2620
SHIPP
The apparatus was constructed of Marinitc with a 2-in. wall thickness throughout. An internal fan assured even heat distribution and markedly decreased stabilization time. A 1-mv. full-scale recorder with Disc Integrator was used. Vaporization of injected material was accomplished with a preheater with variable temperature control. Retention data are shown in Table I.
TABLE I RETENTION TIMES FOR METHYL 0-ETHYL-D-GLUCOSIDES' Compound
Retention time, min.
Methyl 2,3-di-O-ethyl-~-glucoside, a: form 28 @ form 36 Methyl 2,6-di-0-ethyl-~-glucoside,a: form 44 @ form 48 Methyl 6-O-ethyl-~-glucoside 95 Methyl 3-O-ethyl-~-glucoside 106 Methyl 2-O-ethyl-~-glucoside 113 a Column temperature was 190'; helium pressure was 9 p.s.i.g.; 10-ft. diethylene glycol succinate (20y0) column on 40-60-mesh firebrick. Where required, paper chromatography was done in the descending manner, employing solvent systems and spray reagents described p r e v i o u ~ l y . ~ ~ ~ Vinyl Starches.-The preparation and analysis of vinyl starch has been described.2 The vinyl amylose used ( D . S. 1.0) was prepared from corn amylose isolated by the Schoch procedure and having an amylose content of approximately 9870 as indicated by iodine sorption.1° The vinyl amylopectin used ( D . S. 1.1) was prepared from Amioca powdered,Il an unmodified waxy maize starch with an amylopectin content greater than 9770. Hydrogenation of Vinyl Starch.-A solution of v nyl starch (1.0 g.) in absolute methanol (150 ml.) with 0.8 g. of 5% palladium-on-carbon catalyHtl2was hydrogenated for 70 hr. at 50" and 1800 p.s.i.g. The reaction mixture was centrifuged to remove the catalyst; evaporation of the solvent yielded 0.95 g. of product which showed no vinyl ether groups either by iodimetric or hydroxylamine hydrochloride analysis. The product, ethyl starch, was not further characterized. (8) E. L. Hirst, L. Hough, and J . K. N. Jones, J . Chem. Soc., 928 (1949). (9) R. W. Lenz and C. V. Holmberg, Anal. Chem.. 28, 7 (1956). (10) We are indebted t o D r . R. J. Dimler, Agricultural Research Service, C. 5. Department of Agriculture, Peoria, Ill., f o r the preparation of the corn amyloee. (1 1) American-Maize Products Co., Roby, Ind. (12) Englehard Industries, Inc., Newark, N. J .
VOL.29
Methanolysis of Ethyl Starch.-The material obtained by hydrogenation of vinyl starch was refluxed for 36 hr. in a mixture of absolute methanol ( 100 ml.) and concentrated hydrochloric acid ( 3 ml.). When cool, the reaction mixture was treated with Anion Resin CT-37513for 2 hr. a t room temperature with stirring, The resin was removed by filtration, and the filtrate was reduced under vacuum to a clear pale yellow sirup. Hydrolysis Procedure for Ethyl Starch or Methyl 0-Ethyl+glucosides.-A 1-10-mg. sample of ethyl starch or methyl 0ethyl-D-glucoside wm dissolved in 1.7 ml. of 72% aqueous sulfuric acid by adding the solid gradually to the acid while keeping the misture ice-cold. After 30 min. the clear solution was diluted with water to 16-ml. total volume and refluxed for 6 hr. When cool, the reaction mixture was neutralized with Anion Resin CT-375, and the filtrate was concentrated to approximately 1 ml. Preparation of Authentic Substances for Chromatographic Comparison. Methyl 2-O-Ethyla-~-glucopyranoside.-The synthesis and characterization of this compound which was in our possession has been described previously. a Methyl 3-O-Ethyl-~-glucopyranoside.-The method of Glen, et al.," was used to prepare 3-O-ethyl-~-glucose. The product, m.p. 136.5-137.5", [ a ] Z 4+26.0" ~ ( 5 min.) (water, c 2 ) , w w refluxed for 20 hr. with a solution of 370 anhydrous hydrogen chloride in absolute methanol. After treatment of the reaction mixture with Anion Resin CT-375 and evaporation of the solvent, a very pale yellow sirup was obtained which was not further purified or characterized. Methyl 6-O-Ethyl-~-glucopyranoside.-The method of Ohle and Tessmar's was used to prepare 6-0-ethyl-~-glucose. The product, m.p. 155.5-156.5", [ a : I z s ~+57" (water, c a ) , was converted to the glucoside as described above and was not further purified or characterized. Methyl 2,3-Di-O-ethyl-~-glucopyranoside.-The method of Croon and Flamm6 was used to prepare 2,3-di-O-ethyl-~-glucose. The product did not crystallize, but was homogeneous by paper D (water, c 2 ) . The prodchromatography; it had [ C X ] ~ ~+51.7" uct was converted to the glucoside as described above and was not further characterized. Methyl 2,6-Di-O-ethyl-~-glucopyranoside.-Themethod of Reeves16 was utilized in the preparation of 2,6-di-O-ethyl-~~ glucose. The p r o d ~ c t , ~m.p. ' 112.5-114.5", [ a l Z 44-54.9' (water, c 2), was converted to the glucoside as described above and was not further characterized. -
Eli Lilly and Co., Indianapolis, I n d . W. Glen, G. Myers, and G. G r a n t , J . Chem. Soc., 2568 (1951). H. Ohle and K. Tessmar. Be?., 71B,1843 (1938). R. E. Reeves, J . Am. Chem. Soc., 70, 259 (1948). Croon and Flamrnb report the following d a t a for this sugar: 90-92", 114-115O; [ a ] * ' ~ f56' (water, c 2). (13) (14) (15) (16) (17)
Reactions of a-Substituted Polynitrotoluenes.
I.
m.p.
Synthesis of
2,2',4,4',6,6'-Hexanitrostilbene K. G. SHIPP T h e Organic Chemistry Division, U . S. Naval Ordnance Laboratory, Silver Spring, Maryland Received March 4, 1964
2,2',4,4',6,6'-Hexanitrostilbene(1) has been prepared from 2,4,6-trinitrobenzyl chloride by reaction with alcoholic potassium hydroxide. The product melts a t 316", 105" higher than the melting point for a product reported to be hexanitrostilbene, obtained from the reaction of 2,4,6-trinitrobenzyl bromide with alcoholic potassium hydroxide. That the product reported here is indeed 1 has been confirmed by molecular weight determination, elemental analyses, and by an unambiguous independent synthesis. The lower melting product obtained previously was probably 2,2',4,4',6,6'-hexanitrobibenayl.
Reich, Wetter, and Widnier' reported a 40% yield of a crystalline product from the reaction of 2,4,6trinitrobenxyl bromide with alcohol potassium hydroxide. Upon recrystallization from nitrobenzene this product formed pale yellow needles melting a t 211", and was assumed to be 2,2',4,4',6,6'-hexanitrostilbene. When this procedure was repeated in these laboratories (1) S . Reich, 0. Wetter. and M. Widmer, Ber.. 46, 3055 (1912).
in an effort to obtain a sample of 1 for study in a series of polynitroaromatic compounds, the results obtained were a t variance with those reported by Reich. Xo product similar to that reported was obtained. With 2,4,6-trinitrobenxyl chloride as the substrate in the reaction with alcoholic potassium hydroxide, however, a scintillating crystalline precipitate formed. This product crystallized from nitrobenzene in beauti-
SEPTEMBEH , 1964
262 1
S Y S T H E S I S O F 2,2’,4,4’,6,6’-HEXANITROSTILBER’E
hydrogen according to the procedures of BlatLs An over-all yield of 4045%, with each step having a niinimu111 yield of 65y0, was obtained from the following sequence of reactions. ful pale yellow needles which nielted from 316 instead of 211” as reported for 1 by Reich. The melting point discrepancy iiiight conceivably be a typographical error, but no correction was found on searching errata reported in later issues of the journal. Jn addition to the difference in nielting point there was also a discrepancy in the solubility of the product in acetone. Reich reported ready solubility in acetone a t ordinary temperatures, but the product obtained in these laboratories was only slightly soluble in hot acetone That the product from 2,4,6-trinitrobenzyl chloride was a stilbene and not a bibenzyl derivative was shown by the infrared spectrum which exhibited a band at 9,j.j c i n - ’ (CH deformation in trans -C=C-). The measured value of the molecular weight, 448, was in excellent agreement with the calculated value, 450.3, and elemental analyses were also satisfactory. Furthermore, by analogy with other nitrobenzyl chlorides such as 4-nitrobenzyl chloride, and 2,4-dinitrobenzyl chloride13which are known t o form the corresponding stilbenes by reaction with alcoholic potassium hydroxide, 1 would be the expected product from the reaction of 2,4,&trinitrobenzyl chloride with alcoholic base. The above evidence pointed rather definitively to the structure 1 for the trinitrobenzyl chloride-alkali reaction product. However, owing to the apparent discrepancy between these and the previous results,’ it was felt that an authentic saniple of 1 should be prepared by a n unequivocal synthetic route. The direct nitration of stilbene was previously4 shown to yield 2,2’,4,4’,6-pentanitrostilbene and not hexanitrostilbene. Alniost as unsuccessful was the attempted condensation of trinitrobenzaldehyde with t~initrotoluene.~I n this instance only trace amounts of a product which proved to be identical with 1 were ohtained. Siniilarly, an oxidative coupling6 of trinitrotoluene afforded less than 10% of a product identical with 1. S o n e of these procedures were considered acceptable as a n unambiguous synthetic route to 1 because of the low yields obtained in each instance. The unequivocal synthetic route took advantage of the high yield condensation reaction of trinitrotoluene with ben~aldehyde.~“Since the 2,4,6-trinitrostilbene obtained could not be nitrated to the hexanitro derivative directly14an hydroxyl group, a +lI substituent, was introduced into the &position of the unnitrated ring to enhance the reactivity of its ortho-para positions in a postnitration reaction. The hydroxyl group was selected since, following nitration, it could be converted to the chloride7 which, in turn, could be “reduced” to (2) R . Walden and A . Kernbaum, B e r . , 23, 1959 (1890). ( 3 ) R . Escales, 7bid.. 37, 3599 (1904). (4) I’. Challenger and P. H. Clapham. J . Chem. Soc., 1612 (1948). (5) Trinitrotoluene and benzaldehyde or rnononitrobenaaldehydes undergo aldol-type condensation to form the corresponding stilbene8 in 50-90% yielde: ( a ) G . Bishop and 0. L. Brady. 7 b i d . . 121, 2367 (1922): ib) J . Thiele and R . Escales, Ber., 34, 2846 (1901); (e) F. Ullrnann and M. Cschwind. i h n d . , 41, 2294 (1908). 16) Conditions a e r e identical with those used in preparing 2,2’,4,4‘tetranitrvstilbene from 2,4-dinitrotoluene in 7 5 % yield: A . H. Green and . I . Baddiley. J . Chem. SOC..98, 1721 (1908). (7) 31. Warrrian and V. I . Siele. J . O w . Chem.. 26, 2997 (1961).
O C H O
+
Pi-CHs
piperidine benzene
HO -
oCH=CHPi
2
4
3
NaI MeCOEt HOAc
e NOa
PiCH=CHPi
1
Pi = OZN
NOl
Condensation of 2,4,6-trinitrotoluene with 3-hydroxybenzaldehyde proceeded well in benzene solution with piperidine as cat,alyst to give the 3-hydroxy-2’,4’,6’trinitrostilbene (2) in 90% crude yield. The crude product was nitrated to 3-hydroxy-2,2’,4,4’,6,6’-hexanitrostilbene (3) in 60-65% yield and the product from the nitration procedure was crystallized from acetonitrile prior t o the removal of the hydroxyl group. Removal of the hydroxyl group was achieved by modification of the procedures of Blatt8 for the reduction of picryl chloride to trinitrobenzene. I n order to apply this reduction procedure to the stilbene 3, it was converted to the chloride 4 by treating the pyridine salt with phosphorus o ~ y c h l o r i d e . ~The crude chloride 4, obtained in 95% yield, was reduced directly by heating the heterogeneous mixture of 4 and sodium iodide in refluxing methyl ethyl ketone containing glacial acetic acid. By analogy with the work of Blatt, it was assumed that chloride was replaced by iodide, which in turn was reduced by hydrogen formed in situ from sodium iodide and acetic acid, although the iodide intermediate was not isolated. The reduction reaction afforded in crude yield a light tan solid which was purified by recrystallization from nitrobenzene. This product had a melting point of 316”, which was not depressed on admixture with the product from the 2,4,6-trinitrobenzyl chloride-alkali reaction. Additionally, the two samples had superiniposable infrared spectra and X-ray powder diffraction patterns. Since the 316” product from the 2,4,6-trinitrobenzyl chloride-alkali reaction obtained in this work is, indeed, 1, the question of the structure of Reich’s’ 211” product from the 2,4,6-trinitrobenzyl bromide-alkali reaction remains to be answered. Rather than a typographical error in the journal, a more reasonable explanation is that this product was hexanitrobibenzyl, which has a melting point of 218-220” and is readily soluble in acetone a t ambient temperatures. The format’ion of hexanitrobibenzyl under Reich’s conditions is best explained by the presence of unreacted 2,4,6-trinitrotoluene in the sample of 2,4,6-trinitrobenzyl bromide. (8) ( a ) A . Blatt and E. W . Tristram, J . A m . Chem. S o c . , 74, 6273 (19.52): ( b ) A . H . B l a t t and Norma Gross, J . Org. Chem., 22, 1046 (1957). (9) W. Will [ B e ? . , 47, 712 (191411 reported 212O a s the melting point for 2,2,.4.4’,6.6’-hexanitrobibenayl.However, samples prepared in these laboratories melted a t 218-220O. ( I O ) T h e trinitrobenzyl bromide used in Reich’s work1 was prepared by the bromination of 2.4,6-trinitrotoluene. Since trinitrotoluene a n d t r i nitrobenayl bromide have similar solubilities in oreanir solvents and nut uidely differing melting points, contamination of the bromide b y trinitrotoluene could be expected.
SHIPP
2622
The mode of forniation of hexanitrobibenzyl in Reich's' reaction, as well as the reaction path for the forniation of 1 in the 2,4,6-trinitrobenzyl chloride-alkali reaction are currently under investigation and will be the subject of a forthcoming communication.
Experimental11,l 2 2,4,6-Trinitrobenzyl Bromide .-This compound was prepared by the bromination of 2,4,6-trinitrotoluene in the presence of magnesium carbonate in a sealed glass tube according to the procedure of Ganguly.13 The yield of recrystallized material, m.p. 65", M"as 62%. 2,4,6-Trinitrobenzyl Alcohol.-Hydrolysis of 2,4,6-t,rinitrobenzyl bromide by refluxing with water13 gave a 63% yield of the alcohol, m.p. 100". 2,4,6-Trinitrobenzyl Chloride.-Conversion of 2,4,6-trinitrobenzyl alcohol to the chloride was accomplished by its reaction with phosphorus pentachloride in dry chloroform.13 A 93% yield of the chloride, m.p. 85", was obtained. 3-Hydroxy-P',4',6'-trinitrostilbene(2).-To a mixture of I00 g. (0.44 mole) of 2,4,6-trinitrotoluene, 50 g. (0.41 mole) of 3hydroxybenzaldehyde, and 750 ml. of benzene in a 1-1. roundbottomed flask was added 5 ml. of piperidine and the resulting mixture was heated to reflux using a condenser connected through a D e a n a t a r k trap. The reaction mixture was an homogeneous solution a t reflux temperature, init,ially a light orange color which gradually deepened to dark brown during t,he heating period. After 4.5-5 hr. a t reflux, when nearly the theoretical volume of water had collected in the Dean-Stark trap, i.e., ca. 7 ml., heating was discontinued and the solution was cooled. The yellow crystalline product which formed was filtered, washed with benzene and then hexane, and dried. It weighed 135 g., Recrystalor 90% of the theoretical, and melted a t 156-158'. lized from methanol it formed bright yellow needles which melted a t 160". A n a l . Calcd. for C14H&80~:C, 50.76; H, 2.73; N, 12.68. Found: C, 51.11, 51.37; H,2.82,2.96; X , 12.99, 12.56. 3-Hydroxy-2,2',4,4',6,6'-hexanitrostilbene (3).-The addition of 100 g . of 2 to 100 ml. of 96% sulfuric acid in a 400-ml. beaker produced a dark green colored slurry. This slurry was chilled in an ice and water bath and 150 ml. of 307, oleum was added slowly with stirring, keeping the temperature of the mixture under 30". The resulting dark red-brown viscous solution was allowed to stand a t room temperature for 15 min., then heated to 85" on the steam bath and held a t that temperature for 1 hr. Aft,er cooling to room temperature this solution was added slowly, witah rapid *timing, during 45 min., to a mixture of 100 ml. of 70% nitric acid and 50 ml. of 96%, sulfuric acid a t 55-60" accompanied by the addition of 200 ml. of 707, nitric acid in 25-ml. portions, Initially the reaction mixture was an homogeneous red-brown solution but, after about 5 min. a crystalline product appeared in the mixture and t8hecolor lightened to a light brown. The mixture was stirred for 10-15 min. after the addition of the stilbene-sulfuric acid solution was completed and tJhen drowned in 2 1. of flaked ice and water. The product was filtered, washed with water, and dried. The light tan filter cake weighed 140 g. Recrystallization from 2.5 1. of acetonitrile, Celite, and Darco, yielded 87.5 g., 62% of theoretical, of fine colorless needles which melted a t 274-275". An additional 5 g. of product could be obtained by evaporating the acetonitrile filtrate to ca. 200 ml. m d chilling. The combined yield was 65.5%. d n a l . Calcd. for ClrHsXsOls:C, 36.06; H , 1.30; N: 18.03. Found: C,36.53,36.56; H, 1.60,1.59; N, 17.33,17.95. Pyridine Salt of J-Hydroxy-2,2',4,4',6,6'-hexanitrostilbene.A suspension of 25 g. of 3 in 250 ml. of methanol was placed in a 1-1. creased round-bottomed flask equipped with a mechanical stirrer and heated in a water bath a t 50". To this slurry was added 10 ml. of pyridine and the mixture was stirred rapidly for 1 hr. There was an immediate formation of a yellow solid product replacing the colorless hydroxystilbene. After cooling the mixture the product was filtered, washed with methanol, (1 1) Melting points are uncorrected. Microanalyses were performed b y Professor hl. H. .\Idridge, Department of Chemistry, American University, m-ashington. D. C . (12) C a u t i o n ! M a n y of t h e compounds herein described are explosive in n a t u r e . Appropriate percautiona should b e taken in their handling. (13) I
