- 69 - 



which occasional allusions have been made in previous reports 1 ). It 

 will therefore only be necessary to mention here, for the purpose of 

 completing the record, the results which have been obtained since 

 we last dealt with the matter in our Reports. 



As already discovered by us, hyssop oil contains, in addition to 

 /?-pinene, an active ketone, 1-pinocamphone, which had hitherto not 

 been observed in essential oils. Its oxidation with permanganate 

 resulted in active 1-pinonic acid. Notwithstanding that after our 

 experiments in its decomposition we had no doubt as to the char- 

 acter of this ketonic acid from pinocamphone, yet we were unable to 

 give absolute proof of the correctness of our view, because Tiemann 

 had obtained, by dry distillation of a-dihydroxydihydro campholenic acid, 

 an acid C 10 H 16 O 3 , which he regarded as 1-pinonic acid, and which 

 possessed quite different properties. We therefore set ourselves the 

 task of preparing the optical antipode of the acid which we had ob- 

 tained, in order that by combining the two active varieties we might 

 arrive at the well-known racemic pinonic acid. 



Among the available data concerning the oxidation of pinene, 

 particulars as to the rotation of the turpentine oil fractions employed 

 are unfortunately almost wanting. The principal product obtained 

 from them was always racemic pinonic acid. We proceeded from 

 the assumption (which was confirmed by the experiment) that it must 

 be possible, by using pinene of high rotatory power, to obtain the 

 active acid as the principal constituent. For this purpose we employed 

 d-pinene from Greek oil of turpentine, with the following properties : — 

 b. p. 156 (760 mm.), d 15 o 0,8642, « D +40,23°, n D20O 1,46565. The 

 specific rotation [«]© -f- 46,73° which was calculated from the above 

 is the highest value which has thus far been observed for d-pinene. 

 By oxidising with permanganate the active d- pinonic acid was obtained 

 in the form of a viscous yellow oil, b. p. 168° (12 mm.), «d -{-27°. 

 The acid soon solidified. M. p. 68 to 69°, [«]d -f~ 88,27° in a 

 5,647 per cent, chloroform solution. The properties of the derivatives 

 conformed completely to those of the laevorotatory acid. The semi- 

 carbazone melted at 204°, the oxime at 129° and the d-metho-ethyl 

 heptanonolide, which was formed by rearrangement with sulphuric 

 acid, at 47 to 48°. Mixing of equal quantities of the two optically 

 isomeric acids led to the well-known racemic pinonic acid (a-pinonic 

 acid) of which the m. p. was found to be 103 to 104 . By uniting 

 the two active oximes melting at 129° there was formed the racemic 

 oxime, m. p. 150°, while mixture of the two ketolactones produced 

 racemic metho- ethyl heptanonolide, m. p. 63 to 63,5°, a substance 

 which has long been known. These experiments conclusively show 



x ) Report April 1908, 59; April 1909, 120. 



