— 133 — 



instead of, as he calculates, -[~ I °4° I 5 / — IOI ° 3 o/ = + 2 ° 45^ it 



should be pointed out that the mixture of two components whose 



rotatory powers are not equally strong, gives the arithmetic mean, in 



+ I04°i5'— ioi°30 / , o / i u- u 



this case — -4-i° 22,5 , — a value which corre- 



2 



sponds well with the value found. 



Sabinene. With regard to the relationship of sabinene towards 

 terpinene, see under terpinene, p. 137. 



Thujene. For the relations between thujene and terpinene, see 

 under terpinene, p. 138. 



Terpinene. On the subject of terpinene and its derivatives, and 

 also on its relationship towards sabinene and thujene, we have before 

 us several treatises by Wallach and by Semmler, on which we report 

 in a connected form as follows. 



In the course of the last few years we have repeatedly had occasion 

 to discuss 1 ) works on the chemical behaviour of terpinene, but only 

 the last work of Wallach 2 ) on this important hydrocarbon brings 

 the results hitherto obtained more or less to a conclusion. The only 

 derivative characteristic for terpinene w r as the nitrosite C 10 H 16 N 2 O 3 

 (m. p. 1 55 ); on the other hand, very little was known with regard 

 to the hydrohalogen addition products. These now Wallach has 

 examined again, and he has thereby come to the result that terpinene 

 yields crystallised halogen derivatives which are very similar to those 

 of dipentene, and can easily be mistaken for the latter. They also 

 occur in cis- and trans-form, and even if they have been produced 

 from active material they are optically inactive. A comparative review 

 of the melting points of the trans-forms of the terpinene and 

 dipentene series is given below: — 





from terpinene 



from dipentene 



C10 H 16 • 2 H CI 



51 to 52 



49 to 50 



C10 H 16 • 2 H Br 



58 to 59° 



64 



CioH 16 • 2 HI 



7 6° 



77 and 78 to 79 



C 10 H 18( OH )2 



135 to 136 



156° 



As a result of his experiments, Wallach proposes as crude material 

 for the trans-terpinene compounds, sabinene and the terpineol of oil 

 of sweet marjoram (see p. 135). But the hydrohalogen compounds, for 



*) Report April 1901, 67; October 1901, 61; April 1902, 88; October 1905, 

 100; April 1906, 115. 



2 ) Liebigfs Annalen 350 (1906), 141. 



