Jan., 1940
NOTES
227
I n other experiments the phosphorus tribromide was purified before use, but yields were increased only by a slight amount to 74.9%, of the theoretical. In an effort t o test the effect of temperature, the acetyl bromide was distilled from the reaction mixture a t room temperature under reduced pressure. The product was collected in a gas bottle immersed in a bath cooled with solid carbon dioxide. No change, however, was observed in the yield. I n all cases large amounts of hydrogen bromide were liberated so that the The Preparation of Acetyl Bromide* reaction probably does not proceed as indicated BY THEODORE M . BURTONWITH E D . F. DEGERING in the above equation. Acetyl bromide was prepared as early as 1863 It was found possible to prepare acetyl bromide by distilling it as formed from a mixture of glacial without the formation of hydrogen bromide by acetic acid, bromine and phosphorus. adding phosphorus tribromide slowly, with stirInvestigations have shown, however, that acetyl ring, to an excess of boiling acetic anhydride. bromide undergoes substitution with bromine to The boiling point dropped as acetyl bromide was form bromo-acetyl bromides with decrease in the formed and when the addition of phosphorus triyield of acetyl bromide. Further improvements bromide was completed, the acetyl bromide was designed to increase the yield of acetyl bromide distilled from the mixture and rectified as before. have also resulted in increased bromination in The yield was 81.7% of the theoretical. the nucleus.2 By using the readily prepared phosphorus triBy the elimination of free bromine i t was bromide, instead of free bromine with glacial thought possible to increase the yield of acetyl acetic acid, substitution reactions are avoided and bromide according to the reaction the yield of acetyl bromide can be increased to 3CH&OtH + PBrl ----f 3 C H s C O B r 4-P(0H)s about SOToof the theoretical. Phosphorus tribromide (b. p. 169-170' a t 740 CHEMICAL LABORATORY mm.) can be prepared readily in 99.5% yield by PURDUEUNIVERSITY AUGUST3 , 1939 WEST LAFAYETTE,INDIANA RECEIVED slowly adding dried bromine from a dropping funnel into a slight excess of freshly washed and dried red phosphorus placed in a round-bottomed Hydrogen Bonds Involving the C-H Link. 1X.I flask equipped with a mechanical stirrer and a re- Nitriles and Dinitriles a s Solvents for Hydrogen Containing Halogenated Methanes flux condenser. The acetyl bromide was prepared by adding BY M. J. COPLEY, G. F. ZELLKOEFERAND C. S. MARVEL slowly through the dropping funnel, with stirring, Nitriles should be capable of bonding with hya slight excess of 99.3ojC glacial acetic acid (3.075 drogen in halogenated methanes of the CHZXZ moles of CHaCOOH per mole of phosphorus triand CHX3 types and hence should be good solbromide) to the cold phosphorus tribromide. vents for these products. Work reported earlier' The mixture separated into two layers which were shows that valeronitrile and benzonitrile do disdistilled separately into a common receiver packed solve methylene chloride and monochlorodifluoroin ice. The crude acetyl bromide was rectified methane in excess of the amount calculated from in a modified Podbielniak column to produce a Raoult's law. It is interesting to find that the water-white fraction boiling from 73-76' a t 740 aliphatic dinitriles, succinonitrile and glutaronimm. The yield varied from 71.4 to 73.4y0 of the trile, dissolve less than the calculated amounts of theoretical. these two halogenated methanes. Adiponitrile *Presented before the Indiana Academy of Science at Terre Haute, Indiana, November, 1939. dissolves almost the exact calculated amount and (1) H. Gal, Ann., 129, 53 (1863); M .Hanriot, Ann. ckim. phrs., sebaconitrile takes up more than the calculated 151 17, 83 (1879). (2) H. Gal, Compl. rend., 66, 1258 (1863); F. Urech, Bey., 13, amount. These results are interesting when con1687 (1880); J. Volhard, Ann., 242, 144 (1887); C. Hell, Bet., 21, 1726 (1888); C. F. Ward, J . Chem. SOL, 123, 2207-2213 (1923); sidered with the boiling points of the dinitriles.
The acid amide was boiled under reflux with thirty parts of a 20% alcoholic solution of potassium hydroxide for three hours. The alcohol was replaced by water and acid evaporated, and the 4-methoxydibenzofuran-1-acetic was precipitated from the filtered solution. It was recrystallized from ethanol and appeared as colorless needles, m. p. 223-224". The yield was 90%. Anal. Calcd. for C1&20a: C , 7 0 . 2 8 ; H , 4.73. Found: C, 7 0 . 3 1 ; H, 4.43. UNIVERSITY, VIRGINIA RECEIVED NOVEMBER 21, 1939
H.B. Watson, ibid., 197, 2067-2082 (1825); Bernard Gwynn and Ed. F. Degering, Prsrr. I n d i o n ~Aood. Sci., 87 (lQ39).
(1) For the eighth communication ia thin i e r i u are TRISJ O V ~ N A L , 61, 8660 (1880).
