315 (4.00), 340 (3.16) , 357 (2.72), 375 (2.54) (Fig. 1). The character of the absorption spectrum coincided with the known spectrum o f 11H-benzo[b]fluorene (V) [10] with the exception of the absorption maxima in the regions of 357 and 375 mg, which indicated the presence of some anthracene (III). For llH-benzo[b]fluorene the literature [12] gives m.p. 204- 206 ~. 3) 1.45 g of crystals of m.p. 134-136 ~ from which by repeated crystalli-

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zation we isolated anthracene (III), m.p. 212-213". The li terature [13] gives re.p. 218". Ultraviolet spectrum [ k m a x, m~ (log s)] : 251 (5.01), 266 (4.39), 285 (3.66), 293 (3.62), 304 (3.64), 315 (3.65), 338 (3.43), 355 (3.52), 375 (3.53). The character of the spectrum indicates the presence of a l i t t le benzofluorene in the anthracene obtain-

ed (Fig. 2). 4) 1.75 g of crystals of m.p. 143-147". Here we were unable to isolate any homogeneous substances. The absorption spectrum (in benzene) had maxima at 292, 30:3, 318, 340, 360, 378, and 385 m#. It is probable that

this fraction contained a mixture of benz[a]anthracene (VII), }'max 292 and 385 mr, [10], benzofluorenes, and

chrysene (VI).

Apart from the above-descr ibed hydrocarbons, from the products of the cycl izat ion of 2-octylnaphthalene ob- tained in Expt. 3 we isolated l lH-benzo[a] f luorene (IV), m.p. 188.5-190". The l i terature [14] gives m.p. 183-184"; 188 ~ Ultraviolet spectrum [Xma x, m r (log s )]: 256 (4.58), 262 (4.7.3), 275 (4.25), 286 (4.32), 302 (4.00), 314 (3.98), 339 (3.37), 357 (2.92), 374 (2.12), 383 (2.21) (Fig. 3). The absorption maxima at 2'75, 286, 35"/, 3"/4, and 383 roll indicate that benz[a]anthracene (VII) is also present.

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aoa 400 ;~, m/.z Fig. 1. Ultraviolet spectrum of 11H- benzo[blfluorene obtained from octy l - naphthalene l--) and the spectrum of known 11H-benzo[b]fluorene [10] (- - - ).

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cene obtained from octylnaphthalene (--) and the spectrum of known anthracene

[103 (- - - ) .

. .Dehydrocyclization of 2-(2-Methylcyclohexenyl)naphthalene (IX). The experiments were carried out with a mixture of 2 - ( 2 - m e t h y l - 1 - c y c l o h e x e n - 1 - y l ) - and 2 - (5 -me thy l - l - c yc lohe xe n -1 -y l ) -na ph tha l e ne s . As a result of the ca ta ly t ic t reatment of 14.5 g of 2- (2-methylcyclohexenyl)naphthalene in presence of an a lumina - chromium oxide catalyst at 450 ~ at a space veloci ty of 0.15 h -1 we obtained 13.3 g of ca ta lyza te and 3.5 liters of gaseous prod- ucts. In the ca ta lyza te we identified 2-o- to ly lnaphtha lene from the mel t ing point of its complex with 1 ,3 ,5- t r ini t ro- benzene, m.p. 102-103 ~ [9]. In addit ion we isolated 11H-benzo[a]fluorene (IV), m.p. 189-190 ~ and 11H-benzo[b]- fluorene (VL m.p. 201-202 ~ Their ul t raviolet spectra were fully coincident with the spectra given in the l i te ra ture for these hydrocarbons [10]. The total y ie ld of benzofluorenes was 60-70% on the ca ta lyza te .

Dehydrocycl izat ion of 2-(2)gthylcyclohexenyl)naphthalene (X). From 12.2 g of the hydrocarbon, passed in presence of an alumina - chromium oxide catalyst at 455 ~ with a space veloci ty of 0.17 h -1, we obtained 9.6 g of ca ta lyza te and 3.8 liters of gaseous products, which contained %8% of ethane as well as hydrogen. From the ca t - a lyzate we isolated: l lH-benzo[a] f luorene (IV), m.p. 190-191~ 11-rnethyl-11H-benzo[a]f luorene (XI), m.p. 122- 123 ~ and re.p. of complex with 1 ,a ,a- t r in i t robenzene, 109-110 ~ The l i terature [15] gives: m.p. 120.5-122.5~ com- plex with trinitrobenzene, m.p. 109-110 ~ Ultraviolet spectrum (in i sooc tane) [Xma x, m~z (log s ) ] : 253 (4.'/5), 262(4.85), 27~/(4.15), 287(4.23), 300(4.14), 315(4.03), 340(3.12), 380 (1.59). The absorption maxima at

277, 287, and 380 mt~ indicate the presence of a l i t t le benz[a_]anthracene (VII). The total content of benzofluorenes in the ca ta lyzate was about 30~ Chrysene (VI), m.p. 249.5-250.5~ m.p. of complex with 1,3,5-trinirrobenzene,

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Fig. 3. Ultraviolet spectrum of 11H-benzo[a]fluorene obtained

from octylnaphthalene (--) and

the spectrum of known l l H - b e n - zo[a]fluorene [10] ( - - -).

189-190 ~ Its yield was 30~ The literature [16] gives m.p. 251~ complex

with trinitrobenzene, m.p. 188-194 ~ We estimated the content of 2-phenyl-

naphthalene (XVI) in the catalyzate from data on the analysis of the gaseous

products. 2-o-Ethylphenylnaphthalene (VIII) was not isolated in the indi-

vidual state.

The authors thank L. A. Kozitsyna, N. B. Kupletskaya, and other mem-

bers of the staff of the Laboratory for Physicochemical Methods of Analysis of the Chemistry Department of the Moscow State University, for the deter-

mination of ultraviolet spectra.

S U M M A R Y

1. The transformations of 2-octylnaphthalene, 2 - (2-methylcyc lo-

hexenyl)naphthalene, and 2-(2-ethylcyclohexenyl)naphthalene were inves-

tigated in presence of an alumina - chromium oxide catalyst at 450 ~

2. 2-Octylnaphthalene suffers dehydrocyclization both at the naphtha-

lene nucleus with formation of phenanthrene (mainly) and anthracene, and at a carbon atom of the alkyl group with formation of 11H-benzo[a]fluorene, 11H-benzo[b]fluorene, benz[a]antbracene, and chrysene.

3. The dehydrocyclization of 2-(2-methylcyclohexen.yl)naphthalene

gave l lH-benzo[a]f luorene and 11H-benzo[b]fluorene, and the dehydrocycli-

zation of 2-(2-ethylcyclohexenyl)naphthalene gave 11H-benzo[a]fluorene, 11H-benzo[b]fluorene, l l -methyl- l lH-benzo[a_]f luorene , benz[a]anthracene, and chrysene.

L I T E R A T U R E C I T E D

1. N.I . Shuikin, L. A. ~rivanskaya, N. L. Komissarova, and Yang Ai-hsi, Izv. AN SSSR. Otd. khim. n. 328 (1962).

2. I.L. Kotlyarevskii and M. S. Shvartsberg, Zh. obshch, khimii 29, 2639, 3255 (1959). 3. N. I . Shuikin, L. A. ~rivanskaya and Yang Ai-hsi, DokI. AN SSSR 133, 1125 (]960).

4. Huang-Minlon, J. Amer. Chem. Soe. 68, 2487 (1946).

5. A .S . Bailey, G. B. Picketing,and J. C. Smith, L Inst. Petrol. 35, 103 (1949). 6. Buu-Hoi and P. Gagniant, Bull. Soc. chim. France 12_, 307 (1945).

7. H. Luther and G. W~chter, Chem. Ber. 82, 161 (1949). 8. M.S. Newman and P. H. Wise, J. Amer. Chem. Soc. 63, 2847 (1941).

9, R.A. Friedel, M. Orchin and L. Reggel, J. Amer. Chem. Soc. 70, 199 (]948).

10. R.A. Friedel and M. Orchin, Ultraviolet Spectra of Aromatic Compounds. N, Y., (1951).

11. V. P,. Skvarchenko, Ling Weng-l ien and R. Ya. Levina, Zh. obshch, khimii 31, 383 (1961).

12. C .F . Koelseh, J. Amer. Chem. Soc. 55, 3887 (1933).

13. E. Clar, Aromatische Kohlenwasserstoffe, Berlin, 174 (1952). 14. J .W. Cook and C. L. Hewett, J. Chem. Soc. 374, 1737 (1934).

15. G.M. Badger, J. Chem. Soc. 535 (1941). 16. R. Weitenb6ck and H. Lieb, Monatsh 33, 549 (1912).

All abbreviations of periodicals in the above bibliography are letter-by-letter transliter- ations of the abbreviations as given in the original Russian journal. Some or al l o[ t h i s per i -

od i ca l l i t e r a t u r e m a y we l l b e a v a i l a b l e in E n g l i s h t rans la t ion . A complete list of the cover-to- cover English translations appears at the back of this issue.

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