530 H. G. SMITH. 
The molecular structures which have been suggested for 
terpinene are the following, known asa, 6, and y-terpinenes 
respectively:— 
C-CH, Cc: CH, C-CH, 
He ©) S CH H.C Vn py CH, H,C X CH 
| | 
H.C JCH HC CH, He CH 
6) C C 
O,H, C,H, C,H, 
Wallach*' contends that it has been shown with sufficient 
clearness that terpinene is a mixture of Ai,3. and A 4,4. 
dihydrocymenes, and that it is the former which gives the 
characteristic nitrosite reaction. A considerable amount 
of work has been undertaken upon this terpene by Wallach, 
Semmler, Auwers and others, and both the «, and y-forms 
have been synthesised during these investigations. 
As terpinene has not, so far, been regenerated from its 
solid derivative ina pure form, its physical properties can- 
not be stated with precision, but from the several results 
obtained with the terpene formed in various ways the 
following range of figures may be given:— 
Boiling point 171 to 181° C.; specific gravity 0°842 at 22° 
to 0°848 at 18°; refractive index 1°4719 to 1°4789. 
The two reactions which largely help to distinguish 
terpinene from other terpenes are (a) the crystallised 
nitrosite OioHisN2O3 melting at 155° C., which is formed 
when the oil is treated with nitrous acid, and (b), the com- 
parative ease with which it is destroyed when treated in 
the cold with Beckmann’s chromic acid mixture; this 
reagent under such conditions has little action upon either 
pinene, limonene or cineol. 
1 Ann. Chem., 374, 217. 
