B U L L E T I N D E L ' A C A D E M I E P O L O N A I S E D E S S C I E N C E S S é r i e des sciences chimiques Volume X X I , No, 7—8, 1973

ORGANIC CHEMISTRY

On the Structure of Dziewoński Hydrocarbons (Preliminary Communication)

by

T. URBAŃSKI and A. SELVA

Presented by T. URBAŃSKI on November 14, 1972

Summary. Samples of Dziewoński coloured hydrocarbons viz.: rhodacene, chalkacene and leu-kacene were examined in a mass spectrograph. It was found that their molecular weights do not agree with the suggested formulae but correspond to dekacyclene and dihydrodekacyclenes.

Karol Dziewoński and his colleagues published in 1920 a paper [1] describing the formation of deeply coloured hydrocarbons by pyrolysis of acenaphthene va­pours over iron or copper wire. Structures I—III were assigned to three main products of pyrolysis: rhodacene (I), chalkacene (II), and leukacene (III).

Dziewoński also postulated that rhodacene contains trivalent carbon atoms. The paper has been of considerable theoretical significance: it has shown that

an accumulation of condensed aromatic rings and hence of conjugated double bonds suffices to produce a deep coloration of the substances and should be cons­idered as a strong chromophore. This is now generally accepted.

However, doubts were cast on the structures suggested by Dziewoński. Clar [2] prepared terrylene ( C 3 0 H 1 6 ) which, according to the author, has a structure •dentical with that of rhodacene (I) or chalkacene (II) but possesses properties quite different from those of both hydrocarbons of Dziewoński. According to the same author, leukacene(III) might be a product of Diels—Alder addition of two moles of acenaphthylene to rhodacene.

At a later stage (about 1938—39) Dziewoński [3] became sceptical about the correctness of his own formulae and intended to resume experimental work to e'ucidate the structure with modern tools. The war-time conditions made impossible t° realize his plans before his untimely death in 1943.

One of the authors of the present paper undertook the task of finding out the structures of the Dziewoński hydrocarbons and as the first step he examined the 0 r 'ginal samples of compounds I—III, kindly offered to him by the late Professor J- Moszew.

[525]

526 T. Urbańsk i , A . Selva

The substances did not show high purity. This can easily be understood consi­dering 1 he epoch they were prepared when chromatography was practically unknown.

Mass spectrograph}!. Mass spectrographic examination has shown that hydro­carbons I and III give strong signals at m/e = 452, and II — at 450. These figures suggest that all three compounds belong to one family of dekacyclene (IV)—a trimer of acenaphthylene obtained by Dziewoński [4] by acting with sulphur on acenaphthene at 205—290/294°.

C 5 4 H 3 7 (M=680)

III

C36Hia(M=450)

I V

It appears from the mass spectra that rhodacene and leukacene are dihydro-genated dekacyclenes, and chalkacene is probably dekacyclene coloured by traces of rhodacene; indeed, thin-layer chromatography seems to confirm this.

Electron spin resonance. The existence of trivalent carbon atoms in I, i.e. the presence of free radicals, postulated by Dziewoński was now substantiated while examining ESR of the substances. Rhodacene (I) gave a very strong ESR signal-

On the Structure of Dziewoński Hydrocarbons 527

Much weaker were those of II and III. It is not excluded that the signals in the latter substances are produced by the presence of a certain amount of I in the samples.

N M R examination gave no useful information due to a very low solubility of the substances.

Experimental .

Mass spcctrography was carried out in a Hitachi—Pcrkin—Ellmer R M U 7 mass spectrometer. The temperatures were 200°, 250° and 260° for compounds I, II and III, respectively.

ESR was measured on an X-band apparatus having a modulation at 100 K H z , zl#max = 7.0 Oe. Further experiments will be carried out to obtain conclusive views on the structure of Dzie­

woński hydrocarbons.

The authors are much indebted to Dr. S. Benbenek for ESR measurements.

INSTITUTE O F O R G A N I C C H E M I S T R Y A N D T E C H N O L O G Y , T E C H N I C A L UNIVERSITY, K O S Z Y K O ­WA 75. 00-662 WARSAW

(INSTYTUT CHEMII I T E C H N O L O G I I O R G A N I C Z N E J , P O L I T E C H N I K A , WARSZAWA) ISTITUTO Dl C H I M I C A , POLITECNICO DI M I L A N O , 20133 M I L A N O

R E F E R E N C E S

[1] К. D z i e w o ń s k i , J. P o d g ó r s k a , Z . Lemberger , J. Suszko, Ber., 53, 2173 (1920). [2] E . C l a r , ibid., 65, 846 (1932); 81, 52, 63, 68 (1948); Aromatische Kohlenwasserstoffe,

2nd ed., Springer, Berlin, 1952; Polycyclic hydrocarbons, Vol. 2, Academic Press—Springer, London—New York—Berlin, 1964, p. 226.

[3] Private information from the late Professor J. Moszcw, former assistant to the late Pro­fessor K . Dziewoński.

[4] К . D z i e w o ń s k i , Ber., 36, 962 (1903).

Т. Урбаньски, А. Сэльва, О структуре углеводородов Дзевоньского (Предварительное сообщение) Содержание. При использовании массового спектрографа исследованы образцы цветных Углеводородов Дзевоньского, а именно: родацена (соединение I), халькацена (II) и лейко-чена (III). Констатировано, что их молекулярные весы не согласуются с предлагаемыми Формулами, но упомянутые углеводороды соответствуют дскациклену и дигидроде-кацикленам.