APRIL, 1936
INDUSTRIAL AND ENGINEERING CHEMISTRY
Experimental Procedure
505
Benzylation
GRINDING AND ELECTROPHORESIS. Batches of air-dried commercial cornstarch were ground in a 4-gallon ball mill using 600 grams of starch to 8 kg. of pebbles and rotated at 45 to 55 r. p. m. for different lengths of time from 168 to 1848 hours. A portion of each batch was dispersed in water as follows: 150 grams of the ground sample were suspended in about 300 cc. of methanol to avoid lump formation, and the mixture was cautiously poured into 4 liters of boiling distilled water with vigorous stirring. This limpid dispersion was cooled then to room temperature and put in an electrophoretic cell, toluene was added, and 220 volts were applied (7,9 ) . When the supernatant liquor was clear and the sediment was tightly packed on the lower membrane, the liquid was siphoned off and the solids in it were determined by drying an aliquot at 100" to 105" C. The sediment was removed and L. McMASTER AND W. M. BRUNER again poured into 4 liters of boiling distilled water. When cool the process was repeated as before. A third dispersion into Washington University, St. Louis,Mo. boiling water was made, followed by electrophoresis. After the third portion of wash water was removed, the a-amylose was put into a tared dish and dried in the oven at 70" C. and weighed. DETERMINATION OF AMYLOSE FREEFROM RETROGRADED HE production of modern disinfectants MATERIAL (6). A suspension of the ground starch in 50 cc. of callsfor chemical compounds of high phenol methanol was poured cautiously with stirring into 300 cc. of boiling water. The boiling was continued for a few minutes to insure coefficients. It is therefore desirable to the breaking up of any lumps. The dispersion was then cooled prepare a t a reasonable cost such compounds as 0- and to room temperature and enough 12 per cent caustic solution p-benzylphenols which, when added to disinfectants, will was added to bring the alkali concentration to 2.5 per cent. increase their phenol coefficients. An improved method of The solution was cooled and concentrated hydrochloric acid was added in excess with constant stirring and cooling. The a-amypreparing these benzylphenols from benzyl chloride and an lose readily flocked out, and, after standing a short time, the excess of phenol has been developed. No use is made of precipitate was centrifuged off and washed repeatedly until the catalysts, organic solvents,l or reagents to separate the isowashings were neutral to methyl orange. The material was mers. There is also obtained a minimum yield of dibenzylthen dried in an oven at 70" C. and weighed. FRACTIONATION OF ,&AMYLOSE. The p-amylose fractions were phenols. The method is to melt the phenol, heat it to the obtained as the supernatant liquid from the electrophoretic desired temperature of benzylation, and stir vigorously with cells and were concentrated i n vacuo until they contained 5 to a mechanical stirrer while benzyl chloride is dropped slowly 6 per cent solids, and two volumes of methanol were added. into the reaction mixture. This procedure helps to minimize This mixture was allowed to stand 2 to 3 days, after which the supernatant liquid was removed and the precipitate was ground the formation of dibenzylphenols by preventing a local excess in methanol to a fine powder and then dried i n vacuo at 50" C. of benzyl chloride. Also, the principle of mass action is further The liquor which contained material not recipitated by the used by starting with an excess of phenol. methanol was concentrated i n vacuo at 40" to one-fifteenth of In the above reaction benzyl phenyl ether is first formed, its volume, and three volumes of methanol were added. The precipitate was allowed to settle and after several days was which, according to the well-known Claissen reaction, is removed and ground with methanol and dried i n vacuo at 50" C. rearranged to the benzylphenols under the conditions as stated. Ethyl alcohol as a precipitant will interfere with the alcoholNo benzyl phenyl ether could be identified in the undesired labile determination. A trace of electrolyte is necessary for by-products which are essentially the dibenzylphenols and a precipitation. ANALYSISOF CY-AMYLOSE FOR COMBINED FATTY ACIDS. The slight amount of tar. a-fractions were freed from extraneous fatty acids by triturating Benzylation was investigated at 125" C. using mole ratios under ethyl ether and dried in an oven at 60" to 70" C., and the (moles of phenol per mole of benzyl chloride) of 2 to 1, 4 to 1, amount of combined fatty acid was determined by the Rohrig etc., up to 10 to 1. Keeping the mole ratio constant at tube extraction method ( 1 ) after acid hydrolysis. This method was found to be more useful than the Taylor and Nelson technic 10 to 1, benzylation was tried a t 150' and 175" C. After for the small samples available here. Duplicate determinations benzylation was complete, the mixture was subjected to fracchecked within 1 per cent. tional distillation under diminished pressure and the benzylated products were thus separated without the use of solvents or reagents. This general method was followed in all cases. Literature Cited The yields of the monobenzylphenols when the tempera(1) Assoc. Official Agr. Chem., Methods of Analysis, p. 166 (1930). ture was kept a t 125" C. varied within wide limits. At the (2) Gore, IND. ENG.CREM.,20, 865 (1928). 10 to 1 mole ratio 89.5 per cent of the theoretical yield, based (3) Haworth, "Constitution of Sugars," London, Edward Arnold & Co., 1929; Hirst, Plant, and Wilkinson, J. Chem. SOC., 1932, on the weight of benzyl chloride used, was obtained, and 50 2375. per cent a t the 2 to 1 mole ratio. The yields of monobenzyl(4) Lintner, J.prakt. Chem. [N. S.],34,378 (1886). phenols when the mole ratio was kept a t 10 to 1 varied only (5) Meyer and Mark, Ber., 61,593 (1928); "Aufbau der hochpolyslightly with the temperature, the maximum yield being meren organ. Naturstoff," Leipzig, 1930. (6) Sidgwick, "Electron Theory of Valency," pp. 73, 134, London, obtained when the temperature of benzylation was 150' C. Oxford University Press, 1929; "Some Physical Properties of In all cases the yields of o-benzylphenol were greater than the Covalent Link in Chemistry," p. 27, Cornel1 University those of p-benzylphenol. Likewise, the quantity of residue in Press, 1933. the dibenzylphenol fraction was very small. (7) Taylor and Beckmann, J. Am. Chem. SOC.,51, 294 (1929). (8) Taylor, Fletcher, and Adams, IXD.ENG.CHEM.,Anal. Ed., 7, The excess phenol, the o-benzylphenol, the p-benzylphenol, 321 (1935). and the dibenzylphenols could be efficiently separated by (9) Taylor and Iddles, IND. EKG.CHEM.,18,713 (1926). fractionation under diminished pressure, using a 40-inch (101.648, 1739 (1926). (10) Taylor and Lehrman, J. Am. Chem. SOC., cm.) heated Vigreux column and a reflux ratio of about 5 (11) Taylor and Morris, I h i d . , 57, 1070 (1935). (12) Taylor and Salzmann, I b i d . , 55, 264 (1933). or 6 to 1. The o-benzylphenol (recorded melting point, (13) Taylor and Sherman, I h i d . , 55, 258 (1933). 21' C. for this labile form) and the p-benzylphenol (recorded melting point 84" C.) were obtained nearly colorless and of
of
PHENOL
6
RECEIVED September 27, 1935. Part of the material for this report is taken from a dissertation submitted by J. C. Keresztesy t a the Pure Science Faculty, Columbia University, in partial fulfillment of the requirement f o r the degree of doctor of philosophy.
1 Kalle and Company [German Patent 346,384 (Deo. 31, 1921)l and Courtot [Compl. rend., 187, 661 (1928)] mention the benzylation of phenol without the presence of a solvent. No details are given.
INDUSTRIAL AND ENGINEERING CHEMISTRY
506
VOL. 28, NO. 4
with a crystal of the stable form. The 52' C. form on redistillation may revert to the 21 O C. form.
Experimental Procedure
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technical purity after one such fractionation. The dibenzylphenol fraction was transferred to a modified Claisen flask and distilled between 203" and 216" C. a t 2.5 mm. pressure. This yellow, slightly fluorescent, highly viscous, oily fraction consisted mainly of a mixture of 2,4- and 2,6-dibenzylphenols, in addition to a small amount of residue. No attempt was made to separate the isomers of this fraction. For further purification of the p-benzylphenol for analytical purposes, crystallization from carbon tetrachloride gives excellent results. The o-benzylphenol may be further purified by slightly cooling a warm gasoline solution and separating the two layers in a separatory funnel. Redistillation of the lower layer yields a product of high purity.
BENZYLATION. Using run No. 6 as a typical example, 1021 gams of phenol were heated in a 2-liter, round-bottom flask fitted with a reflux condenser, thermometer, separatory funnel, and mercury-sealed stirring device, at an average temperature of 150' C. over an electric heater. Then 125 cc. (137.5 grams) of benzyl chloride were allowed to drop into the mixture during 4 hours. The mixture was vigorously stirred mechanically. Stirring and heating at the same temperature were continued for one hour after all the benz 1 chloride had been added. This procedure was to assure compLtion of the reaction and to allow all of the hydrogen chloride t o escape out of the vent tube of the reflux condenser. FRACTIONATION. The flask containing the benzylated mixture was attached to a 40-inch (101.6-cm.) Vigreux column fitted with a capillary bubble tube, condenser, manometer, purifying train, and vacuum pump. Fractionation was then slowly carried out at 1 to 5 mm. pressure. A small intermediate fraction was removed between the 0- and p-benzylphenol fractions. The dibenzylphenol fraction with the residue was transferred to a 250-cc. modified Claissen flask and distilled over a range of 203" to 216' C., at 2.5 mm. pressure. There were obtained 106 grams of the o-benzylphenol and 80 grams of the p-benzylphenol. These figures correspond to 52.7 and 39.9 per cent, respectively, of the total theoretical yield of 201 grams of monobenzylphenob based on the number of grams of benzyl chloride used. In this run 6, 18 grams of the undesired fraction were obtained. Figure 1 shows how the boiling points of 0- and p-benzyl phenol vary at low pressures with the pressure'
Summary and Conclusions
The benzylation of Phenol With benzyl chloride under different conditions of temperature and mole ratio without the use of catalysts, solvents, Or reagents, and the separation of the benzylated products by fractionation under diminished pressure were investigated. The yields of O-benZylPhenol in all Cases exceeded the Yields of the para isomer. The yields of the undesired fraction, consisting mainly of the dibenzylphenols, together with a small amount of tar, were found to vary considerably with the temperature a t a constant mole ratio. For the following reasons a temperature of 150' C. and a mole ratio of 10 to 1 may be reTABLEI. EXPERIMENTAL RESULTS WHEN137.5 GRAMS BENZYL CHLORIDE garded m the Optimum conditions Of The reaction is completed 2 to 3 hours sooner WEREUSEDIN EACHRUN than a t 12.5' C.; the yield of the undesired fraction Temp. of Run BenzylaMole Yield of ' Yield of Undesired is a minimum and that of the monobenzylphenols No. tion Ratio Phenol o-Benzylphenol p-Benzylphenol Fractlon c. Grams Grams % Urams % Grams is a maximum. Increasing the mole ratio b e 1 125 10:1 1021 100 49.7 80 39.8 24 yond 10 to 1 would doubtless further decrease 2 126 8:1 818 90 44.7 78 38.8 31 the yield of the undesired fraction and like3 125 6:1 614 86 42.8 76 37.8 40 4 125 4:1 409 82 40.8 72 35.8 100 70 wise increase the yield of the monobenzylphenols, 5 125 2:l 204 65 32 3 35 17.7 6 150 1O:l 1021 106 52.7 80 39.9 18 b u t p r a c t i c a l considerations would probably 23 7 150 8:l 818 97 48.8 72 35.8 render such an increase undesirable. 8 150 6:l 614 83 41.3 65 32.3 30 9 175 1O:l 1021 88 43.7 68 34.4 15 The separation of the benzylated products was efficiently accomplished by slow fractionation in a 40-inch Vigreux column. In all cases the labile form of o-benzylphenol (prismAcknowledgment like crvstals) was formed. However. as Claisen2 found. the Grateful acknowledgment is made to the Monsanto Chemilabile ;om was spontaneously converted to the stable form cal Company for suggesting this research. (octahedrons of recorded melting point 52' c.)if it was seeded O
2
Ann., 442,210 (1925).
RECEIVEDDecember 27, 1935.
