SYNTHESIS AND CATALYTIC DEHYDROCYCLIZATION

OF 2- AND 3-BUTYLPHENANTHRENES

(UDC 542.97 + 543.422)

N. I. Shuikin and N. L. Komissarova

N. D. Zelinskii Institute of Organic Chemistry, Academy of Sciences of the USSR Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. I, pp. 125-129, January, 1966 Original article submitted August 5, 1963

The reaction of catalytic dehydrocyelization, which was discovered in 1936, has been the subject of many investigations. It has been studied not only for aliphatic, but also for other hydrocarbons. Thus, alkylbenzenes with not less than four carbon atoms in the side chain are cyclized in presence of oxide cata- lysts with formation of naphthalene and its homologs [1]. The same compounds, though in lower yield, have been obtained from alkanes with not less than ten carbon atoms [2]. The subsequent systematic investiga- tion of the catalytic transformations of Cii--C20 and particularly Ci7--C20 alkanes led to the discovery of the polycyclization reaction with formation of polycondensed aromatic hydrocarbons [3-6]. In the further devel- opment of the investigations on catalytic dehydrocyclization papers appeared [7-9] on the catalytic transfor- mations of alkylnaphthalenes; the authors showed that the introduction of a second ring into the aromatic system leads to a considerable increase in the yield of cyclization products (up to 95%).

In the present work our object was the study of the catalytic transformations of a still more complex aromatic system -- alkylphenanthrenes. For this purpose we synthesized 2- and 3-butylphenanthrenes and studied their behavior over alumina-chromia and platinum catalysts. Over Cr2OJAl203 the reaction was conducted at 450 ~ at a space velocity for the feed of the original hydrocarbon of 0.2 h -1, and over platinized charcoal it was conducted at 350 ~ with a rate of feed of 0.i h -I (i.e., under the conditions which are optimal for the cyclization of alkylnaphthalenes). As a result of the cyclization of 2- and 3-butylphenanthrenes ever the alumina-chromia catalyst we obtained a catalyzate consisting of cyclization products to the extent of 90%. The remaining 10% was unchanged original hydrocarbon; This high yield of cyclization products was confirmed by the results of the analysis of the gaseous products, which consisted of almost 100% hydrogen. Traces of unsaturated compounds found in the gaseous products indicated that the cracking of the side chain of the butylphenanthrene occurred only to an extremely small extent.

Theoretically, tile cyclization of the isomeric butylphenanthrenes may go in two directions, i.e., in the catalyzate from 2-butylphenanthrene two products may be present,benz[a]anthracene (1) and chrysene (If),

C m C - - C - - C

(zl) (i]~}

and f rom the 3-butylphenanthrene ca ta lyzate we expected to obtain benz[a]anthracene {I) and benzo[c]phenan- threne (III). However , f rom all the ca ta lyza tes we only obtained chrysene in the pure s ta te . The format ion of chrysene in the dehydrocycl izat ion of 3-butylphenanthrene cannot be explained by the d i rec t cycl izat ion of

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TABLE i. Catalytic Dehydrocyclization of 2- and 3-Butylphenanthrenes

Hydrocarbon taken

2- Butylphenanthrene The same 3- Butylphenanthrene The same 2- Butylphenanthrene 3- Butylphenanthrene

Catalyst

Cr2OJA1203 The same

Pt/C The same

C ompos ition of catalyzate ,%

orig. hydro- carbon and

cracking products

10 8.5

11 9

100 100

cyclization products

9O 91.5 89 91

log 6

5

~ 7

I'~ J ~ lo

z I , , I I

250 J00 3Yg .~, , z ~

Fig. 1

8

% \

[ I I

2J0 300 3Y0 A, m l z

Fig. 2

Fig. 1. Ultraviolet absorption spec- t rum of chrysene obtained by the de- hydrocyclizat ion of butylphenanthrene. Fig. 2. Ultraviolet absorption spec- trum of the unpurified dehydrocycl i - zation catalyzate.

the latter. It is evident that under the given conditions 3-butylphenanthrene is i somer ized into the 2-der iv- ative, which then undergoes dehydrocyclizat ion with formation of chrysene. These resul ts are in accord with [10], in which the possibil i ty of the isomerizat ion of 3-alkylphenanthrenes into 2-alkylphenanthrenes was also noted.

Attempts to effect the dehydrocyclization over platinized charcoal at 350 ~ were unsuccessful: the eatalyzate consisted entirely of hydrocarbons of the phenanthrene series.

E X P E R I M E N T A L

The s tar t ing substances -- 2- and 3-butyrylphenanthrenes -- were prepared by the Fr iede l -Craf t s reaction by the acylation of phenanthrene with butyryl chloride in nitrobenzene in presence of aluminum chloride. The react ion mixture was decomposed in the usual way, nitrobenzene was distilled off, and the resul t ing mixture of ketones was vacuum-dist i l led; b.p. 260-290 ~ (10 ram); yield of mixture 50%. The mix- ture was treated with ether, when 3-butyrylphenanthrene went completely into solution, while 2-butyryl - phenanthrene remained undissolved. After recrys ta l l iza t ion from alcohol the ketones had the following proper t ies : 2-butyrylphenanthrene, m.p. 77 ~ semicarbazone, m.p. 182 ~ 3-butyrylphenanthrene, m.p. 50 ~ semicarbazone, m.p. 153 ~ The s t ruc tures of the ketones were proved by the presence of absorption bands at 1680 cm -1 charac te r i s t ic for a romat ic ketones and by their oxidation with sodium hypochlorite to the corresponding phenanthrenecarboxylic acids; 2-phenanthrenecarboxylic acid, m.p. 257 ~ 3-phenanthrene- earboxylic acid, m.p. 269 ~ (the l i tera ture [11] gives 258-260 ~ and 265-270 ~ respectively).

2- and 3-Butylphenanthrenes were prepared by the reduction of the corresponding ketones by the Kizhner method as modified by Huang-Minlon [12, 13]. The hydrocarbons were obtained in yields of about 85%. They had the following proper t ies : 2-butylphenanthrene, b.p. 196-198 ~ (4 ram), nD 2~ 1.6401, d4 ~~ 1.0374; 3-butylphenanthrene, b.p. 214-215 ~ (5 ram), nD2~ 1.6412, d420 1.0462.

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The alumina-chromia catalyst (20% Cr203) was prepared by the coprecipitation of aluminum and

chromium hydroxides from molar solutions of their nitrates with 20% ammonia solution; after being washed

and molded the catalyst was dried in a drying oven at 120 ~ and then roasted in the reaction tube in a stream

of air at 500 ~ For each experim ent the catalyst was regenerated by oxidation in a stream of air at 500-550 ~ for 14

to 16 h, after which its activity had been almost completely restored. The platinum catalyst (10% Pt) was prepared

by impregnating active birch charcoal with chloroplatinic acid and subsequent reduction with formaldehyde in an alkaline medium. For each experiment a fresh portion of catalyst was taken. The catalyst was given

a preliminary treatment with hydrogen for 4-6 h at 350 ~

The experiments were conducted in the usual flow-type apparatus at ordinary pressure in a weak

stream of hydrogen over the alumina-chromia catalyst at 450 ~ with a space velocity of 0.2 h -t or over the

the platinized charcoal at 350 ~ with a space velocity of 0.i h -I. For each experiment 15 g of the hydrocar-

bon was taken. The results of several experiments are presented in Table i.

The catalyzates obtained were analyzed with the aid of ultraviolet spectroscopy and by chromatography

on alumina. The relative weights of the sample taken for analysis and the adsorbent were 1 : I00. As sol- vent we used benzene, and elution of the fractions was conducted with benzene and methanol. The passage

of the fractions was followed by their ultraviolet fluorescence and refractive indices. The products were

identified on the basis of their properties and the results of spectral analysis. The gaseous products were

analyzed on a gas-adsorption chromatograph. In the experiments with 2- and 3-butylphenanthrenes on

Cr2OjAl203, the yields of the catalyzates amounted to 75-77%. The liquid part of the catalyzate consisted of unchanged butylphenanthrene, and the crystalline part (90%) consisted entirely of chrysene, which after

recrystallization from benzene melted at 248 ~ The literature [14] gives m.p. 250 ~ A mixture with known

chrysene melted without depression~ In Fig. i we give the ultraviolet absorption of pure chrysene (in alco-

hol), which is in good accord with data in the literature [14]. We also determined the ultraviolet absorption

spectrum of the unpurified catalyzate (Fig 2). Comparison of the two spectra appears to confirm the con-

clusion that the only product of the cyclization of butylphenanthrene is chrysene.

In the catalytic treatment of the butylphenanthrenes over platinized charcoal the yields of catalyzates

were 92-95%. In appearance and refractive index the catalyzates were close to the original butylphenan-

threnes, and their ultraviolet absorption spectra were almost identical to those of the original butylphenan-

thrones. In the gaseous products a small amount of Ci--C 4 hydrocarbons was detected; these were evi- dently formed by the cracking of the side chain of the butylphenanthrene.

All the spectra were determined by G. K. Gaivoronskaya, whom the authors thank.

CONCLUSIONS

1. An investigation was made of the catalytic dehydrocyclization of 2- and 3-butylphenanthrenes over

alumina-chromia and platinum catalysts.

2. The only cyclization product formed from 2- and 3-butylphenanthrenes over an alumina-chromia

catalyst at 450 ~ is chrysene; the reaction described can serve as a method for the synthesis of chrysene.

3. In presence of platinized charcoal at 350 ~ the dehydrocyclization of butylphenanthrenes does not go.

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

1. B . L . Moldavskii and G. D. Kamusher , DAN SSSR, 1, 343 (1936). 2. L . M . Rozenberg, DAN SSSR, 7_33, 719 (1950). 3. N . I . Shuikin and N. G. Bekauri, DAN SSSR, 126, 103 (1959). 4. N .G. Bekauri and N. I. Shuikin, Izv. AN SSSR, Otd. khim. n., 1961, 311. 5. N.G. Bekauri, N. I. Shuikin, and T. S. Shakarashvili , Izv. AN SSSR, Otd. khim. n., 1961, 318. 6. N . I . Shuikin, N. G. Bekanri, and A. I. Klimov, Authors ' cer t i f icate USSR No. 138084 (1960); Byull.

izobr. , No. 9 (1961). 7. N . I . Shuikin, L. A. ]~rivanskaya, and Yang Ai-hsi , DAN SSSR, 13___3_3, 1125 (1960). 8. N . I . Shuikin, L. A. ]~rivanskaya, N. L. Komissarova, and Yang Ai-hsi , Izv. AN SSSR, Otd. khim. n.,

1962, 327. 9. N . I . Shuikin, L. A. t~rivanskaya, and Yang Ai-hsi , Zh. obshch, khimii, 322, 823 (1962).

10. P . H . Gore, Chemical Reviews, 55,229 (1955).

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11. W . E . Baehmann and W. S. Struve, J. Amer. Chem. Soc., 5_88, 1659 (1936), 12. Huang-Minlon, J. Amer. Chemo Soc., 6.88, 2487 (1946). 13. A .S . Bailey, G. B. Pickering, and J. C. Smith, J. Inst. Pe t ro l . , 3___5_5, 103 (1943). 14. E. Clar , Aromatische Kohlenwasserstoffe , Berl in (1952).

All a b b r e v i a t i o n s of p e r i o d i c a l s in the above b i b l i o g r a p h y are l e t t e r -by - l e t t e r t r a n s l i t e r a - t i ons of the a b b r e v i a t i o n s as g i v e n in the o r ig ina l R u s s i a n j o u r n a l Some or a l l o f th is peri-

od ica l l i t e ra ture m a y w e l l be a v a i l a b l e in E n g l i s h t rans la t ion . A comple te l i s t of the cover - to -

cover E n g l i s h t r a n s l a t i o n s a ppea r s at the back of t h i s i s s u e .

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