152 HEPORT— 1900. 



A mixture of the ft- and y-esters is readily obtained by adding an 

 ethereal solution of iodine to the sodium derivative of ethyl benzoyl- 

 acetate, obtained by the action of metallic sodium on an ethereal solution 

 of the ester. The two ketonic esters are readily separated from one 

 another by fractional crystallisation. When either of them is treated 

 with sodium methoxide, a yellow crystalline meal, consisting of the 

 sodium derivative of the a-ester, is obtained. The aqueous solution of 

 this substance, when treated with excess of dilute sulphuric acid at the 

 freezing temperature, yields the o-ester, which separates as a thick oil 

 possessing the colour of chlorine gas. The /tester, which was first 

 described by von Baeyer and Perkin,' melts at 128-130°, the y-ester at 

 75°, and the former is less soluble than the latter in most solvents. Both 

 esters are optically inactive, the p-ester by external, the y-ester by 

 internal compensation. The ketonic esters are neutral to litmus, and 

 practically insoluble in cold dilute alkalis. In their chemical properties 

 they are exactly alike. 



The a-ester differs, both in physical and chemical properties, from 

 the ketonic esters. It is an oily liquid, has a strongly acid reaction, 

 and dissolves in cold dilute alkalis. It gives a characteristic dirty brown 

 coloration with ferric chloride, which is not shown by the ketonic 

 esters, and moreover is unstable, gradually passing into a mixture of 

 the ft- and y-esters at the ordinary temperature, the change taking place 

 quickly at 130°. 



f the view put forward by Knorr as to the relation of the three esters 

 to one another is correct, the ft- and y-esters should give very similar, 

 if not identical, absorption curves, since stereo-isomerides which differ 

 only in the configuration of their asymmetric carbon atoms so far as they 

 have been investigated in essential oils and their hydrocarbons, are not 

 found to differ either in the amount or the character of their absorption. 

 The a-ester, on the other hand, having a different constitution, should 

 exhibit a distinct series of absorption spectra. 



We have photographed and measured the spectra of alcoholic solu- 

 tions of the three substances, and the results obtained entirely bear out 

 the conclusions arrived at by Knorr on purely chemical grounds. The 

 spectra of the ketonic esters are identical. The amount of absorption is 

 considerable, all rays beyond ^/X 2795 being cut off by a layer 25 mm. 

 thick of a solution containing 1 milligram-mol. in 100 c.c. of alcohol. 

 There is also a well-marked band of selective absorption reaching from 

 ^/\ 3824 to ^ /\ 4306 in a layer 3 mm. thick of a solution containing 

 1 milligram-mol. of the ester in 2500 c.c. of alcohol. This band is very 

 persistent, and is still distinctly marked in a layer 4 mm. thick of a solu- 

 tion containing only 1 milligram-mol. in 12,500 c.c. of alcohol. 



The spectrum of the «- or enolic form is quite different from that 

 of the ketonic esters. The general absorption is greater, a layer 25 mm. 

 thick of a solution containing 1 milligram-mol. in 100 c.c. of alcohol 

 cutting off all rays beyond ^/\ 2171. The absorption band of the 

 ketonic esters is altogether absent, whilst a well-marked band makes its 

 appearance in a layer 5 mm. thick of a solution containing 1 milli- 

 gram-mol. in 500 c.c. of alcohol between V\ 2546 and i/X 3148. This 

 band quickly dies out, no trace of it being visible in a layer 4 mm. thick 

 of a solution containing 1 milligram-mol. in 500 c.c. of alcohol. 



' Ber. 1884, 17, 60. 



