Sept. 5, 1955
LARGEMEMBERED RINGAzo COMPOUNDS
which may have contained some phenylacetaldehyde (XIX), while from the later eluates, 394 mg. (56%) of cholestan-3one ( I X ) was isolated. Desulfurization of Spiro-( 5-phenyl-l,3-oxathiolane-2,3 'cholestane) (=).-A s a m d e (0.82 e . ) of this hemithioketal was desulfuiized on the same day-and under exactly the same conditions as described for its isomer XVII. The steam distillate again was divided into two equal portions; one of them, after treatment with 2,4-dinitrophenylhydrazine, led to 27 mg. (12%) of acetozhenone ( X X I ) 2,4-dinitrophenylhydrazone, m.p. 247-249 . The second portion was transformed into its 3,5-dinitrobenzoate yielding 87 mg. (35%) of phenylmethylcarbinol ( X X I I ) 3,5-dinitrobenzoate, m.p. 94-95", [ a I z 5f ~7 " (G 0.9).13 As pointed out in the discussion, this rotation could not be obtained reproducibly and in one run the product was found to be optically inactive. Chromatography of the non-volatile portion gave 0.409 g. (67%) of pure cholestan-3-one (1x1. Spiro-(5-diphenylmethyl-l,3-oxathiolane-2,3 '-cholestane ) (XXIII).--4 mixture of 10.0 g. each of cholestan-3-one ( I X ) , l,l-diphenyl-3-mercaptopropan-2-ol(IV), freshly fused zinc chloride and anhydrous sodium sulfate in 70 cc. of dioxane was shaken for 2 days and then allowed to stand a t room temperature for an additional day. Dilution with ether, washing with water and 10% sodium carbonate solution, drying and evaporation left a residue which on successive concentration of its acetone solution gave three crystalline fractions ( A , B a n d C). Fraction A (4.1 g., m.p. 173-180') was recrystallized several times from chloroform-methanol (2.93 g. (needles) to constant m.p. 193-194", [a]"D +60°). Anal. Calcd. for C~ZHBOOS: C, 82.30; H, 9.87. Found: C, 82.04; H, 9.94. Fraction B (3.3 g., m.p. 162-165") was recrystallize? three times from acetone; yield 1.67 g., m.p. 172-173 (needles), [ C T ] ~ ~-9.7". D Anal. Calcd. for C&~OOS: C, 82.30; H , 9.87. Found: C, 82.15; H , 9.83. Fraction C (3.6 g., m.p. 130-135') crystallizes as prisms from acetone; yield 1.22 g., m.p. 70-80' then resolidifying ~ and melting a t 152-153', [ a I z 5+2.8". Anal. Calcd. for CUHF,~OS:C, 82.30; H, 9.87. Found: C, 82.60; H, 10.17. The infrared spectra (nujol mulls) of all three isomers showed distinct differences in the fingerprint region.
[CONTRIBUTION FROM
THE
465 1
Desulfurization of Spiro-(5-diphenylmethyl-l,3-oxathiolane-2,3'-cholestane) (XXIII).-W-2 Raney nickel catalyst (20 g., 3 days old) was refluxed with stirring for 1 hour with 250 cc. of ethyl methyl ketone, 2.0 g. of isomer A (m.p. 193-194') of the hemithioketal X X I I I was added and refluxing was continued with stirring for 24 hours. When the reaction was carried out in acetone solution, up to 80% of the hemithioketal was recovered. The catalyst was filtered, the solvent was removed and the residue was chromatographed in 36 fractions over 30 g. of Merck acid-washed alumina. The first 23 fractions, eluted with petroleum ether, furnished 975 mg. (780/0)of cholestan3-OXle ( I X ) , m.p. 126-127", while from the petroleum etherbenzene (1: 1) eluates, 20 mg: (2%) of cholestan-36-01 (VIII), m.p. 138-139', was obtained. The last 6 fractions, eluted with benzene, were combined and treated in pyridine solution with 3,5-dinitrobenzoyl chloride in the usual fashion. Crystallization from hexane gave 676 mg. (52%) of needles of the 3,5-dinitrobenzoate of ( + ) I ,1-diphenylpropan-2-01 ( V ) , m.p. 154.5-155", [ a I z 5 -46.1' ~ ( c 1.4), unchanged after three recrystallizations ( [a)2 5 -46.8'). ~ Anal. Calcd. for CzzHlgNzOa: C, 65.02; H, 4.46. Found: C, 64.78; H , 4.36. A sample (400 mg.) of the 3,5-dinitrobenzoate was refluxed for 2 hours with 300 cc. of 5% methanolic potassium hydroxide and the ( +)1 ,l-diphenylpropan-2-01 was crystallized three times from pentane, the melting point changing only by 1'; prisms, m.p. 57.5-58', [ a ] z S+5.8' ~ (~2.1). Anal. Calcd. for Cl&l6O: C, 84.87; H , 7.60. Found: C, 84.92; H , 7.64. Desulfurization of 1.0 g. of isomer C (m.p. 152-153') of the hemithioketal X X I I I under precisely the same conditions yielded 80% of cholestm-3-one and 380 mg. (57%) of the 3,5-dinitrobenzoate of ( - )1,l-diphenylpropan-2-01 m.p. 154.5-155", [ a l Z s$44' ~ (c 1.7). Admixtute with the above antipode lowered the m.p. to 129-130 , corresponding to the melting point of the racemic derivative which had been prepared independently. Anal. Calcd. for CzzHl&Oe: C, 65.02; H , 4.46. Found: C, 65.25; H , 4.57. Saponification as described above followed by recrystallization from pentane yielded prisms of ( - )l,l-diphenylpropan-2-01, m.p. 57.5-58', [ a ] 2 6 -5.8" ~ (c 2.6). Anal. Calcd. for ClSHl60: C, 84.87; H , 7.60. Found: C, 84.56; H, 7.63. DETROIT,MICHIGAN
Cy),
DEPARTMENT OF CHEMISTRY, INSTITUTE OF POLYMER RESEARCH, POLYTECHSIC INSTITUTE OF BROOKLYN]
Azo Compounds. XV. Biradical Sources. The Synthesis and Decomposition of Large Membered Ring Azo Compounds' BY C. G. OVERBERGER AND MILTONLAP KIN^ RECEIVED MARCH28, 1955 The cyclic bis azo compounds VI (n = 8,lO) have been prepared and characterized. A study of the decomposition of V I , n = 8, in xylene a t 120' resulted in the isolation and characterization of VII, a twenty-membered carbon ring. From the rate data obtained, it is suggested that both azo linkages in VI, n = 8, do not decompose a t exactly the same rate. Decomposition of VI, % = 8, in styrene gave no polystyrene under conditions in which a similar radical derived from a linear azo compound produced polymer. Thus, it is clear that biradical propagation cannot take place even under these favorable conditions.
We have initiated a study of the properties of moderately active biradicals in solution. A principal difficulty encountered in such a study has been (1) Presented in part before the Polymer Division at the 126th hleeting of the American Chemical Society, New York, September 1217, 1954. This is the 15th in a series of papers concerned with the preparation and decomposition of azo compounds. For the 14th paper in this series, see C . G. Overberger and B. F. Marks, THISJOURNAL, 77, 4104 (1955). (2) This paper comprises a portion of a thesis presented by Mr. M. Lapkin in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Graduate School of the Polytechnic Institute of Brooklyn.
the availability of biradical sources. There are numerous examples in the literature of organic compounds which are reported to contain two unpaired electrons in the triplet state. For the most part, however, these are either of the very stable triphenylmethyl type or very unstable biradicals suggested as intermediates in gas phase decompositions. It is impossible in an article of this type to review adequately the background but a compilation of references seems pertinent. One of the first compounds reported which showed some
C. G . OVERBERGER A N D MILTON LAPKIS
4652
properties of a biradical, (p,p'-phenylene-bisdiphenylmethyl (named as a biradical, although it exists in quinoid form), was obtained by Thiele in 1904.3 Muller and co-workers4 in a series of papers demonstrated that stable biradicals exist in a number of cases (111) and that several of the compounds which previously had been thought to exist as biradicals were actually largely diamagneticb (I, TI). More recent work utilizing paramagnetic resonance techniques has suggested that compounds of type I and others may be paramagnetic to a very slight extent6 i.e.
GH!-c=(_L)=c-c,,H ~
II
-
a-naphthyl I1
1
-
CsH,
'c1
a-naphthyl
\ d CiHb 11111
c1/
Wittig and co-workers' reported the effect of ring size on association or ring formation of the stable triarylmethane type of biradical. They attributed the radical dissociation of the hexasubstituted ethanes to the space occupied by, and the electrochemical character of, the substituents, and suggested that in strained ring systems there should be forces which also tend to increase the carbon bond distances and lead to dissociation to give biradicals. They prepared materials of different chain lengths of structure IV, and showed that when n was 1 or 2 the material was unassociated and had the chemical properties of a radical source.
I\:
A substantial amount of work has been reported (3) J. Thiele and H . Balhorn, R c r . , 37, 1453 (1904). (4) (a) E. Muller and I. hluller-Rodloff, An~z.,5 1 7 , 134 (l!O>); (b) E. Muller and I. llullet-Rodloff, B e l , W B , 1276 (1935); :c! E. Muller a n d H . Neuhoff, ibid., 72B, 2063 (1939); id) E . Rluller and E. Tietz, ibid., 74, 807 (1041); (e) E. hluller and €1. Pfanz, ibid., 74, 1051 (1941); ( f ) 1075 (1941); ( g ) E. l l u l l e r and E. Herttl, Ann., 666, 157 (1944). (5) (a) A. E. Tschitschibahin, Be?., 4 0 , 1810 (1807); (5) G. Ix'ittig a n d W. Weiner, A n n . , 483, 144 (1930); ( c ) S. Allard, Cotnpt. vend., 199, 423 (1934); ( d ) W. Schlenk and 11. Brauns, Bel,., 48, 716 (1940); ( e ) E . Clar, i b i d . , 6 6 , 503 (1932); (f) A. Schonherg, 3 ' r a w . Pti:.adar SOC.,32, 514 (1930); ( 6 ) C. Diiftai5se and A , Etienne, Coln,Qt. r e n d . . 201, 280 (1935). (6) C . A . Hutchison, Jr., A . Kou,alsky, R. h. Pastor and G. W. Wheland, J. Chem. P h y s . , 20, 1485 (1952). (7) (a) G. Wittig and M. Leo, B c r . , 62B, 1405 (192Y); (b) 61B, 854 (1928); ( c ) G. Wittig and F. yon Lupin, ibid., 61B,1627 (1928).
VOl. 77
on the transitory formation of biradicals, largely in the gas phase.8 A more recent development is concerned with the possibility of biradical initiation and biradical propagation in vinyl polymerization. The possible existence of biradicals in a vinyl polymerization was first discussed from a theoretical viewpoint by a number of worker^.^ Recent work both theoretical and experimentallo has demonstrated the improbability of biradical propagation although the question of whether biradical initiation can occur has not been resolved. The results indicated self termination or transfer of the biradicals within a short period of time, although the question whether any small ring polymer was actually formed by biradical initiation with a catalyst has not been answered. In a recent paper by Russell and Tobolskylofconcerned with the photolysis in methyl methacrylate of a cyclic disulfide, 1,4,5oxadithiacycloheptane, as a source of biradicals, it was demonstrated that biradical propagation does not occur. From the ultraviolet spectrum of the solution, some indication was obtained that the biradical had reacted with a t least one monomer unit before recombination since a loss of disulfide concentration was noted. Recent workersll have reported the preparation of polymeric azo compounds11a and cyclic peroxidesl1bmc as catalysts for radical polymerization. However, no evidence to show whether polymerization did occur by biradical propagation is reported, or even whether the catalyst actually decomposed to give biradicals. Cyclic azo compounds which would decompose :it moderate temperatures to give biradicals seemed attractive for a number of reasons. The mechanism of decomposition of several types of linear azo compounds has been studied in detail by a number of i n ~ e s t i g a t o r s so ~ ~ that background material was available. The decompositions of azo compouiids are usually capable of careful kinetic analysis as well as convenient product analysis. I n particular, we desired a compound in which the competing reaction of cyclization would be minimized, that is a ring size which would be more difficult to form than conventional 5-, 6- or 7-membered rings. This would (8)(a) I.. S Kxasel, J . Citein. Uawn and K . F. Hunter, Tralis. C. E . H . Bawn m d 1%'. J . Duunin Bawn and J . Llilsted, ibid., 35, 889 (1939); (e) C. H . Bamford and 11. G. W. Norrish, J . Ckeirz. S i c , 1321 (1938); ( f ) 0. D. Saltmarsh a n d R . 0.\Y. Norrish, i b d . 4.5.5 (1935); ( g ) h l SLwarc, J . Polymer Sci , 6 , XI!) (lcJ.51) f!V ;a) C. D Hurd, I w f ,Euz Cheo.. 26, .iO ( l Y 3 4 ) ; !Ill 11 Dmtal and H . Mark, 7 ' ~ i i ~ i P s .n r i i d u y S N . 32, 34 ( I 9 3 t i ) ; ( C I P J . I''lcir?, Tins JOIJRNAL, 59, 241 (1437). (IO! 1.1) R. K . Haward T v u m . F a r a d a y Sac., 46, 204 (1!)50); ( h ) B. H. Z i m m and J. K. B r a g g , J . Polwnei. .S
