3832
F. D. GREENE.S. L. MISROCK.IND J. R . WOLFE,JR.
posed to sunlight for four days (March). The yellowishbrown deposit formed was filtered off and recrystallized from benzene in orange crystals, m.p. about 228' dec. idark brown melt), yield 0.3 g. The compound gave green color with concentrated sulfuric acid. It was difficultly soluble in glacial acetic acid but went easily into sodium hydroxide solution (10%) and in sodium carbonate solution at room temperature (red color) and was recovered unchanged from the latter solution by acidification. v gave in alcoholic solution, a deep green color with ferric chloride, which on addition of small quantities of aqueous ammonia or aqueous sodium carbonate solution turned reddishbrown. V gave a deep red color with titanic chloride and V sublimes in vacuum. Anal. Calcd. for C13H003N: C, 68.7; H , 3.9; S,6.2; active H, 0.9 (for 2 H). Found: C, 68.8; H , 3.9; N , 6.1; active H, 1.1. Oxidation of V to Phthalic Anhydride.-Five-tenths gram of V, 0.3 g. of mercuric sulfate and 4 ml. of concentrated sulfuric acid were placed in a glass retort (100-ml. capacity). The mixture was then heated in a metal-bath for 10 minute: a t 250' (bath temperature), then for 50 minutes a t 300-310 (bath temperature), when colorless needles were observed on the colder part of the retort tube. The crystals were scratched out of the tube and sublimed to give the characteristic needles of phthalic anhydride (m.p. and mixed m.p. determination and positive fluorescein test). Action of Hydrochloric Acid on V.-One-tenth gram of 1' and 10 ml. of dilute hydrochloric acid (1 : 1) were refluxed for 15 minutes. The mixture was allowed to cool and made alkaline with sodium hydroxide in presence of ice, when no evolution of ammonia was observed (HCl test). Action of o-Phenylenediamine on V.-Fifteen-hundredths gram of V and 0.1 g. of o-phenylenediamine were dissolved in the necessary amount of glacial acetic acid a t 30" and maintained a t this temperature for a half-hour. The mixture then was poured into ice-cold water (800 ml.) and left to stand for one hour. The orange deposit formed \vas filtered off and proved to be V; the m.p. was undepressed on adinixture with an authentic specimen; both samples gave the same ferric chloride reaction (green), the same titanic chloride reaction (deep red), the same color with aqueous sodium carbonate solution and the same shape and color of crystals (from benzene). The same experiment was carried out a t BO" and similar results were obtained. 1,2-Diacetoxy-j-aceto4-cyanonaphthalene.-Trvo-tciitlis
gram of V and 6 ml. of acetic anhydride ryere refluxed for one hour, poured on ice and left overnight. The deposit formed was filtered off and recrystallized from methyl alcohol in almost colorless crystals, m.p. 160" (deep reddishbrown melt), yield almost quantitative, iiot soluble in sodium .~~~.~ ~~
[CONTRIBUTION PROM
THE
DEPARTMEST OF
VOl. 77
hydroxide solution (10%) but soluble in alcohol giviiig '1. yellowish solution. Anal. Calcd. for CliHllOoS: C , 63.fi; €1, 4.2; S , 1.3. Found: C, 65.6; H, 4.3; N. 4.7.
1,2-Dihydroxy-3-propiono4-cyanonaphthalene(\. rcplace COCH? by COC2Hj).-One gram of propionaldehydc and 1 g. of I in 30 ml. of benzene were exposed to sunlight for a fortnight (May-June). There \vas no deposit; tlie solution was concentrated under reduced pressure arid cooled in ice. The orange deposit formed was filtered off and recrystallized from benzene in orange crystals, m.p. 168", 1-ield 0.22 g . The substance gave a green color with concentrated sulfuric acid. Anal. Calcd. for ClaHllO,~N: C , 69.7; I$, 4.6; N , 5.8; mol. wt., 241. Found: C, 69.6; H , 4.9; X, 5.6; mol. wt. (Rast), 229. 1,2-Dihydroxy-4-cyanonaphthalenefrom 4-Cyano-l,2naphthoquinone.-Five-tenths gram of 4-cyano-1,Z-n;iphthoquinone was powdered and suspended in 5 mi. of alcohol. A saturated solution of sodium hydrosulfite ( Sa&Ol (room temperature) \vas added dropwise I\-i -4ddition was continued till the color became \!.hen a pale bronn deposit separated out. -4s of water was added and the mixture warmed till tlie solid dissolved; i t w a s filtered while hot arid left to cool. Tlie product that separated \\-as filtered and recr!-stallizcti from dilute alcohol in colorless crystals, m.p. 208" (yield almost quantitative), undepressed on admixture w i t h :in autlicritic syecimeu . I 3 1,2-Diacetoxy-4-cyanonaphthalene. - - ' h u - t e ~ i t l i ~grain of 1 ,~-tiili~-tirox!--~-c!-3nonapiithaleri~ aiid i3 inl. of acetic ;riih!.dride were refluxed for one hour, ;)mired oii ice : ~ i i dleft for a fe\v hours. Tlie product obtuined WA, triturated well, filtered off and recrystallized from methyl alcohol i l l colorlesi cr>-Ltais, in.;,. 152" (1-ieltl :rlmost quantitative). I t gave iio color with conceiitrated sulfuric acid arid wa\ insoluble i n sodium li!.droxide solution ( l O % ' l . .1niiZ Calcd. for C,,€I1104S:C, 66.9; 11, 1.1; T,3.2; acet1.l group, 32.0 (for 2 ) . Found: C , 67.0; IH, 4.2; S, 5.1; acetyl group, -31.8. Hydrolysis of 1,2-Diacetoxy-4-cyano~aphthalene.-Onetenth grain of l,Z-diacetoxy-4-cyanonaphthalene, 6 inl. of concentrated hydrochloric acid and 4 ml. of ethyl alcohol were refluxed for three hr. on sand-hath, cooled antl diluted with water. Tlie colorless crl-stals formed (J-ield 0.05 g. ) were filtered off and proved to be l,Z-dihydrosy-i-c?.anoriaphthalenc h!- m.1). ,tnd mixed m.p. determination.;. Both sample? gavc tlie s;t:rie reaction with ferric chloride (grccii color).
CAIRO,EGTPI.
~
CHEMIS.TRY, ?dAShACHUSE.lTS
IXSIYTVIE 01: ' r E C H N 5 ILOGY]
The Structure of Anthracene Photodimers BY FREDERICK D. GREENE, S. LESLIEMISROCE; AND
JAXES
K.WOLFE,JR.
RECEIVED FEBRUARY 7, 195g The products resulting from the irradiation by suniight of several !$-substituted anthracene derivatives (l"or111y1,carhoiiiethoxy, hydroxymethyl) have been shown to be dimers composed of t w o anthracene units bonded togcther a t the 9,Y'arid 10,10'-positions. The head-to-hcad structure I for these products has been established by the uiiamhiguour s!wthesis of a compound possessing structure I via the intramolecular cyclization of 9-anthroic anhydride.
Introduction chloro,' carboxy3), the ,"-position {methyl,4 carbThe conversion of anthracene and antllracene oxy3), the l,-l-positions (chloromethyl'), the 1 , ( I derivatives to higher melting conlpounds by the positioiis (chlorobroillo2) :ind the 0-1)ositioti i, carlx)ry,3 iiietllyl,6 etllyl,6 i o r i i i y l i :incI action of sunlight has been knowrl since 1g(j(j w h e t i Fritzsche isolated dialithrac-eiie from irradiatioil ,,' weilrrt Klitnl,,crrr, Be,,,, 4,, 8ys ( 1 9 1 & ) , of a benzeiie solutiori uf arithraceiie. 51a1iy other (4) L V 11. o r l l { i o r ~ i 'u,lcl 1-1 .A. Z I ~ ~ A ~ ~ ; chCllf. ~~ ~~ J. , , 2 2 , 152 photomerides have been reported, derived fro111 ' t w ' . (81 11. M e y e r a n d A. Eckert, MonC1fsh , 39, 211 (1018) anthracenes substituted at the ~-positioIl( m e t h y l , ? (1;) . I . Willemart, Corr~pf r e ~ i d . ,206, 99:3 (1937). (1) J . Fritzsche, J . p r o k l . C h e w . , 101,333 (1867). ( 2 ) 0 . Fischer and H. Ziegler, ibid., [2] 86, 289 (1912).
' 7 ) P. U. Bartlett antl 1'. 1). Greene, THIS J O U K N A L , 76, I O X S (1954).
July 20, 1955
THESTRUCTURE OF ANTHRACENEPHOTODIMERS
carbomethoxy’) . Compounds involving substitution a t both the 9- and 10-positions were unaffected by sunlighte6 The dimeric nature of these products has been established by e b u l l i o s c ~ p i c ~and ~ ~ ~cryoscopic ~ method^.^ The results of a detailed study of dianthracene by electron diffractionlo and crystal structure analysiss were consistent with a formulation of the dimer as a structure composed of two anthracene units bonded a t the 9,9’- and 10,lO’positions. The present paper provides chemical evidence establishing this structure for the dimers of several 9-substituted anthracenes. Discussion Preparation of the Dimers.-Exposure to sunlight of a solution of the colored monomers in an inert solvent resulted in the slow precipitation of colorless material. For a particular derivative, the dimerization proceeded with roughly equal facility in a variety of solvents (benzene, chloroform, acetic acid and ethanol) although considerable variation was noted in the ease of dimerization of the different compounds. The following sequence is in the order of increasing ease of dimerization : 9-hydroxymethyl, 9-formyl, 9-carbomethoxy, 9-anthroic anhydride.” The anhydride, as expected, was the most rapid (by virtue of its intramolecular character), The reactions initially were run in quartz flasks, but investigations with the 9-formyl compound showed that the reaction proceeded equally well in Pyrex or soft glass vessels, an observation that may be applicable to the other compounds in this series. All of the photomerides that have been investigated are colorless compounds of higher melting point and lower solubility in the common solvents than the corresponding monomers. At the melting point, these compounds are quantitatively dissociated to the monomers. Structure.-A strong indication of the structure of the irradiation products of 9-substituted anthracene derivatives is provided by the infrared absorption spectra. The 6.0 p conjugated carbonyl band of 9-anthraldehyde is shifted to 5.8 in the dimer, characteristic of an unconjugated carbonyl group. The 6.9 p band in the carbon-hydrogen bending region which is observed as a single band in the 9-formyl, 9-hydroxymethyl derivatives and in 9anthroic anhydride is replaced by two bands a t 6.78 and 6.88 p in the photomerides (possibly due to a change in the nature of the C-10 carbon hydrogen bond). The two bands a t 6.9 and 6.98 p in 9-methyl anthroate are replaced by three bands, a t 6.78, 6.88 and 6.98 p . These observations are suggestive of a structure similar to that proposed for dianthracene, namely, two monomeric units bonded together a t the 9,9‘- and 10,10’-positions. However, with 9-substituted dimers, two such ( 8 ) W. R. Orndorff and F. K. Cameron, A m . Chcm. J., 17, 658 (1895). (9) K. Elhs, J . P r a k f . Chcm., [2], 44, 467 (1891). (10) J. Hengstenberg and J. Palacios, Anales veal SOL. e s p a n . $s y g u i m ( M a d r i d ) , SO, 5 (1932). ( 1 1 ) C. Dufrdisse and M. Gerard, Bull. SOC. chim. France, 151 4 , 2053 (1937), have reported that chloroform and carbon disulfide inhibited the photodimerization of anthracene while ether promoted It
3853
structures are possible : a head-to-head structure, I, and a head-to-tail structure, 11.
n R = -CHO, -COOC,Hj, --CI-I20H In order to distinguish between I and 11, an unambiguous synthesis of a compound possessing structure I was undertaken. 9-Anthroic anhydride was prepared by the action of ketene on 9-anthroic acid and subsequent pyrolysis of the mixed anhydride. The infrared spectrum of 9-anthroic anhydride shows the two bands characteristic of a conjugated anhydride a t 5.6 and 5.8 p . Irradiation of a solution of the anhydride in chloroform converted the yellow anhydride into a colorless anhydride, 111, whose infrared absorption spectrum exhibited a small band a t 5.4 p , a strong band a t 5.6 p and a strong band a t 8.08 p , characteristic of a five-membered cyclic anhydride. Reduction of this compound by an ethereal solution of lithium aluminum hydride
I11
gave predominantly the monomeric 9-hydroxymethylanthracene, accompanied by a small amount (10% yield) of dimeric 9-hydroxymethylanthracene (bis-9-hydroxymethylanthracene (I, R = CH20H)).I2 That the material was formed by the direct reduction of the cyclic anhydride and not by the dimerization of 9-hydroxymethylanthracene was shown by a control experiment in which 9-hydroxymethylanthracene, subjected to the reduction conditions, was recovered in quantitative yield. Reduction of bis-9-anthraldehyde and bis-9-methyl anthroate with ethereal lithium aluminum hydride gave bis-9-hydroxymethylanthracene. The bis(12) The facile formation of 9-hydroxymethylanthracene upon treatment of the cyclic anhydride with lithium aluminum hydride is paralleled by the ready acid-catalyzed dissociation of bis-9-anthraldehyde and bis-9-methyl anthroate. We believe that these cleavages are due t o electrostatic repulsions, e.#.
H
HO CHO
CHO
/
\C@
H@
7’’
b@C-H
)Ll
