TEEPBNES AND ESSENTIAL OILS, I. 51 



to assume that a minute trace of the metlij'lene derivative is always 

 -present. However that may be, it is a fact that all substances capable 

 of assuming the enol and keto types respectively act with the Grignard 

 reagent so far as they have been studied, as if composed of the former, 

 thus, acetoacetic ester, urea, thiourea and the amides, etc., all behave 

 toward alkjd magnesium halides as if they contained hydroxyl groups. 



EXPEEIIIENTAL. 



The action upon magnesium of limonene hydrochloride dissolved in 

 absolute ether, is not vigorous, or even fairly complete unless certain rigid 

 conditions are met, but if these are adhered to the reaction takes place 

 smoothly and very rapidly to practical completion. Many experiments 

 were undertaken to obtain the best conditions. The limonene hydro- 

 chloride must be as pure as possible and in most of my experiments it was 

 twice refraetioned in vacuo; the ether also must be very pure and ab- 

 solutely dry. The best results were obtained by the usual procedure of 

 removing all soluble impurities by shaking with small portions of water, 

 then drying the reagent over calcium chloride, distilling from sodium wire 

 and finally keeping tlie ether over sodium wire in a bottle protected by 

 a tul^e filled with soda lime. The Grignard body which is produced 

 absorbs oxygen very rapidly, and so in most instances my reactions were 

 conducted in an atmosphere of dry hydrogen. It is desirable to have the 

 magnesium as pure as possible, although satisfactory results may be ob- 

 tained with magnesium which is not strictly so if it is properly treated 

 beforehand. The persistency with which limonene hydrochloride refuses 

 to react iinless all conditions are strictl}^ met is shown by one exjseriment 

 in whi'eh a mixture of limonene h3Tlrocliloride, magnesium and ether was 

 placed at ordinary temperature without reaction and finally heated in 

 a sealed tube to 120° to 130° for twenty hours without any change. 



The following experiments gave a difl^erent result : 



Experiment 1. — The limonene was obtained fi'om orange peel oil which was 

 twice refraetioned and the terpene then distilled over sodium; its boiling point 



was 174° to 176° at atmospheric pressure. Specific gravity, ~=0.8350: N^ 

 = 1.4670; A_^_j]^o.7. One hundred and fifty grams of this product were 



dissolved in an equal volume of dry carbon bisulphide and dry hydrogen chloride 

 was passed for two working days into the liquid, which was kept in a freezing 

 mixture. The product was then washed with water and dilute alkali, dried over 

 calcium chloride, the carbon bisulphide distilled and the product fractioned in 

 vacuo. One hundred and ten grams of limonene hydrochloride of a boiling point 



of 105° to 107° at 20 millimeters were obtained. Specific gravity, ^=0.9703; 



30° 30° 



N^=--=1.4770; A— — = 73.1°. The following was the analysis: 



Found Calculated for CioHi,Cl 



(percent). (percent). 



CI 20.1 20.3 



