2450 SUDBOROUGH AND THOMAS: THE ADDITION OFCCLI1.-The Addition of Bromine to UnsntzwatedCompounds. Part II.By JOHN JOSEPH SUDBOROUGH and JOHN THOMAS.IN continuation of the work already published (this vol., p. 715)we have examined the rate of addition of bromine to the followingacids : Cinnamylidene- and allocinnamylidene-acetic a.cid, sorbicacid, &phenyl-Aa-, -A&, and -A?-pentenoic acids, hydrosorbic acid,crotonic, angelic, tiglic, P-dimethylacrylic, and trimethylacrylic acid.The method of procedure was exactly the same as that used in theearlier work, and the carbon tetrachloride and bromine were purifiedin the same manner. A control experiment made with brassidicacid gave values for K varying from 3-0 to 6.9, as compared withthe previous values, 3.1 to 7.4.Although the new bromine andcarbon tetrachloride gave values for brassidic acid which were verysimilar t o the values obtained previously, it was found that whencinnamic acid was used, the values obtained were considerably lowerthan the earlier values, namely, 1-02 x 10-5 to 2.94 x 10-5, ascompared with 0.9 x We have not been able toascertain the reason for this difference, but we have been able toshow that the presence of moisture facilitates the addition ofbromine. This. is best shown in the case of the experiments withcrotonic acid :to 2.6 xK.7 '31 A lou5 t o 13.7 xDry carbon tetrachloride .... .. ............ 4-68 x to 6.16 x 10-6Moist ,, 9 9 .. .. . .. . . .. . . . .. BROMINE TO UNSATURATED COMPOIJNDS. PART 11.2451t (hours). n - x. l / t . r/n(n - 2).0'5 24 -8 4.16 x 10-31.0 23.95 3'511 -5 22-95 3.562'0 22'20 3-40The following table gives a list of ths values of K obtained forthe different acids a t 1 5 O :t (hours). (L - x. l / t . x/a(a - 2).0.5 24'8 4-16 x 10-31 -0 23.5 4 -311 5 22.0 4-512 *o 20 .a 4'92Olefine Acids.Maximum No. of l / t . ./.(a - x).Acids and formula. Series. time. titrations. Minimuni. Maximum.Crotonic, CHMe:CH*CO,H ...... n 189 hours 4 4.68 x 6.16 x l o d 6Angelic, CHMe:CMe*CO,H ...... a 145 .. 4 0'83 x loY4 1'9 x lo-'Tiglic, CHRle:CMe'CO,H ...... a 168 .. 4 1.3 k10-5 9-9 ~ 1 0 - 5fi-Dimethylacrylic, a 6 9 , 3 5.8 x10-3 7-0 xio-3CMe,:CMe'CO,H ............... a 8-5 .. 4 1.1 x10-2 2.2 x10-2CMr,:CHf!O,H ............... b 6 ..4 3.1 xlO-' 7'3 xTrinie t ti ylacrylic,6-Phenyl-A@-pentenoic, a 0.5 ,, 4 3-1 x10-1 3.7 x 1 0 - ICH,Ph*CH:CH*CH,*CO, ... b 0-5 .. 3 6'2 xlO-, 2-2 x10-'6-Phenyl-Ay-pentenoic, a 60 sees. 4 45.7 82.3CHPh:CH*CH2*CH,*C0,H.. . b 31 , . 4 35.5 60 *3Hydrosorbic, a 60 9 , 4 1.3 x102 3.3 x10'CH,Me'CH:CH'CH;CO,H ... b 20 ,, 4 2.4 x102 3.9 x102Diolefine Acids, with Conjugate Double Bonds.Sorbic, a 0.66 hours 3 1 ' 0 3 ~ 1 0 - ~ 6.8 ~ 1 0 Cinnainy lideneacetic a 1.0 ,, 3 2 * 2 1 ~ 1 0 - ~ 2 . 6 3 ~ 1 0 - ~a 1.05 y y 4 2 ' 5 6 ~ 1 0 - ~ 3.1 x ~ O - ~nlloCiiinaniylideneace~ic B 1-25 4 2'9 3.5 x10-,CHMe:CH*CH:CH*CO,H ... b 0'66 .. 4 1'1 X ~ O - ~ 12'2 X ~ O - ~CHPh:CH*CH:CH.CO,H ... b 4.5 .. 4 0 * 9 7 ~ 1 0 - ~ 1.3 x ~ O - ~.........The ap-unsaturated acid, 6-phenyl-Aa-pentenoic acid,CH,Ph CH,*CH : CH* CO,H,combines with bromine very slowly in the dark.Immediately aftermixing, the amount of bromine used up corresponded with 0.5 C.C.of the thiosulphate solution, and even after 190 hours the amountof thiosulphate required was the same. The acid thus combineswith bromine even less readily than does cinnamic acid. Thefollowing values were obtained for the two acids when the additionof bromine was allowed to take place in daylight; the two seriesof experiments were conducted side by side in order that the resultsshould be strictly comparable :Cinnamic Acid (a = 26.15).t (hours). n - x. l / t . x/a(a - z).0.5 16.7 4 *33 x 10-21 -0 12'7 4-051 5 8-15 5.632.0 5.5 7-12452 SUDROROUGH AND THOMAS: THE ADDITION OFThe results prove that in daylight bromine combines with the6-phenyl-Aa-pentenoic acid less readily than it does with cinnamicacid.The points to which we wish to draw attention in connexion withthe results tabulated above are:(1) The values confirm the generalisation drawn previously(p. 719), namely, that aP-unsaturated acids combine with brominefar less readily than the isomerides, in which the double linking isfurther removed from the carboxylic group.(2) The introduction of methyl substituents, attached to thecarbon atoms between which the olefine linking exists, facilitates theaddition of bromine to an appreciable extent.(3) When the acid contains conjugated olefine linkings, one ofwhich is in the a8-position with respect to the carboxylic group, theaddition of bromine takes place more readily than when theaS-ethylene linking alone is present.I n the examples we haveexamined, namely, sorbic, cinnamylideneacetic, and allo-cinnamylideneacetic acids, it is known that the two atoms ofbromine are added on in the a&positions, and the reaction is thusnot strictly comparable with the addition of bromine to cinnamicacid, where the bromine attaches itself at the aP-position.Preparation of the Acids.1. Cinnamyridenemalonic acid was prepared by the methoddescribed by Riiber (Ber., 1904, 37, 2274), with the exception thatthe mixture of equal weights of malonic acid, quinoline, andcinnamaldehyde were kept in a stoppered bottle for three weeksinstead of the two recommended by Riiber.The reduction of thesubstituted malonic acid was carried out according to Riiber’smethod, using pure mercury for the preparation of the amalgam,but the evolution of carbon dioxide and the formation of 6-phenyl-A.P-pentenoic acid, CH,Ph*CH:CH*CH,*C02H, was effected by asomewhat different method, as we had no method of obtaining apressure of 0.15 mm. (Ber., 1905, 38, 2746). The dibasic acid(25 grams) was heated in a sulphuric acid bat,h at 110-115° untilthe evolution of carbon dioxide had ceased, and the product, whichwas slightly coloured, was distilled under a pressure of 10-12 mm.,when the monobasic acid passed over at 176--182O, and solidifiedon cooling. The transformation of the By-acid into a mixture ofa& and 76-unsaturated acids was carried out according to Riiber’sdirections (Zoc.cit., p. 2747). The P-hydroxyphenylvaleric acid wasremoved by making use of its insolubility in hot carbon disulphide,and the oily acid removed by pressing the mixture of acid on aplate. The solid mass, consisting mainly of the 0sP- and y6-acidsBROMINE TO UNSATURATED COMPOUNDS. PART 11. 2453was dissolved in hot carbon disulphide, and, on cooling, crudeup-acid separated. From 150 grams of By-acid, 26 grams of crude&-acid were thus obtained, and after some six recrystallisationsthe acid was quite pure. To obtain the 76-acid, the carbon di-sulphide mother liquor was evaporated to dryness, and the acidtransformed into the sparingly soluble calcium salt under theconditions described by Riiber.The acid obtained from the calcium’salt still contained a@-acid, and this was removed by crystallisationfrom carbon disulphide and mechanically removing the characteristicplates of the y6-acid and crystallising from light petroleum, when11.5 grams of pure acid, melting a t 9l0, were obtained.Twenty-five gramsof sorbic acid were dissolved in sodium hydroxide solution, andthe whole made up to 300 C.C. with water. The solution was trans-ferred to a separating funnel, and placed in a bath at 30-35O.Rather more than the theoretical amount *of 3 per cent. sodiumamalgam was added in small amounts at a time, and the funnelwas shaken vigorously after each addition. The reduction pro-ceeded vigorously at the beginning, but slackened toward the end.The mercury was removed, the solution acidified with hydrochloricacid (1 : l), and extracted with ether. After removal of the ether,13 grams of hydrosorbic acid, boiling a t 103°/9-10 mm., wereobtained. When the distillation was continued, the temperaturerose rapidly, but did not become constant.3. Cinnamylideneacetic and allocinnamylideneacetic acids wereprepare by Liebermann’s method (Ber., 1896, 28, 1441). Thedo-acid was slightly impure, and melted at 115-1 1 7 O .4. The B-dimethyl- and trimethyl-acrylic acids were prepared bythe methods described previously (Trans., 1909, 95, 977).2. Hydrosorbic acid was prepared as follows.We wish t o express our thanks to the Research Fund Committeeof the Chemical Society for a grant which has covered part of thecost of this investigation.THE EDWARD DAVIES CHEMICAL IAABORATORIES,UNIVERSITY COLLEGE OF WALES,ABERYSTWYTH.VOL. XCVII