126 



combination. The second racemic product had m. p. 48 to 50 . The 

 acid phthalic ester (m. p. 175 to 1 77°) could be split up into its active 

 component by fractionated crystallisation of the brucine salt. 



For the pharmacological behaviour of menthol, see p. 115. 



Terpineol. It is some time since Perkin 1 ) prepared an inactive 

 terpineol by treating the inactive 1 -methyl Z^-cyclohexene 4-carboxylic 

 ester with magnesium methyl iodide. An optically active zl 3 -p-menthenol-8 

 could likewise be obtained by the same method with the aid of inactive 

 1 -methyl A 3 -cyclohexene 4-carboxylic acid, which by fractional crystallis- 

 ation of the brucine and strychnine salts could easily be split up into 

 the optically active components 2 ). Recently 3 ), an easy method has 

 been found for the preparation of the above-named 1 -methyl zl 1 -cyclo- 

 hexene 4-carboxylic acid which also admitted of being readily split up 

 into the two optically active modifications. This method has been 

 used by Perkin, in collaboration with K. Fisher 4 ), for the synthesis 

 of the optically active terpineols. When subjected to the action of 

 magnesium methyl iodide, the esters yielded quantitatively the corre- 

 sponding active terpineols which melted at 35 precisely. The 

 specific optical rotation was found to be [«]p -|- 44,2° and — 46,6°, 

 whereas other authors had found higher values for this combination 5 ). 

 It was easy to obtain d-zl 3 > 8 ( 9 )-p-menthadiene from the above mentioned 

 d-zl 3 -p-menthenol-8 by the action of magnesium methyl iodide by the 

 cold process, but singularly enough a conversion of the active terpineols 

 into the corresponding limonenes under the same conditions was im- 

 possible, because almost complete racemisation supervened. The ab- 

 straction of water by means of anhydrous oxalic acid also resulted 

 only in almost pure dipentene. 



Terpinenol. In our last Report 6 ) we have referred briefly to 

 O. Wallach's synthesis of terpinenol- 1 , and we now extract the follow- 

 ing particulars from the more detailed account of the process which 

 has since appeared 7 ). 



z( 3 -Isopropyl cyclohexenone (b. p. 95 to 96 at 12 mm. pressure; 

 ^22° 0,944; n D22° 1*4817) was treated with magnesium methyl iodide. 

 The resulting alcohol (b. p. 92 to 97 at 14 mm. pressure; d24© 0,9210; 

 n D24° 1,4778; mol. refr. found 47,31, calculated 47,16) boiled at 



x ) Journ. chem. Soc. 85 (1904), 654; Report October 1904, 97. 



2 ) Journ. chem. Soc. 89 (1906), 839; Report October 1906, 107. 



3 ) Journ. chem. Soc. 93 (1908), 141 7. 



4 ) Ibidem 187 1. 



5 ) See Report April 1908, 186. 



6 ) Report November 1908, 180. 



f ) Liebig's Annalen 362 (1908), 279. 



