CONDENSATION PRODUCTS FROM BENZYL ALCOHOL

[CONTRIBUTION FROM THB

NOYES CHEMICAL LABORATORY, UNIVERSITY OF

ILLINOIS]

CONDENSATION PRODUCTS FROM BENZYL ALCOHOL. POLYBENZYLS R. L. SHRINER

AND

ARTHUR BERGER

Received DecembeT 11, 1940

The formation of a hydrocarbon analyzing for (C7H6)n by the action of boron fluoride, boron oxide, sulfuric acid, phosphorus pentoxide, or zinc chloride on benzyl alcohol or benzyl ether was first reported by Cannizzaro (1) in 1854. Compounds of apparently related structure were isolated by Nef (2) from the treatment of benzyl alcohol or various benzyl ethers or esters with sulfuric acid, phosphorus pentoxide, or aluminum chloride. Auger (3) found that sulfuric acid or aluminum chloride converted benzyl alcohol into a hydrocarbon, (C7H6)n, having a molecular weight corresponding to 16 to 18 units. By passing benzyl alcohol vapors at 300-360" over various dehydrating oxides, such as those of aluminum, titanium, and chromium, Sabatier and Mailhe (4),and later Mailhe and de Godon (5) using calcined alum at a lower temperature, prepared a yellow insoluble amorphous product also analyzing for (C7H6)n, which was apparently the same as a resinous substance previously reported (6, 7). From the treatment of benzyl alcohol or various benzyl ethers with stannic chloride, Zonew (8) obtained a polymeric hydrocarbon of similar analysis. By heating a mixture of benzyl alcohol and sulfuric acid trihydrate, Senderens (9) obtained a hydrocarbon (CTHs)., as did Meerwein and Pannwitz (10) using boron fluoride and the alcohol. Recently, Calcott, Tinker, and Weinmayr (11) reported the isolation of a hydrocarbon from the action of anhydrous hydrofluoric acid on benzyl alcohol. In the presence of numerous catalysts, benzyl chloride also forms a hydrocarbon (C7Ho), which apparently is similar to that obtained from the polymerization of benzyl alcohol. Various metals such as copper (7, 12), nickel (7, 12c), iron (13), aluminum (13), and zinc (13, 14) have all shown activity in polymerizing benzyl chloride. Both the zinc-copper (2, 15) and zinc-sodium (16) couples also react with the chloride to produce the (C7H& hydrocarbon. Numerous chlorides, including those of aluminum (2,3, 13, 17), iron (13, 17h, 18),tin (8, 17h), zinc (3, 13), barium (17g), and nickel (12b, 17g) have also been used to produce resinous hydrocarbons from benzyl chloride under various conditions. Self-condensation of benzyl chloride has also been effected by the action of iron pyrites (18) and of ferric oxide (19). 305

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R. L. SHRINER AND ARTHUR BERGER

Benzyl bromide (2, 15, 20) has been polymerized by similar catalysts. Benzyl fluoride (21), in the presence of either hydrofluoric or sulfuric acid, is readily transformed into a colorless glassy resin whose analysis is (C,Hs),. A product of apparently the same general composition can be produced from the condensation of benzene with formaldehyde in the presence of various dehydrating agents (22). Numerous other workers have reported the formation of hydrocarbon residues in reactions involving benzyl alcohol (9, 23) , benzyl ethers (23b, 24), benzyl chloride (12b, 23a, 25), or benzyl mercaptan (2G). All these previous investigations have shown that benzyl alcohol and many of its derivatives do form polymeric substances but very little specific information is available concerning the structure and properties of these products. An examination of the methods of synthesis, and of the elementary formula of the polymeric material would appear to permit of the two possible structures (I) and (11). H -C-

I I

CeHs

I The evidence for each of these formulas is somewhat fragmentary. Both 0- and p-benzylbenzyl chloride (17g, 27) have been isolated in reactions involving benzyl chloride and a catalyst. Either of these compounds could be the first step in the formation of a polymer of type (I). In addition, anthracene has been formed in numerous reactions involving benzyl compounds (14, 17a, 24a, 24b, 28). The isolation of the benzylbenzyl chlorides and of anthracene would indicate the possibility that the benzene rings in the polymer chain are linked through methylene groups as in formula (I). However, stilbene (29) has also been isolated in a number of reactions of benzyl compounds a fact which lends some weight to formula (11). On treatment with aluminum chloride in a manner similar to that used on benzyl chloride in some of the polymerizations reported, stilbene is converted into a compound (C14H&, originally reported to be a stilbene octamer (30), but later shown to be a trimer (31). This stilbene trimer differs from the hydrocarbon polymer of like analysis formed from benzyl alcohol and its derivatives, in being readily decomposed and oxidized. Some phenanthrene is always found in addition to the stilbene trimer, although as far as is known phenanthrene has never been formed as a product in any of the reactions of benzyl compounds with themselves. This fact, coupled with the auxiliary one; namely, that stilbene has never

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been found in any of the reactions of benzyl compounds which also gave rise to the (C7H& polymer, would appear to eliminate stilbene as an intermediate in the formation of the hydrocarbon polymer. The synthesis of 1 2 , 3 ,4 5 ,6-hexaphenylcyclohexane from benzyl compounds has been reported by several investigators (4,5 , 6, 7, 11). This compound could conceivably be formed as a cyclic trimer of stilbene, or by the cyclization of 6 units of formula 11. In spite of the many references which have been made to 1 , 2 , 3 4,5,6-hexaphenylcyclohexanethe evidence presented in support of this formula has been very slight. Xone of the previous investigators has reported a molecular weight or even a melting point for any of the products so designated. Apparently the material has never been isolated in any save an amorphous form with an empirical analysis corresponding to (C7H6)n. The formula given has been based on the analysis of a nitration product. Mailhe (7) originally gave the analysis of this nitration product as (C7H6N0&, but later, in collaboration with Sabatier (4), the analysis for the nitro compound was given as (CeH4NOz)eCeH6. No molecular weight or melting point was given for this nitration product, which would make it appear that this compound was also obtained in an amorphous state. Bezzi (17i) has shown that by varying the method of nitration on the (C7H*), hydrocarbon, one can obtain a product containing either less or more than one nitro group per benzyl unit. Thus it would appear that evidence based entirely on nitration is none too reliable. Olivier and Wit (19), working on a similar polymerization problem, have concluded from their results that the supposition of Sabatier and Mailhe that they had hexaphenylcyclohexane is erroneous. Thus all of the evidence favoring formula I1 is apparently unreliable. Since the information now a t hand, taken in conjunction with what is now known of the phenol-formaldehyde resins, appears overwhelmingly to favor formula I, and since the work to be presented later in this paper gives added evidence favoring formula I, this formula will be used in the subsequent discussion. In the studies of the polybenzyl hydrocarbons reported to date, both liquid and amorphous solid materials have been formed. The solids have been for the most part red or yellow in color, while the variously colored liquids have usually shown a marked fluorescence. In certain cases highly insoluble products have been formed, while in other instances hydrocarbons soluble in benzene and carbon disulfide have been isolated. Especially for the benzyl alcohol resins, very little information is available pertinent to the experimental conditions to be used in the preparation of one or another of these resinous materials. In view of this fact, part of the earlier work has been repeated and extended. The first condensation product used in the present investigation was )

)

)

308


prepared by adding benzyl alcohol dropwise to a well-stirred, cooled solution of concentrated sulfuric acid. The polymer forms immediately as a salmon-red, stringy, solid mass which floats on the sulfuric acid. This mixture is poured on cracked ice immediately after all of the alcohol has been added. A very insoluble green resin is formed in a short time if the salmon-red polymer is not removed quickly from the concentrated acid solution. The red color is discharged partially from the condensation product as soon as it is added to the cracked ice, and on further standing in the dilute acid solution it usually becomes a light cream color. The condensation product is separated from the liquid by a combination of decanting, centrifuging, and filtering, depending on the rate of coagulation. After being collected on a filter, the condensation product is washed with water until the washings show only a slight cloudiness with barium chloride solution. The solid remaining is air dried and powdered. All attempts to crystallize this product were unsuccessful. Though it is soluble in chloroform, carbon tetrachloride, benzene, carbon disulfide, toluene, benzaldehyde, ethyl bromide, and mesitylene, evaporation of solutions in these solvents leaves the polymer residue as a gummy mass. Since the condensation product dissolves only partially in dioxane, a separation of the polymer was made based on differences in solubility in this solvent. The dioxane-soluble portion was purified by repeated precipitation of the dioxane solution with water. The white polymer thus produced had a melting point range of 85-100" and gave no qualitative test for sulfur. Numerous analyses of this dioxane-soluble polymer from different reactionmixtures showed that the product is not a hydrocarbon as was expected, but that there must be some oxygen still left in the compound. The analytical data indicate that the material is a polybenzyl alcohol of the general composition shown in formula 111.

C6H5 CH2 (C6H4 CH2),CeH4 CHz OH I11 The combustion analyses suggest that this product has a value of n equal to about 9 for its average composition. Molecular weight determinations by the ebullioscopic method in chloroform and in dioxane gave the average values 952 and 830, respectively. Molecular weights by the viscometer method in benzene solution, using the constant given for polybenzyl by gave the average value 1218. The calBezzi (17i), K , = 4.01 X culated value for formula 111, n = 9, is 1008. Molecular weight determinations by the ebullioscopic or cryoscopic methods yield number average molecular weights (M,) whereas the viscosity method gives weight average molecular weights (Mw). The two methods therefore measure different types of average molecular


309

weights and since the values differ from each other, the polymer is probably rather heterogeneous in regard to chain lengths. The dioxane-insoluble portion was purified by repeated washings with dioxane and water. The white product thus produced, with a melting point range of 65-90", also gave no test for sulfur. Analysis indicated it to be a hydrocarbon -(CeH4CH2)--,. While this might be a cyclic product, it is unlikely that such is the case, since the method of preparation was not of the high dilution type, and the formation of a good yield of a cyclic product would be entirely unprecedented. It is, of course, possible that the chain is terminated a t each end by a hydrogen atom. However, it appears more likely from analogy with the benzyl chloride polymers which contain no chlorine that the insoluble polybenzyl is terminated by the formation of a stilbene structure (IV), although the existence of the double bond could not be detected by chemical means. C B H S C H(~C ~ H I C H ~ ) ~ C ~ H ~ C H = C H C B H ~ ( C CeH5 H~C~H~)~CH~ IV Molecular weights of this dioxane-insoluble polymer by the ebullioscopic method in chloroform gave the average value 1687, and by the viscometer method, a higher value, 2116. These molecular weight values correspond to a chain length of 19 to 24 benzyl units. It appeared that the simplest method of determining whether the chain was linked through ortho, meta, or para positions was by means of an oxidation to the polyketone followed by an alkaline fusion and isolation of the phthalic acids formed.

v CeHsC02H -t CsH4(CO2H)2 In agreement with earlier reports by Nastukoff (22a) and Jacobson (17h) on polybenzyls prepared by other methods, the polybenzyl hydrocarbon showed a remarkable stability to oxidizing agents. Even boiling alkaline, neutral, and dilute acid solutions of potassium permanganate had no noticeable effect on the condensation product. Chromic acid in acetic acid solution at room temperature and selenium dioxide in boiling dioxane for forty-eight hours produced little oxidation. Hot chromic acid and potassium dichromate in sulfuric acid gave oxidation products which could not be purified. However, 1:4 nitric acid readily produced a golden-yellow compound softening between 160-165' which contained no nitrogen. Its analysis and subsequent alkaline fusion products indicate that it is a polyketone (V), which may, from analogy with polybenzyl, be called polybenzoyl. This polyketone is soluble in chloroform, nitro-

310


benzene, benzyl alcohol, dioxane, and pyridine; slightly soluble in ethanol, Cellosolve, and Carbitol; insoluble in carbon tetrachloride, acetone, and aliphatic and aromatic hydrocarbons. It was insoluble in aqueous alkali indicating that no carboxyl group was a t the end of the chain. The average molecular weight of polybenzoyl by the ebullioscopic method in dioxane was found to be 890 and by the cryoscopic method in benzophenone was 1070, which indicates 9 or 10 benzoyl units. It also shows that some degradation had occurred during the oxidation. Fusion of the polyketone (V) with a mixture of sodium and potassium hydroxides a t 260” for twenty-four hours produced a mixture of benzoic acid and two of the phthalic acids. The acids were isolated by direct precipitation from the acidified fusion mixture and through an ether extraction on the acidified solution. Since benzoic and o-phthalic acids are fairly soluble in water, while both isophthalic and terephthalic acids are very insoluble in water, a separation of the mixed acids into two groups was easily made by means of this solvent. As a separation of the large excess of benzoic acid could not be made easily from the o-phthalic acid, the mixture of the two acids was purified and the amounts of each acid present determined by the neutral equivalent. No isophthalic acid was isolated in any fusion, so either extremely small amounts, or none of the meta compound was formed. In one experiment 0.5203 g. of terephthalic acid, 0.0899 g. of o-phthalic acid and about 5 g. of benzoic acid were isolated from the alkaline fusion of 20 g. of polyketone. The relative amounts of terephthalic and o-phthalic acid suggest a ratio of para to ortho linkage in the polymer of approximately 6 to 1. These results are necessarily quite inaccurate, not only because of the small amounts of dibasic acids obtained, but also because of differences in the chemical reactivity of the ortho and para isomers in the oxidation and alkaline fusion reactions. Nitration of polybenzyl has produced a variety of nitro derivatives depending on the solubility of the polybenzyl and the conditions used (4,7, 15, 16, 17b, 17c). In addition a mononitropolybenzyl has been prepared by the action of aluminum chloride on p-nitrobenzyl chloride (2d). Using fuming nitric acid Bezzi (17i) isolated a compound with 1 nitro group per benzyl unit, except for the end benzyl units, which presumably gained 2 nitro groups each as in formula VI. (The positions of the nitro groups on the rings are indeterminate.)

N O 2/-\-CH2 ”u‘

NOe [yo2 /-\-C& -

-

VI


311

When the condensation product from benzyl alcohol was treated with fuming nitric acid in the cold it produced a nitro derivative containing between 1 and 2 nitro groups per benzyl unit. Analysis of this nitro product for carbon, hydrogen, and nitrogen showed the presence of almost exactly 2 oxygen atoms for each nitrogen atom indicating that little or no oxidation had occurred during the nitration. The present work and other reports of the nitration of polybenzyl show that anywhere from a few nitro groups to a large number may be introduced into the polybenzyl molecule by varying the solubility of the condensation product and the nitrating conditions. Bromination of the condensation product with iron as a catalyst produced a bromo derivative containing between 1 and 2 bromine atoms per benzyl unit. By extracting the bromopolybenzyl with a small amount of chloroform, a product was separated whose analysis agreed closely with that of 1 bromine atom per benzyl unit. A product of similar analysis was obtained by Boeseken (20), and later by Jacobson (17h), from the pol-ymerization of p-bromobenzyl chloride. From the bromination of polybenzyl, Jacobson obtained a bromopolybenzyl containing 1 bromine atom for each pair of benzyl units. In order to determine the effect of other dehydrating acids on benzyl alcohol, it was treated with perchloric acid in the same manner as it had been with sulfuric acid. A pink colored Condensation product was formed when the benzyl alcohol was added dropwise to the perchloric acid. This material becomes white almost immediately when added to ice-water. It is quite soluble in dioxane, and may be purified from dioxane-water mixtures in the same manner as the condensation product from sulfuric acid. The perchloric acid condensation product softens below 60" and tends to darken very readily in air, even a t room temperature, so no satisfactory analysis or molecular weight could be made on this material. When benzyl alcohol was treated with fused boric acid a t 180" for about four hours and distilled immediately under reduced pressure an 86% yield of benzyl borate (32) resulted. The same reaction materials were heated for about twelve hours a t 180", cooled, shaken with excess alkali, and extracted with chloroform, dried, and vacuum distilled. Treatment of the distillate with ether gave a small amount of a solid which upon crystallization from benzene yielded colorless needles, m.p. 278-280". The crystals were soluble in benzene and chloroform, slightly soluble in ether, and insoluble in water, ethanol, and ligroin. Analysis of the material corresponded to (C,H,Jn, and molecular weight measurements in camphor gave the value 556, indicating that the crystalline material is one of the isomeric 1,2,3,4,5,6-hexaphenylcyclohexanes.

312


c€I

I

CsH6 EXPERIMENTAL

Preparation of the Condensation product. A 2-liter three-necked flask, containing 500 ml. of concentrated sulfuric acid, is fitted with an efficient mechanical stirrer, a thermometer reaching into the liquid, and a dropping-funnel containing about 75 ml. (0.72 mole) of benzyl alcohol. The acid is cooled to 0" in an ice-salt-bath, and the benzyl alcohol is added dropwise t o the well-stirred acid solution over about a thirty minute period, during which time the temperature of the acid mixture rises to about 20". With the addition of the first drop of the alcohol, a salmon-red, stringy solid which floats on the acid is formed. This color is retained if the acid solution is well stirred and the alcohol is added slowly enough to prevent any local excess of alcohol throughout the addition. If an excess of alcohol does accumulate a t any point i t will cause the formation of a greenish insoluble product. As soon as all of the benzyl alcohol has been added, the polymer-sulfuric acid mixture is poured with stirring into two 4-liter beakers, each containing about 2000 g. of cracked ice. The polymer is partially precipitated directly, its color usually a red-pink to a very faint pink a t first, gradually becoming cream colored to white after standing for some time. The water suspension is permitted to stand overnight or until the ice has melted, and one of the three following methods is used in separating the polymer from the liquid depending on the amount of separation which has taken place during this time. 1. If the condensation product has precipitated only slightly and remains essentially in a colloidal form, the dilute acid-polymer mixture is centrifuged, decanted, and washed with water until the polymer begins t o settle fairly rapidly. Then it is collected on a filter and washed with water until the washings give only a slight cloudiness with barium chloride solution. 2. If a considerable portion of the condensation product has settled to the bottom of the beakers, the upper layers are poured into another vessel and allowed to stand until a better separation of liquid and solid materials has occurred. The product which has settled out in the two beakers is combined and washed by nearly filling the beaker with water, stirring vigorously, and allowing the solid to separate out. The mixture is decanted and'the washing process is repeated until the solid begins to settle out of solution quite rapidly, which usually takes between five and fifteen such washings. The condensation product is now collected on a filter and washed with water until the washings give only a slight cloudiness with barium chloride solution. 3. If the condensation product has settled out of the dilute acid solution almost completely the supernatant liquid is removed by decantation and the solid collected on a filter and washed with water until the sulfate test is faint. The solid is now dried by sucking air through i t for twelve hours or more, and

POLYBENZYLS FROM BEKZYL ALCOHOL

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then i t is spread out and pressed on large sheets of blotting paper. During this partial drying process the polymer often reassumes a light pink color. On removal from the blotting paper the weight of the condensation product varies between approximately 60 and 100 g. (corresponding to a yield of 80-133% by weight depending on the extent of drying). For all of the work except the analysis and molecular weights this material, which will be referred to hereafter as crude, or simply polybenzyl, was used. This crude material starts t o soften at 65" and is completely liquid a t 77". Bromine in carbon tetrachloride, potassium permanganate, and bromine water are not decolorized by this product at room temperature. Purification of the condensation product. Dilute solutions of the polymer were prepared in chloroform, carbon tetrachloride, benzaldehyde, ethyl bromide, and dioxane. About 5 ml. of each of these solutions was added to about 50 ml. of each of the following solvents: 95% alcohol, absolute alcohol, water, ethyl ether, highboiling petroleum ether, low-boiling petroleum ether, acetone, methyl alcohol, acetic acid, and paraldehyde, except when the two solvents were not miscible. These mixtures were permitted t o stand overnight and then examined. Practically none of the mixtures save those of dioxane showed any evidence of the polymer having settled out as a solid, although an oil had separated out in a few cases. The dioxaneacetic acid solution contained a small precipitate of a light pink cream colored material. From the water-dioxane solution a small amount of a white material had precipitated and therefore in all succeeding purifications dioxane-water mixtures were used. Dilute solutions of the polymer were added dropwise with stirring to 40 to 50 volumes of water. The mixture was allowed to stand for twenty-four hours and collected on a filter if i t had separated sufficiently. Otherwise i t was centrifuged and washed in the centrifuge tube. By repeating the precipitation three times, a white product was isolated which was considered sufficiently pure for analysis. This material started to turn dark at about 80°, began to melt about 95", and was completely liquid a t 110'. The portion of the crude material which failed to dissolve in the dioxane was separated from the soluble portion by filtration and washed with considerable dioxane t o remove all of the soluble portion. The insoluble material remaining was quite gummy but came out as a white amorphous solid when placed in water. Soluble po2ymer: A n a l . Calc'd for C~H&H~(CBH&H.JI~OH: C, 91.62; H, 6.79 Mol. Wt. 1008. Found for three separate preparations: C, 91.51, 91.12, 91.68; H, 6.78, 6.87, 6.73. Molecular weight in chloroform: 963, 941. Molecular weight in dioxane: 843, 817. Molecular weight by viscometer; benzene solution, using K,,, = 4.01 X 1174, 1262. C, 93.29; H, 6.71. Mol. Wt. calc'd Insoluble polymer: A n a l . Calc'd for (C&).: for n = 19, 1710; n = 24, 2160. Found: C, 93.23; H, 6.67. Molecular weight in chloroform: 1630, 1743. Molecular weight by viscometer; benzene solution, using K,,, = 4.01 X 2198, 2033. Oxidation of polybenzyl with dilute nitric acid. T o 5 g. of polymer in a 1-liter round-bottomed flask was added a mixture of 100 ml. of concentrated nitric acid and 400 ml. of water and the combination was heated under reflux for forty-eight hours. After about a n hour a yellow-orange solid had separated from the nitric acid as a

314


hard crust, and this was broken up with a glass rod a few times during the reaction. In other runs, when 20-30 g. of polybenzyl was oxidized at once, after twelve hours the crust was broken up and then collected on a filter, ground, and then returned to the reaction flask with fresh 1:4 nitric acid. The reaction-mixture was cooled and the product collected on a filter. The precipitate, a yellow-orange solid, was repeatedly washed with water to remove the acid. On air-drying the material turned to a beautiful golden-yellow color. It gave no qualitative test for nitrogen. In a melting point tube i t began to darken slightly a t about 157" and softened completely between 160-165'. It was insoluble in hot alkali. A n a l . Calc'd for H ( C B H & O ) ~ ~ IC, I : 80.60; H, 4.06; Mol. Wt. 1042. Found: C, 80.64, 80.32; H, 4.55, 4.13. Molecular weight by boiling point method in dioxane: 876,903. Molecular weight by freezing point method in benzophenone: 1036, 1103. A l k a l i f u s i o n of polybenzoyl. T o 20 g. of polybenzoyl in a 200 ml. iron crucible was added a mixture of 25 g. of potassium hydroxide and 25 g. of sodium hydroxide. The mixture was heated to 260" for twenty-four hours. During this time the hard lumps which formed were broken up as well as possible with a metal rod, but mechanical stirring was impossible due to the size of the lumps formed. The mass was allowed to cool and dissolved in about a liter of water. A separation from insoluble material was made by filtration, the precipitate being washed with hot water until the washings were essentially colorless. At this stage in the process the solution was black in color. Hydrochloric acid was added and then 20 ml. excess of concentrated hydrochloric acid was added and the solution heated to boiling and filtered while hot. The filtrate was colorless and on standing for about twenty-four hours, terephthalic acid precipitated and was collected on a filter and crystallized from absolute ethanol. The remainder of the solution was evaporated down t o about a liter, and the organic materials removed by continuous ether extraction for seventytwo hours. Identification of acids formed from alkali fusion. The terephthalic acid weighed 0.52 g. and gave a neutral equivalent of 83.7 (theoretical 83.0). It failed t o melt or sublime in a melting point tube a t 340". When melted with phosphorus pentachloride i t gave a diacid chloride melting a t 80.5", which in mixture with pure terephthalyl chloride melted at 81". When treated with methanol a dimethyl ester formed, melting a t 139", which gave no depression in mixed melting point with a known sample of dimethyl terephthalate. The ether solution from the continuous extraction was evaporated t o dryness. The residue crystallized in colorless plates from water and weighed 5.2 g. It melted between 112" and 119"and a mixed melting point with benzoic acid gave a rise. The presence of o-phthalic acid was shown both by the formation of fluorescein and phenolphthalein. By sublimation, crystals were isolated melting at 130°, which gave no depression with pure phthalic anhydride, A neutral equivalent of very nearly 122 was obtained on the original material. By repeated crystallizations from water the phthalic acid was concentrated in the mother liquor, and finally 1.8 g. of the acid mixture was isolated by evaporating the filtrates using compressed air, airdrying, and then drying in a desiccator over magnesium perchlorate. This material gave a neutral equivalent of 119.3 on three trials. This neutral equivalent corresponds to 4.8y0o-phthalic acid and 95.2% benzoic acid or a total weight of 0.0899 g. of o-phthalic acid. Thus the ratio by weight of the dibasic acids isolated was 0.52 g. of terephthalic to 0.0899 g. of o-phthalic, corresponding t o a ratio of nearly 6 para to 1 ortho linkage in the original polybenzyl. Nitration of polybenzyl. T o 50 ml. of fuming nitric acid in a 100-ml. beaker cooled

POLYBENZYL8 FROM BENZYL ALCOHOL

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to 0" by an ice-salt-bath was added 2 g. of polybenzyl and the mixture was stirred for one minute and then poured on cracked ice. The light yellow nitration product was collected on a filter and washed with water to remove all of the acid. The nitro derivative softened a t 117" and was completely melted a t 132". I t gave none of the usual tests for a polynitro compound. A n a l . Calc'd for (C7HaN02),: C, 62.22; H , 3.73; N, 10.37. Calc'd for [C7H4(NO2)2ln:C, 46.61; H, 2.24; N, 15.56. Found: C, 52.58; H, 3.18; N, 12.96. Bromination of polybenzyl. In a 500-ml., round-bottomed flask fitted with an efficient reflux condenser bearing an outlet tube held above the surface of water was placed 10 g. of crude polybenzyl, 3 g. of iron powder, and 10 ml. of bromine dissolved in 200 ml. of chloroform. The mixture was refluxed overnight, or until hydrobromic acid stopped coming off. After cooling, the mixture was filtered t o remove iron, shaken with a solution of sodium bisulfite, and then the chloroform was evaporated. The product was collected on a filter and washed with alcohol. The brominated material started to soften a t 152"and was completely melted at 180'. A n a l . Calc'd for (CrHsBr),: C, 49.74; H, 2.98. Calc'd for (C?H4Br&: C, 33.90; H, 1.63. Mixed product, found: C, 39.16, 39.16; H, 2.29, 2.39. Soluble product, found: C, 49.49; H, 3.37. Pyrolysis of polybenzyl. Ten grams of polybenzyl was heated in a distilling flask up to 300". A small amount of a liquid distilled over up to 200°,but no visible change occurred later even when the temperature was raised to 300" and kept there for a few hours. The residue was a dark brown thermoplastic resin. The distillate was mainly water and a small amount of benzene. The latter was identified by extraction with ether, evaporation of the ether, and nitration of the residue with fuming nitric acid. When poured on ice and crystallized from alcohol the product melted a t 88" and a mixed melting point with m-dinitrobenzene gave no depression. Preparation of polybenzyl by use of perchloric acid. To 200 ml. of perchloric acid in a 400-ml. beaker cooled to 0" by an ice-salt-bath was added dropwise with stirring, 5-10 ml. of benzyl alcohol. The precipitate which formed immediately was a t first white and then a light pink. The mixture was poured into 600 g. of cracked ice with stirring. After the ice had melted the precipitate which had settled was decanted from the supernatant liquid, washed thoroughly with water, and then collected on a filter and air dried. This white amorphous material readily decomposed on standing in air, especially after drying, possibly due to occluded perchloric acid, and in a melting point tube was completely softened below 60". When dissolved in dioxane and reprecipitated by water, a soft material which hardened on standing in a vacuum desiccator was formed. When pulverized, this material softened between 60-65". I t was somewhat soluble in benzene but insoluble in ethanol, acetone, and ligroin. The crude polybenzyl prepared from the alcohol with perchloric acid was oxidized readily to a yellow product with 1:4 nitric acid on refluxing for twenty-four hours, just as was the polybenzyl from sulfuric acid. This oxidation product appeared t o decompose somewhat on standing in air. It softened between 100-115", and was soluble in dioxane and chloroform and insoluble in water, ethanol, ligroin, and carbon tetrachloride. A n a l . Calc'd for (C&O),: C, 79.22; H, 5.70. Found: C, 79.54; H, 5.59. Reaction of benzyl alcohol with boric oxide. To a 100-ml. beaker in an oil-bath heated to 180" was added 10-25 g. of fused boric acid and 50 ml. of benzyl alcohol. The mixture was covered with a watch glass and heated four to twelve hours.

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When the hot reaction-mixture after four hours time was distilled in vacuo, the temperature rose to 135' at 4 mm. pressure, and a few grams of benzyl ether distilled. Then the temperature rose t o 206" at the same pressure and 46 g. (86% of theoretical) of benzyl borate distilled. It gave a refractive index at 20" of 1.5544. The residue decomposed when the temperature was raised any higher. In one run, the reaction-mixture after twelve hours heating was treated with an excess of alkali to remove boric acid and anhydride, and then with alcohol and ether to remove benzyl ether. The residue was dried at 140" for twenty-four hours, but the remainder was a small amount of a dark brown very viscous liquid which could not be crystallized. A small amount of liquid distilled from this when heated in vacuo, together with a very small amount of solid which appeared t o be carried over with the liquid. When the reaction-mixture was heated for twelve hours, cooled and shaken with excess alkali, and extracted with chloroform, dried, and vacuum distilled, a small amount of a solid distilled over between 160-200" at 4 mm. together with a small amount of liquid. This solid was separated from the liquid by shaking with ether, in which the solid is insoluble, and filtering. The solid on crystallization from a small amount of benzene yielded needles, m.p. 276-280" (corr.). It i s soluble in benzene and chloroform, slightly soluble in ether, and insoluble in water, ethanol, and ligroin. Repeating this work in a sealed tube gave the same results. Anal. Calc'd for (C,H&: C, 93.29;H, 6.67. Found: C, 93.53;H, 6.74. Molecular weight, calc'd for 1,2,3,4,5,6-hexaphenylcyclohexane: 540. Molecular weight found in camphor: 556. SUMMARY

A polymeric condensation product was formed when benzyl alcohol was treated with cold concentrated sulfuric acid. This product was a mixture of at least two types of polymers. 1. A polybenzyl alcohol with analysis and molecular weight corresponding to the average composition: 2. A hydrocarbon whose analysis and molecular weight indicates a polybenzyl with the average composition :

The condensation product was oxidized by 1:4nitric acid to a polyketone. Cleavage of the latter by fusion with alkali yielded benzoic acid, o-phthalic acid, and terephthalic acid, which shows the presence of both ortho and para linkages in the original polymer. Nitration of the condensation product yielded a material containing between one and two nitro groups per benzyl unit. Bromination also produced a derivative containing one to two bromine atoms per benzyl unit. A condensation product of character similar to the polybenzyl from


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sulfuric acid was isolated when benzyl alcohol was treated with perchloric acid. Treatment of benzyl alcohol with fused boric oxide at 180”also produced polymeric condensation products. From this reaction there was isolated a small amount of a pure crystalline compound whose analysis and molecular weight indicate that it is one of the isomeric 1 2 , 3 ,4,5,6-hexaphenylcyclohexanes. ~

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CONDENSATION PRODUCTS FROM BENZYL ALCOHOL

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