BROUGHTON ON ANHYDRIDES AND ETHERS. IV.-On a New Reaction for the Production of Anhydrides and Ethers. By JOHN BEOUGHTON, B. Sc. Chemical Assistant Royal Institution. THE reactious which are employed for the preparation of the anhydrides of the monobasic organic acids are those originally discovered by Gerhardt where either the chloride of an electro-nemative radicle is made to act on the corresponding alkaline salt, .? giving rise to the production of an alkaline chloride and the anhydride ; or the same decomposition is indirectly superinduced * Communicated to the Chemical Society June 16th 1864. BROC'QHTON ON A NEW REACTION FOR THE by allowing the pentachloride or terchloride of phosphorus to act on the alkaline sslt. These methods therefore essentially consist rather in an almost synthetical formation of the anhydride by a process of double decomposition aualogous in it3 nature to those by which the com- pound and double ethers are produced than in a direct elimina- tion of the anhydride froin the salt of which the reactions for producing nitric and carbonic anhydrides afford familiar instaiices.In addition to the above methods is that described by Gal ( Compt. rend. lvi. 360) who by acting on caustic lime and baryta with the chlorides of acetyl and benioyl obtained the correspond- ing anhydrides. As this method obviously necessitates the employ- ment of the chloride of phosphorus its principle rests mainly on the same decomposition as that discovered by Gerh ardt. It was therefore thought that a reaction by which the anhydrides of the organic acids could be more directly eliminated from salts in the same manner as some inorganic anhydrides would possess considerable interest both in a practical and in a theoretical point of view.For this purpose several attempts were made to procure acetic and benzoic anhydrides by the action of boracic acid on the potassium-salts of these acids ;but this method as might probably have been foreseen failed to produce the desired substances. It then occurred to me to try the effect of bisulphide of carbon. This substance was shown by Freniy many years ago to be readily decomposed by heated metallic oxides into carbonic anhydride arid a metallic sulphide and also when heated with water to a high temperature to form sulphuretted hydrogen and carbonic anhydride (Schl agdenhauffen J.Pharm. [3] xxix. 491). It was therefore thought probable that by acting on the dry metallic salts of the organic acids with bisulphide of carbon the metal would be converted into sulphide and the anhydride set free. With this view the following experiments were per-formed :-Crystallised acetate of lead was dried for several hours at about l?O°C.,and reduced to as fine a state of division as possible and a small quantity was placed in a strong glass tube which was then one-third filled with dry bisulphide of carbon sealed and heated in an oil-bath to about 15GOC. After an hour's heating the contents of the tube had become quite black and after a few hours' exposure the tube was removed from the bath allowed to PBODUCTION OF ANHYDRIDES AND ETHERS.2s cool and then opened when a violent escape of gas took place attended with a strong pungent acid smell. This gas on being allowed to pass into baryta-water was found to be carbonic anhy- dride. Several strong tubes of hard glass were thencharged with 20 grammes each of dry acetate of lead and as much bisulphide of carbon added as was necessary to make on agitation with the acetate a mixture of a creamy consistency. The tubes being then rather more than one-third full were sealed and heated in the oil-bath to a temperature of 165°C. The mixture quickly assumed a black colour and after some hours' heating one of the tubes by exploding with great violence gave warning that a large amount of gas had been liberated.After this it was found ad- visable to open the tubes once a day in order to let the carbonic acid escape ;and with this precaution the digestion was continued till it was found that on opening the tubes only a slight rush of gas took place. The reaction was then juciged to have practically terminated. The liquid contents of the tubes were then poured off as far as possible and the remainder adhering to the solid sulphide of lead was separated by distillation at a moderately high temperature and the whole fluid product thus obtained was submitted to distil-lation. The first product passing over was the excess of bisnl-phide used after which the temperature of the boiling liquid gradually rose when some acetic acid with a trace of acetone made its appearance till the temperature gradually rose to 13'i°C.and remained constant till the whole had passed over. The portions of distillate collected near the latter temperature had a pungent acid odour attacking the eyes and nostrils; when mixed with water it sank and gradually dissolved with rise of temperahre. On mixing it with alcohol the odour of acetic ether was produced. To decide the matter an analysis was made of the portions which boiled at 137". 0-3010 grm. burnt with oxide of copper and oxygen gave 05170 of CO, and 0.1636 of water. Calculated. Found. c* 48 47-05 46.84 H6 6 5.88 6-03 03 48 47-07 I 102 100.00 BROUGHTON ON A NEW BEACTION FOR THE The liquid was therefore acetic anhydride and its production can be expressed by the equation- 2 r2%$!Io 1+ CS = 2PbS + C02 + 2 [c21E-I,o01 C2H30} L C2 H3O}o Experiments with acetate of silver gave a similar result with even greater readiness.The above reaction of bisulphide of carbon it will be perceived is susceptible of at least three important applications for the for-mation of organic bodies if it prove to be ill any respect a general one. 1. The production of anhydrides as above from metallic salts. 2. The formation of compound ethers by allowing the anhy- drides in the nascent state to react on an alcohol. 3. In certain cases for the isolation of anhydrides of electro-positive radicles or ethers.For the second application it was proposed to produce an ether of acetic acid which had not hitherto been successfuliy prepared and for this purpose acetate of phenyl was chosen. This sub-stance Scrugham (Chem. SOC.Qu. J. vii. 241) attempted to procure by acting on acetate of potash with an alcoholic solution of phosphate of phenyl but did not succeed in obtaining it pure. Berthelot had found during his experiments on etherification that a small percentage of acetic acid entered into combination with phenylic alcohol when heated with the latter in sealed tubes. In order to procure this ether acetate of lead was at first sealed up with an equivalent quantity of pheriylic alcohol and an excess of bisulphide of carbon ; but after some experiments it was found better to operate with only half an equivalent of phenylic alcohol as the presence of some of the latter in an uncombined state seriously affected the eventual separation of' the acetate in a state of purity.The following was therefore the metJhod adopted :-20 grammes of well-dried and finely-divided acetate of lead was sealed up in strong tubes with 3 granimes of phenylic alcohol and a considerable escess of bisulphide and heated in an oil-bath to about 170°C. The reaction soon commenced and proceeded with more regularity than in the preparation of the anhydride since the lead- salt is soluble in the alcohol so that the bisulphide is enabled to act with greater readiness. It was found necessary to open the tube daily for it was shown by some explosions that the pressure PRODUCTION OF ANHYDR1I)ES AND ETHERS.of the liberated gas was very high. When the action had ceased the liquid products were separated as above described and re-distilled. After the excess of bisulphide had distilled acetic acid in considerable quantity passed into the receiver then a small quantity of acetic anhydride after which the temperature rose rapidly to 190"C. when a liquid of a pleasant empyreumatic odour made its appearance and when the temperature had attained 310" C. the whole had passed over. The portions distilling above 190' were rectified and by re-peated fractioning the greater part was obtained of a constant boiling point of 200". This was submitted to analysis as follows by combustion with oxide of copper and oxygen :-I.0.2142 gramrnes gave .5554 GO and *1133H,O. 11. 0.1964 grammes gave -5098 CO and -1060 H,O. Calculated. r. II. c 96 70.59 707 I 70.78 * * 5-88 5.87 5.99 0 32 23.53 -136 100.00 The vapour-density of the liquid was taken as follows by Gay Lussac's method wing a bath of spermaceti :-Weight of liquid employed 0.2299 grm. Observed volume of vapour 70.128 cc. Temperature 1218"C. Height of barometer 744.5 mm. Difference of heights of internal and external mercury 32 mm. Height of column of spermaceti 230 rnm. at 45'. These data give sp. gr. of vapour 4-72 The calculated density of acetate of phenyl is 4-59. The liquid therefore was acetate of phenyl. Acetate of phenyl is a colourlesv liquid boiling at 2OO0C.,of a peculiar and fragrant odour which is very persistent; its sp.gr is 1.074 being somewhat heavier than phenylic alcohol as acetic ether is heavier than ordinary alcohol. Though quite colourtess when freshly distilled it becomes somewhat yellow by keeping. It is slightly soluble in water in which it sinks and to which it imparts its peculiar odour. It is neutral to test-paper and is not decomposed by boiling water ; even when heated with water to 180" BROUOHTON ON ANHYDRIDES AND ETHERS. it acquires but a very slight acid reaction. Boiling solutions of the fixed alkalis gradually dissolve acetate of phenyl with formation of an alkaline acetate and phenate. Its index of refraction is the same as that of German fusible glass on which account tubes of the latter become invisible when immersed in this ether.It will appear from the above experiments that this reaction of bisulphide of carbon will most probably be found of service in isolating anhydrous acids in cases where the ordinary methods are riot convenient and will also it is believed receive many applica-tions as a general mode of preparing compound ethers since it has the advantage of being applicable to small quantities. Phe-nylic alcohol which has hitherto been found so difficult of etheri-fication may probably by the above process yield its full complement of ethers in the manner of alcohols of other series. Experiments have been commenced to illustrate the third application of this reaction namely that of eliminating phenylic ether from phenate of lead.Whether the method be applicable as a means of procuring double ethers and anhydrides further experiment must show. In conclusion the following desiiltory qualitative experiments have been tried :-Chloride bromide iodide and fluoride of lead are not attacked by bisulphide of carbon. Nitrate of silver is most readily acted on by bisulphide of carbon with production in addition to sulphide of silver of a green liquid and a white solid substance ; but on attempting to open the tubes they have burst with a most violent explosion. Sulphate of lead is not affected by sulphide of carbon. Benzoate succinate and ferrocyanide of lead are readily acted on by the bisulphide. Formate of lead is entirely converted into sulyhide by bisulphide of carbon with much evolution of gas; traces of a strong acid are evolved together with a sulphur-compound of a powerful odour ; all attempts to obtain formic anhydride have been unsuccessful the latter being apparently entirely decomposed into gases.Oxalate of lead is entirely unaffected by sulphide of carbon at a high temperature. I take this opportunity of expressing my thanks to Professor Frankland for opportunity and leisure to make the above experi- ments.