CATALYTIC ALKYLATION OF TETRALIN

COMMUNICATION 5. ALKYLATION OF TETRALIN BY PRIMARY ALCOHOLS CONTAINING

C 7 AND ABOVE

N. I . S h u l k t n , N. A. P o z d n y a k , a n d E. D, L u b u z h

N. D. Zelinskli Institute of Organic Chemistry, Academy of Sciences of the USSR Translated from Izvestlya Akademil Nauk SSSR, Otdelenie Khlmicheskikh Nauk, No. 6. pp. 1098-1102, June, 1961 Original article submitted June 30, 1960

Recently we showed that the alkylation of tetralin by nonanol-1 takes place in the liquid phase in the presence of zinc chloride at 195-200" and at atmospheric pressure [1]. Under. these conditions the yield of the nonyl-tetralin fraction boiling at 190-200" 19 ram) amounts to ~50% calculated on the tetralin and alcohol, and to ~ 70~ calculated on the tetralin that actually reacts. In the present work we studied the alkylatlon of tetralin by primary alcohols of normal structure: heptyl, decyl and dodecyl. The experiments were carried out under the conditions which we had previously found to be optimal.

/ \ , / ~ , ZnCK/\/K .,CH3 I I q / ) K , / j \(CH~)n_ICHa

The yields of heptyl, decyl and dodecyltetralins amounted to 49.5, 48.3 and 38.5% respectively, calculated on the alcohol, and to 49.5, 48.3 and 19.4% calculated on the tetralin used. The yields based on tetralin that actu- ally reacted amounted to ~ V0ok in all cases. In the present paper data are presented on the structure of the alkyl- tetralins prepared both in the present study, as well as in earlier ones [1, 2]. A method of determining the structure of alkyltetralins was described by us in a separate article [3].

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

A mixture of tetralin, alcohol and zinc chloride in molar ratios (0.5 M), was heated for five hours at 195". The reaction mixture was freed from zinc chloride, dried over calcium chloride, and distilled through a column with an effectiveness of 15 throetical plates. The alkene, tetralin and alky]tetralin fractions were separated. Results of typical exper fments are shown in Table I . The analysis of the alkene fractions was carried out by the aid of combination dis- persion spectra.* The composition of the alkyltetralin fractions was determined by infrared spectroscopy. The infra- red spectra were taken on an IKS-12 spectrophotometer with an NaC1 and LiF prism. In order to determine the posi- tion of the alkyl group, infrared spectra of the alkyltetralin fractions were taken in the 700-850 cm -I and 1600-2000 cm -I regions, since it is known that in these regions nonplanar deformation vibrations of the C - H bonds of the aro- matic ring and their overtones arc observed [4]. Spectra in the region of the C - H valence vibrations at 2800-3000 cm "I were taken in order to determine the structure of the alkyl group. The imeusity of the 2930 and 2960 cm "I bands of the corresponding unsymmetrical valence vibrations of the C - H bonds in the CH z and CH a groups were studied. It was shown previously [3, 5 ] that the extinction coefficient c z of the 2960 cm "I band increases in proportion to the number of CH s groups in alkanes, alkylbenzenes and alkyltetralins (I CH a group per ~ I 0 0 units). The extinc- tion coefficient e i of the 2930 cm "I band, beginning with the propyl radical, also shows a proportional relationsblp to the number of CH 2 groups. For the alkyltetralins e I = 73ni - 120 [3]. By means of this relationship, the total number of CH a groups n I in alkyltet~alfn can be determined, and thus also the number of CH 2 groups in the alkyl r ad i ca l

From the data shown in Table i it is evident that on alkylating tetralin by means of alcohols, the correspond- ing fractions of alkenes (I, V and XI) are separated, Analysis by means of combination dispersion spectra showed that fraction I, b. p. 90-95*, was a mixture consisting of heptene-1 and beptene-2, principally the trans-isomers,

* Raman Spectra.

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The decene fraction V. which boiled within the limits of 85-45 ~ (4.5 mm), consisted of decene-5 (trans-isomer) and a small quantity of decene-1. Analysis of fraction XI, b. p. 75-80 ~ (4.5 ram) showed that it consi;ted of a mixture of tetralin and dodecene with a double bond located in the middle of the moIecule. Fractions II. VI and X consisted basically of tetralin that had not reacted. The decreased index of refraction of fraction X is explained by the pres- ence of dodecene, since the latter has a boiling point close to that of tetralin. Infrared spectroscopic analysis and comparison of physical properties of the intermediate fraction VII only succeeded in establishing.the presence of a slgall quantity of decyl alcohol. Fraction XII corresponds with dodecyl alcohol, characterized by an infrared ab- sorption band at 3350 cm "z. The yield of the heptyltetralin fraction (IV) amounted to 49.5%; that of the decyltetra- 1in fractions (VIII and IX) to 48.3% and mat of the dodecyltetralin fractions (XIII and XIV) to 38.5% calculated on the alcohbl used. The yields of alkyltetralius, calculated on the amount of tetralin that reacted, amounted to ~ 70%. The infrared spectra of the alkyltetralin fractions showed bands at 725,810,830, 1610, 1750, 1850, 1885, 2000 em "I. These bands correspond with the spectrum of 1,2,4-trisubstituted benzene [6] and to the spectrum of 6-ethyltetralin [4], Consequently, the alkyltetralim we prepared had an alkyl group at position 6 in the aromatic ring:

/ \ S

The results of the determination of the number of CH z and CHs groups, according to the method we described pre- viously [3], are shown in Table 2. From the data in Table 2 it can be seen that heptyltetralin, obtained on alkylat- ing heptene-1 [2] and heptyt alcohol, has identical structure.

TABLE 1. Results of the Alkylation of Tetralin by Alcohols

Fraction I Prate 7 i~ ~ ~ No. IB.p. ~ [ in to m tfraction,g I '4

I II

tII IV

V VI

VII N;Ilt

IX

X XI

XII NIII XIV XV

I MRforco~esp. alkTlte~s

calculated found

90--95 200--204 125--t45 t45--150

aim

4

Alkyla~on by n-heptanol-!

t2 , t t,40t0 0,7080 27,2 t,5400 0,9695

5,0 t,48t5 - - 57,0 1,5t80 0,9233 74,91 74,51

35--45 ] 69--75

t03--t58 158--t60 t60~-t71

Alkylation by n-decyl

4,5 [ t6 , t t,42t0 4,5 ] 2t,0 t,5420 4,5 5,2 t,4825 4,5 35,5 1,5045 4,5 30,0 1,4975

alcohol

0,7405 0,970t 0,8824 0,9092 0,8972

88,75 88,75

88,43 87,50

Alkylation by n-dodecyl alcohol (moLar ratio of tetralin to alcohol, 2 : 1)

65--75 75--80

t00--t20 t84--t87 187--t97 203--2t5

4,5 4,5 4,5 4,5 4,5 4,5

45,0 t0 , t t ,3

t8,0 t4,5 6,t

1,5360 0,9690 t,4320 0,7640 -- t,4440 0,8292 -- !,5060 0,9053 98,00 1,5t00 0,911t 98,00 1,4500 Hydrocarbon separated

with m.p. 35 ~

98,86 98,40

In order to determine the structure of nonyltetralin, which we had prepared previously [1], the fraction boiling in the broad range 190-200 ~ (9 ram) was subjected to careful distillation in a vacuum at 3 mm. Two basic fractions were obtained: a) b. p. 152-153~ nZ~ 1.5080; d2~ 4 0.9048 and b) b. p. 153-155~ n~~ 1.5130 and d 2~ 0.9100.* C19H~0. Calculated MR 84.14, found MR 84.87 and 85.11. These fractions have ten CH~ groups and two CH s groups (see Table 2); consequently they correspond to alkyltetralins with an iso-structure.

/C C--C

\ / ' \ J N/N//

*-~M-Methyloctyltetralin and 6-ethylheptyltetralin have nZ~ 1.5079 and 1.8110, and dZ~ 4 0.9077 and 0.9112 respec-

tively [ 7].

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The values found for the molecular refraction of the deeyltetraltn (Table 1, fr. VIII and IX) and the dodecyltetralln fractions (Table 1, ft. XIII and XIV) correspond well with the calculated values. These fractious are apparently Iso- meric alkyltetrallns. This assumption Is confirmed by the data from the Infrared spectra (see Table 2). Thus, on alkylating tetraltn by primary alcohols and alkenes-1 under the conditions we used, 6-isoalkyltetralins of the follow- lng general formula are formed:

/ , \ / :% C/H(CH2)n, CHa

__. "N(CHz)n CH a N / N / /

where n t may be equal to zero, one or above: n z is the number of methylene groups in the longest part of the alkene chain from the double bond; n 1 + nz = n is equal to the number of methylene groups In the original alkene molecule or in the one that is formed.

TABLE 2.

Results of Studies of the Spectra of Alkyltetralins

Fraction No. Alkyltetrallns

n-Heptyltetraltn Heptyltetralln

IV Heptyltetralln

vi i i IX XIII XIV

Nonyltetraltn Nonyltetralin

Deeyltetralln Decyltetralln Dodecyltetraltn Dodecyltetralfn

Ct nt

625 10 470 8 480 8

60O 10 535 10

655 11 675 11 875 13 770 12.0

~2 i

95 214 2OO

207 202

210 186 190 252

n2

1 2 2

2 2

2 2 2 2.5

Remarks

C allbratton" Obtained from

alkylation of heptene- 1 [

Obtained from alkylation of

n-nonyl alcohol

The results obtained give reason to assume that the alkylatton of tetralin by alcohols proceeds as follows:

t. CHa (CH2)nCH2CH2OH - -H~ CHa (CH2)nCH=CH~

Furthermore, a partial lsomerlzatlon of the alkene-1 that is formed may occur:

2. CHa (CH~)nCH =CHo. - . CH.~ (CH,z)n_ICH=CHCH3 etc.

/ C H a

\ / \ / / \ / \ / /

/ \ . , / % -I- ~H3 (CH,,) n tCH~CHCHa

\ / \ /

Other isomeric alkenes alkylate tetralin analogously.

/CH,~CHa /\/\-c~

--' [ ~(CH2),r-tCt 1:~ \ / \ / f

From the data shown in Table 1 it can be seen that along with alkylatlon of tetraltn by alkenes, a dimeriza- tion of the latter occurs with the formation of parafflntc hydrocarbons, apparently due to an oversupply of hydrogen. Thus, a hydrocarbon of composition C~4H50' m. p. 35* was separated from fraction XV, b. p. 203-215" (4.5 ram). In

1016

the remaining fractions the presence of dlmers may be assumed on the basis of the somewhat lower values of the in- dex of refraction of the corresponding fractions. Thus~ In fraction I I I a hydrocarbon of C14 composition may be pres- ent and in fraction IX, one of C,z0 composition.

The combination dispersion spectra were taken by G. K. Gatvoronskaya. to whom the authors express their thanks.

SUMMARY

1. The possibility of alkylatlng tetralin by primary alcohols of normal structure and containing C7, Ct0 and C~ In the liquid phase with the formation of 6-alkyltetralins of branched structure was demonstrated.

2. The yields of isoheptyl-, isodecyl- and isododecyltetralins amount to 49.5, 48.3 and 38.5q~ respectively, based on the original alcohol, and to ~ 70% of theoretical based on the tetralin that reacts.

LITERATURE CITED

i. N. L Shuikln and N. A. Pozdnyak, Izv. AN SSSR, Otd. Khim. Nauk 1960, 1094.

2, N.I. Shuikin, N. A. Pozdnyak, and V. A. Shlyapochnikov, Izv. AN SSSR, Otd. Khim. Nauk 1960, 125.

3. N.I. Shuikin, V. A. Shlyapochnlkov, N. A. Pozdnyak, and B. L. Lebcdev, Izv. AN SSSR, Otd. Kblm. Nauk 1961, 466.

4. C.M. Staveley and J. C. Smith, J. Inst. Petrol. 42, 55 (1956). 5. Yu. P. Egorov, V. A. Shapochnikov, and A. D. Petrov, Zh. priM. khlmii 1_.44~ 617 (1959). 6. C~ W. Yong, R. R. Duvall~ and N. Wright, Anal~. Chem. 2._33,709 (1951). 7. N.I. Shulkin, B. L~ Lebedev, and N. A. Pozdnyak, Doklady Akad. Nauk SSSR 131,335 (1960).

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 all of this peri-

odical l i terature may well be avai lable in Eng l i sh translation. A complete list of the cover-to- cover English translations appears at the back of this issue.

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