8_joc_pages

8/8/2019 8_joc_pages

1/8

[COXTRIBETIOXRO M THE RESEARCHN D DEVELOPMENTEPARTMENT,. S. NAVAL OWDERACTORYReaction of the Acid Chlorides of Aromatic Acids

with Bromine and Silver Oxide'F. A. H. RICE A N D W. MORGANROTH*

Received June 4, 1956I t has been found that the acid chlorides of several aromatic acids on treatment with silver oxide and bromine in carbontetrachloride solution loose carbon dioxide. The acid chloride is subst ituted by the halide.It has been reported3 th at when t he acid chloridesof ac etyla ted h exonic acids ar e dissolved in carb ontetrachloride and heated a t reflux temp erature withsilver oxide an d brom ine, th e acid chloride loses car-bon dioxide an d form s th e aldehpdo-l-bromo-penta-0-acetyl-pentose. Either acetic anhydride or ace-tyl chloride3 react with mixtures of silver oxide an dbromine an d af ter respectively losing 2 moles and 1

mole of carbon d ioxide, form m ethy l bromide.Although t he product formed by the reaction ofacid chlorides with silver oxide and bromine is es-sentially the same as that obtained by the decar-boxyla tion of th e silver sa lts of organic acids by re-action w ith bromine,4 th e acid chlorides, in contrast

like the sugar acid chlorides, would react to formcarbon dioxide and t he corresponding halide.Benzoyl chloride was found to react, with silveroxide and bromine to yield bromobenzene. The m-and p-nitrobenzoyl chlorides formed the corre-sponding rn- and p-bromonitrobenzenes. Kaph-thoyl chloride also reacted, altho ugh slowly, underthe same conditions to form bromonaphthalene.Th e reaction as measured b y th e evolution of car-bon dioxide was essentially quantitative (Table I).A possible mechanism for the above reaction isthat the acid chloride reacts with silver oxide toform th e silver salt of t h e acid and silver chloride.The silver salt would then react with bromine toTABLE I

DECARBOXYLATIONF AROMATIC CID CHLORIDESITH BROMINEN D SILVEROXIDECOZevolved.Equivalent inWeight, ml. 0 .1 N HCl Compound" w p . , OC .Compound g. Calc'd Obsv'd Isolated Observed Literature

~~ ~ ~

Benzoyl chloride 1 . 0 143 140 Bromobenzene 155-1 57 155Op-Xitrotwnzovl chloride7 1 95 228 211 p-Nitrobromo- 125-127 126-1278t9(b.p.)(m.p. 72-73) benzenem-Sitrobrnzoyl chloride7eT1 2.0 216 210 m-Nitrobromo- 56 5610,ll

(m.p. 32-33) benzene(m.p. 52-53)

Yaphthoyl chloride12 1.87 196 116 Bromonaphthalene 59 59'3

a Th r compounds gave the cor] rct elemental analyses.

to the silver salts are easily prepared in an anhy-drous condition and hence are more convenient touse than the silver salts. We were not able to findth at t he decarboxylation of aro matic or aliphaticacids via their acid chlorides had been studied andhence it was considered of interest t o investigateseveral arom atic acid chlorides to find ou t if the y,

(1) Published with permission of the Bureau of Ordnance,Navy Department. The opinions and conclusions are thoseof the authors.(2) Graduate Student at the Ohio State University,Columbus, Ohio. Appointee fo r the summer of 1955 underthe summer Research program of the Research and De-velopment Department, U . s. Naval Powder Factory.(3) F. A. H. Rice, Abstracts 0.f the 198th Meeling of th eAmerican Chemical Soczely, Minneapolis, Minn., 21D(1955); F. .4. H. Rice, J . Am . Chem. Soc., 78, 171 (1956).14) J. Kleinberg, C h e m Revs ,40, 381 (1947).

1388

(5) I,. Birckenback, J. Goubeau, and E. Berninger, Rer.,65 , 1339 (1932); W. Bockemuller and F. W . Hoffman, iinn.,519, 165 (1935); C. C. Price, Reactions at Carbon-CarbonDouble Bonds, Interscience Publisheis, New York, h'. Y. ,p. 55 (1946).(6) J. H. Gladstone, J . Chem. SOC., 5, 241 (1884):W. Ramsav and S. Young, J. Chem. Soc., 47 , 640 (1885).( 7 ) H. &lever,Monatsrh, 22 , 425 (1901), Org. Syntheses,Coll. Vol. 1, 2nd ed., 394 (1941).(8 ) J. H. CoRte and E. J. Parry, Be?., 29, 788 (1896).(9) o-Bromonitrobenzene has m.p. 43", F. Ullman, Ber. ,29, 1878 (1896).(10) I. Hrilbron and H. R I . Bunbury, Dictionary ofOrgnnic Compounds, revised Ed., Vol. I, Oxford UniversityPress, New York, S . Y., p. 350 (1953).(11) L . Claison and C. M. Thompson, Ber., 12, 1942(1879 .(12) P. T'ieth, Ann., 180,305 (1876).(13) A. Michaelis, Ann., 321, 141 (1902), footnote p.246.


2/8

D E C E M B E R 1956 B R O M I NE A N D S I L V E R O X I D E ON AROMATIC ACID CHLORIDES 1389give th e p r o d ~ c t ~ , ~COOBr which when heatedwould give R X + C02.4,6That the above mecha-nism ma y no t be the tr ue one, is suggested by the ob-servation that when either the acid chloride of D-gluconic acid penta-O-acetate3 or an aromatic acidchloride is added slowly to a boiling mixture of bro-mine and silver oxide in carbon tetrachloride, car-bon dioxide is immediately and continuouslyevolved. On the other hand, refluxing the acidchloride with silver oxide does not lead t o the im-med iate formation of t he silver salt of t h e acid . Onth e contrary, after four hours heating only trac es ofsilver salt can be found.

E X P E R I M E N T A LPrepa ration of the acid chlorides fr om the free acid. The acidchlorides were prepared by heating the corresponding acidwith thionyl chloride at reflux temperature and, after con-

centrating the solution to dryness under reduced pressurea t room temperature, crystallizing the resulting product frompetroleum ether (b.p. 30-60'). Before use the acid chlorideswere dried under high vacuum at room temperature. Re-agent grade benzoyl chloride was used.Reaction of acid chloride with bromine and silver oxide.Approximately one gram of the acid chloride was dissolved in

approximately 50 ml. of carbon tetrachloride in a three-neck 250-ml. flask. The carbon tetrachloride had been previ-ously dried over phosphorus pentoxide and then redistilled.An excess amount of silver oxide (2.5 g. dried over phos-phorus pentoxide in a high vacuum a t 100' for 24 hours)and 2 g. of redistilled bromine in 20 ml. of dry carbon tetra-chloride, was added and the mixture was stirred and heatedunder reflux. A stream of nitrogen from which traces ofcarbon dioxide had been removed by bubbling the gasthrough saturated aqueous sodium hydroxide and from whichmoisture had been removed by bubbling the gas throughconc'd sulfuric acid was used to sweep out the carbondioxide as it was formed. After the gases had passed throughtwo traps immersed in Dry Ice-Acetone, to remove anytrace of bromine, the carbon dioxide was absorbed in 0 .2 Naqueous barium hydroxide. The amount of carbon dioxideevolved was determined by titrating the barium hydroxidesolution with 0.1 il'hydrochloric acid and subtracting thehlank which had been run without th e addition of the acidchloride, but otherwise under the same conditions. Table Ishows the amount of carbon dioxide evolved from a numberof acid chlorides.The decarboxylated product was isolated by filtering thecarbon tetrachloride solution, concentrating i t to dryness anddistilling or crystallizing the product from ethanol.

Acknowledgment. We wish to thank Mrs. P. P.Wheeler for performing t he microanalyses.INDIAN EAD,MARYLAND


3/8

280 COMMUNICATIONS VOL. 26A Convenient Synthesis of Alkyl Halides from mercuric oxide, and reaction in light gives poly-

Carboxylic AcidsSir:

The salts of R variety of metals and carboxylicacids upon treatment with halogens lead to thehalogenative decarboxylation reaction RCOOM +X,+RX + MX + CO,.' Of these reactions, thatof the silver salt (generally termed the Hunsdieckerreaction) appears to be the most useful.' Thisreaction has the practical disadvantage that thesilver salt must be relatively pure and must bescrupulously dry in order to obtain satisfactoryyields. In the course of our studies2 on the mecha-nism of the decompositionof the acyl hypobromiteintermediate' in the Hunsdiecker reaction, we a btempted to prepare this intermediate in anotherfashion. This has led to what appears to us t o be auseful preparative method, as reagents and opera-tions are much more convenient than the silversalt-bromine reaction.Treatment of a slurry of excess red mercuricoxide in a refluxing solution of an aliphatic car-boxylic acid in carbon tetrachloride with approxi-mately one equivalent of bromine in the dark led toexcellent yields of the corresponding alkyl bromide.For example, treatment of 0.25 mole of stearic acidwith 0.25 mole of bromine and 0.19 mole of redmercuric oxide in 150ml. of carbon tetrachloride forone hour gave a 93% yield of crude heptadecylbromide, m.p. 22" ( l k 3m.p. 32" for pure material).The presumable stoichiometric equation is asfollows:2 RCOOH + HgO + 2 Brp+2 RBr + HgBrt + H20 + 2 Co t (1)

Since our original observation, the reaction hasbeen found to go in fair to excellent yields withcyclopropanecarboxylic acid and bromine14 with9,10-dihydro-9,10-ethano-9-anthroiccid with bro-mine in carbon tetrachloride and with iodine incyclohexane,5 with lauric acid and bromine,e withstearic acid and iodine,6 and in poor yield t o give1,3dibromopropane from glutaric acid.6 No 7-bu-tyrolactone was found in the latter case.The reaction gave poor yields with benzoic acidand bromine. Tetrachloroethane may also be usedas solvent.4Silver oxide may not be substituted for

(1) For leading references see: (a) H . Hunsdiecker andC. Hunsdiecker, Ber ,7J , 291 (1942); b)R.G Johnson andR. K. Ingham,Chem.Revs., 56,219 (1956); (c)C. . Wilson,Org. Reactions, 9,332 (1957).(2 ) S.J. Cristol, J. R. Douglass, W. C Firth, Jr , nd R.E. Krall, J . Am. Chem. Suc., 82, 1928 (1960).(3 ) For comparable results with the silver salt see: J. W.

bromination.When either exo- (I) or endo-5,6,7,8,9,9-hexa-ch10ro-1,2,3,4,4a15,8,8a-octahydro-exo-endo1,4,5,8-dimethano-2-naphthoic acid (11)2was treated underthese conditions, a mixture of 71% em-(111) and29% endo-bromides (IV)z was formed. This isprecisely the same mixt,ure of bromides obtainedfrom the silver salt of either acid with bromine.2This suggests that both procedures lead to the sameintermediate RCOOX. The reaction may involvethe existence of the mercuric salt although (a) it hasbeen reportedla that mercury salts of acids such asstearic acid do not give good yields following thenormal Hunsdiecker reaction, and (b) glutaricacid does not. give ybutyrolactone, whereas thesilver (and presumably the mercury) salt gives thelactone. It seems most likely that the mercuric oxidegives a positive halogen species: which reacts withthe carboxylic acid to give the acyl hypohalite.If this is the case, and if equation (1) represents thestoichiometry of the reaction, we do not under-stand why the water formed does not interferewith the reaction as it apparently does in the Huns-diecker procedure where glassware and chemicalsneed to be scrupulously dry.' I n any case, the pre-parative value of this procedure lies in its conven-ience and simplicity in comparison to those proce-dures involving preparation of silver or mercurysalts.

"3

c1 COzH/ Clc1 I

II11 IV Br

Acknmledgment. The authors are indebted toProfessor John S. Meek, D. T. Osuga, P. W. Jen-ningsand n/IissJ. S.Nelson for permission to mentiontheir work previous to publication. W. C. F. isfurther indebted to the Shell Development Com-pany and the University of Colorado for researchfellowships.DEPARTMENTF CREM~STFU STANLEY. CRISTOLUNIVEESITT OF COLORADO WILLIAM . FIRTH,R.BOULDER,ow).

Received October 21 , 1960H.'Oldham, J.-CChem.Soc., 100 (1950).(4 ) J. S. Meek and D T. Osuga, unpublished work.(5)J. S.Meek and P. W. Jennings, unpublished work.( 6 ) S. J. Cristol and J. S.Nelson, unpublishedwork. (7 ) W. Brenshede and H.J. chumacher, 2. physikal .Chem., 29B, 356 (1935); Z. norg. Chem., 226, 370 (1936).


4/8

FEBRUARY965 MODIFICATIONSF THE HUNSDIECKEREACTION 415the crude product produced recovered alcohol, 198 g. of 1,1,7-tri-hydroperfluoroheptyl benzoate, b.p. 155" (0.5mm.), and 295 g. of1,1,7-trihydroperfluoroheptyl orthebenzoate, b.p. 187" (0.1mm.), 62yc ield based on unrecovered alcohol.

Anal. Calcd. for C28H14F3803: , 31.05; H, 1.29. Found:C, 31.21; H , 1.36.l,l,S-Trihydroperfluoropentyl h1orocarbonate.-A solution of69.6 g . (0.3mole) of 1,1,5-trihydroperfluoropentanol nd 5.4g.(0.3mole) of water w as added intermittently over a period of 1.25hr. to a mixture of 26.4 g. of ferric chloride in 60 ml. of carbontetrachloride at 76". Large amounts of phosgene and hydrogenchloride were evolved over a period of 5 hr. After the addition of2.5ml. more of water , the reaction was allowed to continue anadditional 8 hr . After cooling, the entire reaction mixture wasdissolved in ether, washed very quickly with cold water, dried,and distilled. The fractionation gave recovered alcohol, 40 g.(6097,) f the chlorocarbonate, b.p. 53" (13 mm.), and 15 g.(217,)of the bis carbonate.A part of the 1,1,5-trihydroperfluoropentyl chlorocarbonate(6.0 g ., 0.02 mole) was added to excess methanol in ether a t 50".Distillation after work-up yielded 4.3 g. (70y0 f methyl 1,1,5-trihydroperfluoropentyl carbonate, b.p. 50' (0.15mm.).Methyl chlorocarbonate (10.4g., 0.11 mole) was stirred with23.2 g. (0.1mole) of 1,1,5-trihydroperfluoropentanol n chloro-

form containing 0.02 mole of titanium tetrachloride for 5 hr. at50'. After work-up similar to above experiments, fractionationof the product yielded 24.2 g. (80%) of the methyl fluoro alcoholcarbonate, b.p. 46" (0.1 mm.).The two methyl fluoro alcohol carbonates from these experi-ments were found to be identical by infrared and n.m.r. analysesand determination of the same retention times by g.1.p.c.1,1,7-Trihydroperfluoroheptyl hlorocarbonate was prepared ina similar manner except the alcohol and water were added por-tionwise simultaneously. The chlorocarbonate was obtainedin 40% yield, b.p. 73" (14mm.).A n a l . Calcd. for C8H3ClF1202: C, 27.70; H, 1.54. Found:C, 27.81;H , 1.44.Phosgene was bubbled through a mixture of 22.7 . (0.1mole) of1,1,5-trihydroperfluoropentanol nd 8.1 g. (0.05 mole) of ferricchloride for 6 hr. at 50". Less than 10% of chlorocarbonate wasobtained.Acknowledgment.-This paper is related to an obser-vation by one of us (M . E. H.) at t he U . S. N a v a lOrdnance Laboratory, Si lver Spring, Maryland. T h emany stimulating discussions with Dr. D. V. Sickmanand Dr. 0. H. Johnson are gratefully acknowledged.

Modifications of the Hunsdiecker Reaction'"JOHN A. DAVIS, AMESE R Y N K , ~ ~A MCAR ROLL,'^ JIMB U N D S , ~ ~N D DOUGLASOHN SON^^

Department of Chemistry, Washburn Unive rsity of Topeka, Topeka, KansasReceived August 18, 196'4

Bromodecarboxylation of organic acids by the Cristol-Firth modification of the Hundsiecker reaction usingthe free acid and red mercuric oxide was found to be much more effective than the modification using the acidchloride and silver oxide. A study has been made of the possible use of oxides other than mercuric oxide andof the effectiveness of various solvents.Replacement of the carboxyl group in organic acidsby a halogen atom , especially bromine, by tre atm en t ofthe anhydrous silver salt of the acid with bromine,chlorine, or iodine in an inert solvent is commonly

known as t h e H u n s d i e c k e r r e a c t i ~ n . ~ - ~ields aregenerally quite good (usually better than 60%), butthe reaction is extremely sensitive to trace amounts ofwa ter, tlle p resence of which leads to the recovery ofunchanged acid. Unfo rtunately, the preparation ofdr y silver salts of carbox ylic acids is frequently verydifficult and , because such salts a re usually q uite sensi-t ive to heat also, they are &n quite hard to drythoroughly.Several years ago there appeared a report5 that theacid chloride of penta-0-acetyl-D-gluconic acid under-goes smooth decarboxylation when heated with bro-mine and silver oxide in carbon tetrachloride, furnish-ing aldehydo-1-bromo-D-arabinose penta-0-acetate in

an excellent yield. A second report6 described thereactions of benzoyl chloride an d thre e other aro maticacid chlorides with brom ine and silver oxide in carbontetrachloride.An investigation of this modification of the Huns-diecker reaction was started using the following acidchlorides: benzoyl chloride, n-butyr yl chloride, phthal-(1) (a) This work was made possible by Grant R897-B from the PetroleumResearch Fund, administered by the American Chemical Society: (b)American Chemical Society Petroleum Research Fund Scholar.(2 ) R. G. Johnson and R. K . Ingham, Ch em. Rev . , S6, 219 (1956).(3 ) C. V. Wilson, Org. Reactions , 9, 332 (1957).(4) C. W . Shoppee and R. J. Stephenson, J . Ch em. Soc . , 2230 (1954).(5) F. A. H . Rice, .I. A m . C h e m. Soc . , 7 8 , 3173 (1956).(6)F. A. H . Rice and W . Morganroth, J . Ow . C h e m . , 11, 1388 (1956).

oyl chloride, p-nitrobenzoyl chloride, and p-chloro-benzoyl chloride.The silver oxide was carefully dried as was all theglassware and the carbon tetrachloride, bromine, andacid chlorides were redistilled before use. Althoughnumerou s variations of th e reaction co nditions weretried, only t race amounts of the desire(. bromideswere obta ined by fraction al distillation of the reactionmixtu res. Ho wev er, fair yields of bromo benzene wereobtained from silver benzoate by the original Huns-diecker reaction.Fu nd , Cristol , and F irth have reported' th at t reat-ment of a slurry of excess red mercuric oxide in a re-fluxing solution of stearic acid in carbon tetrachloridewith approximately an equivalent amount of brominein the dark gave a 93% yield of crude heptadecylbromide. Th e reaction also was reported t o givepoor yields with benzoic acid arid glutaric acids, andfair to excellent yields with cyclopropanecarboxylicacid, 9,lO-dihydro-9,lO-ethane-9-ant hronic acid, andlauric acid. As soon as we learned of the Cristol-Firthmodification, its apparent convenience and simplicityin comparison to those procedures involving prepara-tion of silver salts or acid chlorides immediately sug-gested a broad s tu dy of this modified proced ure usingdifferent classes of carboxylic acids an d t he use ofsolvents other than carbon tetrachloride. Since mer-curic oxide is relatively expensive and mercury com-pounds a re tokic, a stu dy also was made of the possi-bility of using other oxides for this reaction.(7 ) Stanley J. Cristol an d William C. Firth, Jr., i b i d . , 96 , 280 (1961)


5/8

416 DAVIS,HERYNK,ARROLL,UNDS, ND JOHNSON VOL. 0TABLE

PERCENTYIELDSBASED N WEIQHT F BROMIDEECOVEREDChloroacetic CzHzCli Bromochloromethane 38 68-73 (68-69)b 1.4795% 1.4832)bn-Butyric C2HzC1, 1-Bromopropane 53 70-74 (72)" 1 43512' (1.4348yIsobutyric C H C 4 2-Bromopropane 21 59-62 (59) 1 .425026(1,4254)2-Methylbutyric C2HzClr 2-Bromobutane 61 90-94 (91 1 . 30126 (1.4366)Hexanoic CCl4 1-Bromopentane 31 125-130 (128) 1 444031 1.4450)Heptanoic cc4 1-Bromohexane 37 150-158 (159) 1 .447028 (1 .4478)Octanoic cc4 1-Bromoheptane 31 175-180 (177.5) 1 .446231 1.4505 )Dodecanoic cc14 1-Bromoundecane 46 55-60 (114)d 1.456826 1.456 9)

Yield, '70 B.p., OC." nDOC.aAcid Solvent Product

a Numbers in parentheses refer to literature values. Literature values of refractive index are given for 20". C. L. Stevens, T. K.The literature values for 1-bromopropane and for all th e com-Value given for 0.05 mm.; liturature valueMukherjee, and V. J. Traynelis, J.A m . Chem. Soe., 78, 2264 (1956).pounds below it in the table are taken from A. I. Vogel, J. Chem. SOC.,636 (1943).given for 5 mm.TABLE1

PERCENTYIELDSBASED N AMOUNTF CARBON IOXIDEPRODUCED~Chloroacetic 71 (38)Trichloroacetic 82 (13)

Acid8 CChb CiHnClrb

Propionic 94n-Butyric 99 (53)Isobutyric 90 (21)2-Methylbutyric 77 (61)2-Ethylbutyric 80 87 (17)Trimethylacetic 85 (13)Hexanoic 88 (31)Cyclohexanecarboxylic 88Heptanoic 90 (37)Octanoic 59 (31)2-Ethylhexanoic 76 92Decanoic 69Lauric 67 (46)Myristic 91Palmitic 90 81Stearic 95Phenylacetic 41 71Diphenylacetic 51Benzoic 48 83p-Toluic 40 76Anisic 54p-Nitrobenzoic 0 70Phthalic 85Terephthalic 20Malonic 19 33Glutaric 85Hexanedioic 53Octanedioic 29 75Decanedioic 66 79Using red mercuric oxide and either carbon tetrachloride orlll,2,2-tetrachloroethanea solvent. Numbers in parentheses

are per cent yields baaed upon the amount of organic bromiderecovered by fractional distillation.

After trying a number of variations of the method,it was found that best yields were obtained when theacid, the red mercuric oxide, and the solvent weremixed and stirred with a magn etic stirrer. Th e mix-ture was then h eated an d a small fraction of th e bro-mine was added. If a reaction did not occur spon-taneously, heating was continued until the reactionstar ted ; then t he remainder of th e bromine was slowlyadded. Th e mixture was kept warm for 1 hr. , thenfiltered and washed w ith 5y0 odium hyd roxide solution,then w ith water, and dried over anhydrous magnesiumsulfate. It was then filtered and the bromide wasseparated by fractional distillation and identified b y itsboiling point an d refractive index (see Table I).

As the isolation by fr actio nal distillation of a sm allam oun t of liquid produ ct from a relatively large volumeof solvent is a time-consuming operation and normallyis not quantitative, a large number of determinationswas made in which the extent of reaction was deter-mined by measuring the am oun t of carbo n dioxideevolved. In these determinat ions 0.01 mole of acidwas mixed with 5 g. (an excess) of red mercuric oxide(or an equivalent amo unt of other oxide) and 50 ml.of solvent. Th e mixture was warmed and 2 ml. ofbromine was slowly added. The carbon dioxide wasswept out of the ap paratus w ith ni trogen and absorbedin a standard barium hydroxide solution. The bariumcarbonate precipitate was removed by filtration and theexcess barium hydroxide was t i t rated with standardacid. See Table I1 for yields obtained when carbontetrachloride and 1,1,2,2-tetrachloroethane ere usedas solvents.Of t he oxides th at were tested a s replacements forred mercuric oxide, only the five listed in Table I11showed any reaction. Propionic acid dissolved intetrachloroethane and treated with bromine in th epresence of a n oxide of each of t h e following gave noreact ion: aluminum, ant imony, barium, bismuth,calcium, cobaltic, cupric, cuprous, ferric, magnesium,nickelic, stannic, zinc, and sodium and t i t anium di -oxides.TABLE11

PERCENTYIELDSBASED N AMOUNTF CARBON IOXIDEPR O D U C ED O

-Yield, %-HgOb-1-Acid low) AgnO PbO Pbso4 CdO

Propionic 87 78 42 45 8Palmitic 76 12 5 (CClr)Benzoyl chloride 7 (CCla)Palmitoyl chloride 8 ( c c 4 )

Acid chlorides

Butyryl chloride 45a Using 1,1,2,2-tetrachloroethanea solvent and oxides otherthan red mercuric oxide.Fo r th e effectiveness of solven ts othe r th an carbo ntetrachloride and tetrachloroethane see Table IV.

DiscussionIn this invest igat ion i t was found that the Cristol-Firth method using red mercuric oxide and the free acidgave much m ore decarboxylation than did the method


6/8

FEBRUARY965 p31-Hl COUPLINGOR STRUCTUREETERMINATION 417

PERCENT

AcidPalmiticPhthalicTerephthalic

TABLEVPRODUCED'YIELDSBASED N AMOUNTF CARBONIOXIDE

Yield, '$&Nitro- Bromo- Chloro-Ben- ben- ben- ben- CzClr- C&la- Hex-zene nene zene nene Fz F3 an e69 82 76 67 71 58 400 0 32

26Propionic 79 61 2 40Benzoic 6 48 41 0Stearic 812-Ethylbutyric 60 43

a Using red mercuric oxide and different solvents.

using silver oxide an d the acid chloride. Th e Cristol-Firth method is simpler than the original Hunsdieckermethod in th at it does not require the preparation of th edry silver salt. In m any cases higher yields were ob-tained with tetrachloroethane as solvent than with car-bon tetrachloride. This probably was due to the higherboiling point of th e tetrachloro ethane which permitted ahigher reaction temperature. Bromobenzene and tet-rachlorodifluoroethane seem to offer soine promise asoth er solven ts for this reaction. Yellow mercuric oxidewas found to be almost as effective as red mercuricoxide. As a general rule arom atic and dicarboxylicacids underwent less bromodecarboxylation than didaliphatic monocarboxylic acids.

least 1 hr., then filtered, washed, and dried, and the organicbromide was separated by fractional distillation. The prepara-tion of 1-bromohexane is typical of the method used.Preparation of I-Bromohexane from Heptanoic Acid.-A fewdrops of a solution containing 16 g. (0.1 mole) of bromine in 50ml. of dry carbon tetrachloride produced an immediate reactionwhen added to a warm, stirred mixture of 13.0 g. (0.1 mole) ofheptanoic acid and 22 g. of red mercurir oxide in 150 ml. of dr ycarbon tetrachloride. The remainder of the bromine solution wasadded slowly and the reaction mixture was refluxed for 1 hr.The mixture was then filtered, washed with 5y0 sodium hy-droxide solution and then with water, and dried with anhydrousmagnesium sulfate. Careful fractional distillation of the solutiongave 6 g. of I-bromohexane, b.p. 150-159", 12% 1.4470.T o determine the per cent yield based on the amount ofcarbon dioxide produced, 2 ml. of bromine was slowly added to awarm, stirred mixture containing 50 ml. of solvent, 0.01 mole ofacid, and 5 g. of red mercuric oxide in a 500-ml., three-neckflask. The flask was fitted with a dry nitrogen inlet, separatoryfunnel fo r addition of the bromine, and a reflux condenser. Thecarbon dioxide produced was swept out of the flask by nitrogenand passed through three Dry Ice traps to remove all brominevapor and then absorbed in standard barium hydroxide solution.The barium carbonate precipitate was filtered off and the excessbarium hydroxide was titr ated with standard acid. The follow-ing is typical of the method used.Bromodecarboxylation of Palmitic Acid.-Bromine (2 ml .)was added slowly to a warm, stirred mixture containing 50 ml.of carbon tetrachloride, 2.564 g. (0.01 mole) of palmitic acid,and 5 g. of red mercuric oxide. The carbon dioxide pro-duced was swept out of the flask by nitrogen and absorbed in125.0 ml. of standard 0.2 N barium hydroxide solution. Thebarium carbonate precipitate was filtered off and the excessbarium hydroxide titrated with standard hydrochloric acid,yielding 0.0090 (goyo) mole of carbon dioxide.

Acknowledgment.-Acknowledgment is mad e to th eExperimental

For the preparation and isolation of the organic bromides, 0.1mole of bromine was slowly added to a warm, stirred mixture of0.1 mole of acid and 0.1 mole of red mercuric oxide in 150 to 200ml. of ,solvent. The reaction mixture was then refluxed fo r a t

donors of T he Petroleum R esearch Fu nd , administeredby the American Chemical Society, for support of thisresearch and to the E. 1. d u Pant de Nelllours andCo mp any f or furnishing samples of tetrachlorodifluoro-ethan e an d trichlorotrifluoroethane.

Synthesis and Reactions of Some Triphenylphosphazines. The Use ofLong-Range P3I-H1Coupling for Structure DeterminationGURDIALINGH N D HANS IMMER ~

Department of Chemistry, University of Cincinnati, Cincinnati d l , OhioReceived Jul y 17, 1964

Some 8-N-alkylidene- and -arylidenehydrazinotriphenylphosphonium romides have been synthetized byreacting triphenylphosphine dibromide with appropriate hydrazones. Dehydrobromination of these phos-phonium bromides with sodamide in liquid ammonia led to the corresponding triphenylphosphazines. Thesetriphenylphosphazines are nucleophiles as is shown by their reactions with methyl and ethyl iodides t o yielda-N-alkyl-8-N-alkylidene- and -arylidenehydrazinotriphenylphosphonium odides. Thes tructures of thesephosphonium iodides have been verified through n.m.r. spectroscopy. The ultraviolet and visible absorp-tion data of triphenylphosphazines are compared with those of the corresponding hydrazones.Recently we became interested in the synthesis andreactions of organophosphorus compounds containinga -N=P 6 linkage, such as triphenylphosphinalkyl-imines2 and triphenylphosphin- and d isub stitutedaminoimines. 3 , 4 These compounds reacted readilywith methyl and ethyl iodides to give dialkylamino-triphenylphosphonium iodides2 and a-N-alkylhy-drazino- and a-S-alkyl-P-N-disubstituted hydrazino-triphenylphosphonium iodides14 respectively. Hy -

drolysis of dialkylaminotriphenylphosphonium iodidesand a-N-alkyl-p-N-disubstituted hydrazinotriphenyl-phosphonium iodides furnished the correspondingsecondary amines and 1 I Ztrisub st i tuted hydrazines,respectively, in excellent yields. Th us , these com-pounds, containing a phosphorus-nitrogen doublebon d, represent a convenient tool for the syn thesis ofcertain, especially sterically hindered, seco ndary am inesand 1,l Btrisu bst i tuted hydrazines.(1) Author to whom inquiries should be addressed.(2 ) H. Ziinmerand G. Singh, J . O w . C h e m . . 46,483 (1963);A n o e w . C h e m . ,

(4) H. Ziminer and G. Singh, J . 0 7 0 . C h e m . , 28, 1579 (1964).

Th e structures of all organophosphorus compounds,mentioned above, were proved by elemental analyses,chemical behavior, and ultraviolet and n.m.r. spectro-scopic studies. Th e latte r method proved to be of11, 574 (1983):A n g e w . C h e m . , I n ter n . Ed. Eng., '2, 395 (1963).

(3) F.Kaplan, G . Singh, and H. Zimrner, J . P h y s . C h e m . , 61 , 2509 (1963).


7/8

Notes J.Org. C he m. , Vol. 44 , ~VO.9, 1979 3405T a b l e I. Ti t ra t ion of Organol i th ium Reagents Us ing N-Benzylidenebenzylamine (1 a s Ind ic a to ra

Watson andE a s t h a m Ci t ra t ion c ond i t ionso rga no l i th iumb s o lven t me tho d A me tho d B me th od to t a l a lka l idn -B uLi in h e xa nes a mple 3.

s a mple 2sample 1s a mple 2s a mple 1s a mple 2

s e c -B uLi in c yc lohe xa n e

t-BuLi in pentan e

PhLi in be nz e ne -d ie thy l e the r

Et ,OT H FT H FEt,OT H FT H FEt,OT H FT H FEt,OT H Fbe nz e nehe xa ne

1.62e 1.60 1.761.61e1.6sesf 1.691, 0 e 1.49 1.641.50e1 15e8f 1.141.26e 1.25 1.181.24e1.46e,f 1.46l . O l e 1.00 1.960.9ge1 0oel . O o e

a Each va lue is an average of tw o or mo re t i t ra t ion s . The o rga no l i th ium s o lu t ions we re pu rc has e d f rom Ald r ic h . Thec onc e n t ra t ions ind ic a te d by A ld r ic h we re 1.6 M fo r n -B uLi , 1.4 M for sec-BuLi , 1.6 M fo r t -B uLi, 1.67 M fo r PhLi . 1 , l O -Phe na n th ro l ine a s ind ic a to r , be nz e ne o r he xa ne a s s o lve n t , s e c -bu ty l a l c oho l /xy le ne a s ac id s o lu t ion , a c c o rd ing to ref 2.ga no l i th ium s o lu t ion by 10 m L of dis t il led wate r . e s e c -B u ty l a l c oho l /xy le ne a s a c id s o lu t ion . f B e nz o ic a c id /TH F a s a c id

Obta ine d b y t i t r a t ion by a s t a nda rd a c id u s ing phe no lph tha le in a s ind ic a to r , a f t e r hyd ro lys i s o f a 5 -mL a l iquo t o f t he o r -s o lu t ion ,benzylidenebenzylamine (1) are known to produce a redpurple color? and t his coloration remains inten se as longas carbanion is present in the solution. We used thisprop erty for th e analysis of organolithium reagents by twomethods (see Scheme I ) .In method A, the organolithium reacts with a solutionof an excess of th e Schiff base 1 by addition and meta-lation. Th e colored anion 3 is obtained by metalation ofthe Schiff base by means of RLi or the lithium amide 2formed by addition. In method B, the organolithium isconverted to lithium diisopropylamide (4), which producesanion 3 from a few drops of Schiff base 1. Th e l i thiumcompound RLi is quantitatively transformed into 2 an d3 (method A) or 4 and 3 (method B) . Titra tion is madeby addition of an acid solution which reacts both with thelithium amide 2 or 4, and with the colored anion 3. At th eend point, the added acid is equal to the initial qua ntityof RLi. Results are summarized in Tab le I.These methods have the advantage of using organo-lithium compounds in the common conditions of use ofthese reagents in various solvents such as diethyl ether,tetrah ydro fura n, benzene, and hexane. These are singletitration s, simple and rapid to realize in the laboratory,and pre sent a sharp and easy to observe end point. Th eSchiff base 1, easily prepared from benzylamine andb e n ~ a l d e h y d e , ~ , ~s a liquid a t room temperature and canbe stored as a solid a t -30 OC. Finally, these method s canbe used to control the quality of the solvents.8

Experimental SectionSolv ents were drit?d on molecular sieves, then distill ed fromLiAIHl prior to use.M e t h o d A. A 5-mL aliquot of the solution to be analyzed wasadded a t room tempera ture under n i t rogen to a solution of 2 g(6) (a)T. Kauffmanr,,K. Habersaat, and E. Koppelmann,Chem. Ber.,110,638 (1977). (b ) L. I . Sivova, N. A. Sivov, R. A. Gracheva, and V. M.Potapov, Zh . Org. Kh i n . , 14, 791 (1978).(7) For a review see for example: R. W. Layer, Chem. Reu., 63, 489(1963).(8) For example, titrations (method A) by an identical acid solutionof an identical solution of n-Bu Lilhe xane in THF freshly distilled fromLAM4and TH F distilled some months prior to the experimentation yieldedN = 1.69 and N = 1.59, respectively. The difference between these twovalues is attributed to impurities contained in old THF.

0022-326317911944-3405$01.00/0

of imine 1 (in excess) in 10 mL of solvent (see Tab le I) . A strongcrimson color appeared immediately with the addition of or-ganolithium; the solution was then titrated by a 1 M solution ofsec-butyl alcohol in xylene or a 1 M solutio n of benzoic ac id inte t rahydrofuran.M e t h o d B. A 5-mL aliquot of the solution to be analyzed wasadded a t room temperature under nitrogen t,o a solution of 2 m Lof diisopropylamine (in excess) in 10 mL of solvent (see Ta bl eI) . Imine 1 (2-3 drops) was add ed to this mixture, and the crimsoncolor appeared immedia te ly . Th e solut ion was then t i t ra te d asin method A.In th e two methods, th e end point was reached when the colorof the solution became a persiste nt yellow.R e g i s t ry No. 1, 780-25-6;n-BuLi, 109-72-8; ec-BuLi, 598-30-1;t-BuLi, 594-19-4;PhLi , 591-51-5.

Photoassisted Cristol-Firth-HunsdieckerReactionA. I. Meyers* and M ichael P. Fleming

D e p a r t m e n t of Chemistry, Colorado State University,F o r t Collins, Colorado 80523Received March 28, 1979

A well-known route to aryl and alkyl bromides is theHunsdiecker reaction2 or its more recent m odification byCristol and Firth.3 The latter workers found that m ercuricsalts of carboxylic acids could replace th e more tediouslyprepared and sensitive silver salts in the key bromo-decarboxylation step upon treatment with bromine.Recent studies on the scope and mechanism4* of theCristol-Firth modification indicate th at the carboxylic(1) National Service Award (NIH) Postdoctoral Fellow, IF32CA05946-02.(2) Wilson, C. V. Org. Reac t . 1957, 9, 341.(3 ) Cristol, S. J.: Firth. W. C.. Jr . J. Ore. Chem. 1961. 26. 280(4) Davis, J. A.; Hernyk, J. ;Carroll, S.;Bunds,J.;Johnson, D. J . Org.( 5 )Bunce, N . J. J . Org. Chem. 1972, 37, 664.(6) Cason, J.; Walba, D. J . Org. Chem. 1972, 37, 669.

Chem. 1965,30, 415.

0 979 Ame r ic a n C he m ic a l Soc ie ty


8/8

3406 J. Org. Chem., Vol. 44, No. 19, 1979Table I. Conversion of RC 0,H to R Br (HaO-Br,- liahtP

Notes

R Br% yield% yie ld (wi thoutRC 0,H (wi th l ight )b l ight )

p-CIC,H,CO,IIp-NO,C, H,CO,H3.5-(NO., LC,H,CO ,H8 0 - e9 5 4 2 , 0 70 f9 7 Oe

3 ~ N O , - 4 % l - ~ - M e O d 6 H , C O , H 9 6 c - 4 0p -Br C, H,CO , 13m-BrC,H,CO,H 83o-CIC,H,CO,H 81m -Cl C, H, C O, Ho-ph thalic acid 4 2 85fn-C, H, ,CO,H 99 9 l fn - C , H, ,CO,H 90 90f11-C, H,,CO,H 85 95f

8 67 5o-MeOC,H,CO,H d

1-naph thoic ac id d

a React ions run in carbon te t rachlor ide a t re f lux, molarratios of RC0,H-HgO-Br, are 1.00 :1.50 :1.5 0, respective-ly. All yields are fo r pure (distil led or crystall ized) pro-ducts and were identi f ied by comparison wi th publ ishedIR and NMR da ta (Aldr ich or Sadt ler) . J. M. Kane andA. I. Meyers, Tetrahedron Let t . , 7 7 1 ( 1 9 7 7 ).polybrominated products . e See ref 5. Based on car-bon dioxide produced.lowe r in thos e instances wh ere isolation was a t t empted(see ref 4).acids form a diacyloxy mercury salt 1,which then leadsto the acyl hypobromite 2 followed by thermal decom-position to the alkyl bromide. During the course of other

Gave onlyActual isolated yields were mu ch

HgO ZBQ2RCOzH ---RCOZ),Hg- RC02Br- RBr1 2stud ies, we h ad occasion to investigate th e C FH reactionwith aromatic acids. T he observed trend@ is th at arom aticacids form ra ther insoluble mercuric sa lts and give loweryields tha n aliph atic acids. We now describe a furthermodification of the CFH reaction which simply involvesirradiating the re action mixture with a 100-W bulb. In thisfashion excellent and re produ cible yields of aryl an d alkylbromides were obtained (Tab le I). For those aromaticacids con taining electron-rich substituents (e.g., anisic acid)th e reaction gave only polybrominated products.

Exper imen ta l S ec t ionG e n e r a l P r o c e d u r e f o r L i g h t - A s s i s t e d B r o m o d e c a r b -oxlyation. Into a dry, nitrogen-pu rged, three-neck, 100-mL flaskcontaining a spin bar and fitted with a reflex condenser wereplaced the carboxylic acid (10.0mmol), carbon tetrachloride(reagent grade, 50 mL), and red mercuric oxide (B & A, 15.0mmol). Th e flask and an adjacent 100-W bulb were enclosed in

aluminu m foil. Th e mixture was heated to reflux in an oil bathwhile being irradiate d, and brom ine (B aker, "purified", 15.0 mmol)was cautiously added via syringe. Th e mixture was heated a treflux an d irradiated for 3 h, and cooled to room tempera ture.Saturated aqueous N aHC 03 (30mL) was added and the mixturewas vigorously stirred for 1 5 min. T he two-phase mixture wasvacuum filtered through a Celite pad and the pad was washedseveral times with chloroform. Th e organic phase of the filtratewas washed with saturated NaHC03 (30mL) and brine (30mL)and dried (M gS04 ). Removal of solvent and d istillation gave thebromide.Ack now ledgm ent. Financial assistance fo r this studycame from the Nation al Institu tes of He alth (CA-16051).Registry No. -C1C6H,C02H, 4-11-3;p-NO2C6H4CO2H,2-23-7;3 ,5 - (N02)2C6H3C02H,9-34-3; 3-N02-4-C1-5-MeOC6H2c02H,

71001-78-0; m-BrC6H4Co2H, 85-76-2; p-BrC6H,CO2H, 586-76-5;O-CIC&~CO~H,18-91-2; m-ClC&C02H, 535-80-8; o-Me0C&I4CO2H,0022-326317911944-3406$01.00/0

579-75-9; o-phthalic acid, 88-99-3; 1-naphthoic acid, 86-55-5; n-p-C1CsH4Br,106-39-8; p-N02C6H 4Br,586-78-7; 3,5-(N02)2 CBH 3Br,18242-39-2; 3-N02-4-C1-5-MeOC6H2Br,3603-16-7; m-BrC6H4Br,108-36-1;p -BrC6H8r ,106-37-6;o-ClC6H4Br, 94-80-4; m-ClC6H 4Br,108-37-2; o-BrC6H 4Br,583-53-9; n-C13H2,Br,765-09-3; n-C15HB1Br,629-72-1; n-C17H35B r, 508-00-7.

C13HnC02H, 544-63-8; n-C&1C02H, 57-10-3; n-C17H&02H, 57-11-4;

M a x i m u m O p t i c a l R o t a t io n of 2-Fluorooctane?S u r v e y of F l u o r i n a t i n g R e a g e n tsJacques Leroy,la Eric H ebert,lb and Claude W akselman'"*

C.N.R.S., 94320 Thiais, FranceReceived March 28, 1979

Optically active 2-alkyl halides a re of particular intere stas they can serve as models in the study of numerousreactions of organic chem istry. 2-Chloro-, 2-bromo-, or2-iodooctane s commonly used2 and their optical pur itiesare determined without am bi g~ ity .~ y co ntra st, however,the m aximum optical rotation of 2-fluorooctane remain sunknown, as no chemical correlation has been established,owing to the poor leaving-group character of fluorine.Thu s, only an estimate of optical purity has been madefor 2-fluorooctane (1) based on a correlation betweenmolecular rotation and bond refra~tion.~Recent results obtained with methyltri-n-butylfluoro-phosphorane5 (2) leading to 2-fluorooctane of highe r opticalrotation than th at of San Filippo a nd R omano4 (stated asabout 100% optical purity) have prom pted us t o checkother fluorinating reagents.6 Phenyltetrafluoro-phosphorane7 (3) , N - 2-chloro-1,1,2- rifluoroethy 1)di-ethylamine8 (4 ) (FAR), and (diethy1amino)sulfur tri-fluorideg ( 5 ) (DAST) were used according to slightlymodified procedures.CGH,,CH(OTs)CH3 + (n-C4Hg)3PFCH,+2C6H13CHFCH3+ octenes + ( ~ Z - C , H ~ ) ~ P ( O T ~ ) C H ~1)1C6H,3CH[OSi(CH3)3JCH3 C6HbPF,- +C5H,,CHFCH2CH3+ octenes + FSi(CH3)3+C6HSPOF23

(2)CGH13CHOHCH3 + (C2Hh)ZNCF2CHFCl-+41 + octenes + (C,H,),NCOCHFCl + H F (3 )Cp,H&HOHCH3 + (CzHS)zNSF3-+

51 + octenes + (CzH,),NSOF + H F (4 )(1) (a ) Centre d'Etudes et de Recherches de Chimie OrganiqueAppliquge; (b) Groupe de Recherche No . 12 .(2 ) M. Malissard, J. P. Mazaleyrat, and Z. Welwart,J . Am. Chem.SOC.,99 , 6933 (1977); E. Hebert, J. P. Mazaleyrat, and Z. Welvart, J . Chem.Soc., Chem. Commun., 877 (1977).(3 ) H. M. R. Hoffman, J . Chem. SOC., 24 9 (1964).(4 ) J. S.Filippo, Jr., and L. J. Romano,J. Org. Chem.,40, 1514 (1975).(5) Preliminary communication: J.Bensoam,J. Leroy,F.Mathey, andC. Wakselman, Tetrahedron Le t t . , 353 (1979).(6) G. Gelbard and co-workers have recently prepared (+)- (S)-2-fluorooctane, [ a I m ~ 9 0.2' (neat), in 60% yield from the mesylate of(-)-(R)-2-octanol y anion exchange resins. Private communication ona further publication in J . Chem. SOC., erkin Trans. I .( 7 )D. . Robert,G.N. Flatau,A. Cambon,and J. G. Rim . Tetrahedron,29 . 1877 (1973).

~~ ~~- - I(8) C. M. Sharts and W . A. Sheppard, Org. Reac t . , 21 , 12 5 (1974).(9) W. J. Middleton, J . Org. Chem., 40 , 5'74 (1975).

0 979 American Chemical Socie ty

8_joc_pages

Documents