394 



PREPARATION OF THYMOL FROM PIPERITONE. 



60 gram, piperitone were added to a solution of 175 gram, ferric chloride, 

 160 c.c. glacial acetic acid, and 500 c.c. water. The whole was then heated 

 on the sand bath to boiling. The action takes place according to the 

 equation 2 FeQ 3 + H 2 O = 2 FeCl 2 + 2 HC1 + O, and was completed at the 

 expiration of about one hour. The reaction product was then steam distilled, the 

 phenol separated and absorbed in a 5 per cent, solution of sodium hydrate, the 

 unabsorbed oil removed by ether, and the aqueous layer decomposed by 

 hydrochloric acid. The phenol was then distilled under reduced pressure, when 

 the thymol came over at 110-111 C. at 10 millimetres. In this way a 25 per 

 cent, yield of the weight of piperitone taken was recovered, but further researches 

 will no doubt result in a much better yield being obtained. The thymol 

 thus produced was identical in every way with the ordinary commercial article, 

 and gave the chemical reactions for that substance. 



QUALITATIVE AND QUANTITATIVE DETERMINATION OF PIPERITONE. 



The presence of piperitone can be determined somewhat readily in 

 Eucalyptus oils, as the crystalline compound formed when treated with sodium- 

 amalgam in ether-alcohol solution is quite characteristic. The crude oils of 

 some species, particularly that of E. dives, may be employed directly, but those 

 in which piperitone is only present in small amount should first be fractionated. 

 10 c.c. of the oil are added to twice the volume of a mixture of ether and 

 alcohol, or even 90 per cent, alcohol alone, and the necessary amount of 

 sodium amalgam added. After some time an insoluble crystalline product will 

 have formed if piperitone be present ; this can be filtered off, purified from 

 boiling alcohol, and the melting point determined. 



For quantitative determination the method of Burgess (Analyst, March, 

 1904) can be applied, as the reaction with piperitone goes quite smoothly, 

 using a 35 per cent, solution of neutral sodium sulphite. 5 c.c. of the oil are 

 introduced into a 200 c.c. flask, with the neck graduated in ^ of a c.c. The 

 sodium sulphite solution is then added, together with two or three drops of 

 ordinary phenolphthalein solution ; the flask is then placed in a boiling water 

 bath and thoroughly shaken. The red colour formed is neutralised with a 10 per 

 cent, solution of acetic acid, and the process repeated until the formation of the 

 red colour does not take place on further heating. The unabsorbed oil is then 

 lifted into the neck and read off when cold ; the difference between that amount 

 and the 5 c.c. taken gives the quantity absorbed, and this, multiplied by 20, 

 the percentage of piperitone. 



It is hardly likely that Eucalyptus oils other than that of E. dives will be 

 employed for the commercial production of piperitone, and as the fractionation 

 can be readily carried out, the commercial article should not contain less than 

 90 per cent, of that ketone. 



