RR a a ee i a te By ine ¢ Mina re rae ETE a te Mee ea 
114. “ REPORT OF SCHIMMEL 8 
(the authors here certainly do not mean turpentine, but oil of trp 
from 25 to 35 per cent. of isoprene. OE 
Mixtures of benzene and French oil of turpentine were decomposed i in 1 An 
- isoprene lamp, when the yields were as follows: — 
pure oil of turpentine . . . 14.6 per cent. of isoprene — Sine Bee 
95 per cent. of turpentine oil ies S per cent. of benzene: 18.85. Hdl: id. as percentage st i : 
8 id. id. ee oh id. —: 19.8 id. id. of the oil %, 
fo id. id. S28 Mid: i BAB ids ends of turpentine 
50 id. rr epee! SG oeeck tc id. y 306°< id. id. used, <seae 
The highest yield of isoprene is obtained if the oil of turpentine is not heated — 2 
before the pyrogenation, by spraying it or dipentene e.g. into the space heated to 500 ~~ 
or 600°. Natural myrcene yields on pyrogenation from 60 to 70 per cent. of isoprene. 
Some time ago, A. W. Schorger') discovered that the turpentine oil from Pinus 2 
ponderosa, Laws., chiefly consists of 6-pinene. As, according to the German Patent 200934 
(U. St. Am. P. 1057680) considerably higher yields of isoprene are supposed to be : 
obtained from #-pinene than from «-pinene, Schorger and R. Sayre®) heated ordinary 
oil of turpentine as well as the variety from Pinus ponderosa in Harries’ isoprene lamp*). 
In either case, the principal constituents of the oils (#- and 6-pinene) had been © 
increased as far as possible by rectification. No great difference was observed; the yield 
of isoprene amounted to 8.1 to 10.3 per cent. for oil of turpentine and to 9.4 per cent. ~ 
for 6-pinene from the oil of turpentine from Pinus ponderosa. The authors explain the — 
formation of isoprene by an intermediary formation of dipentene according to the 
scheme: pinene — dipentene > isoprene. In their opinion, the technical use of this 
reaction for obtaining isoprene would not pay, but as dipentene affords a good yield 
of isoprene it would be interesting to work out an easy method of converting pinene 
into dipentene. 
The isoprene lamp used by the authors differs somewhat from that described by — 
Harries. Its construction may be clearly understood from the illustration accompanying © 
the treatise. 
&-Myrcene. On heating isoprene for 3 to 5 days up to 80 or 90° in a sealed © 
tube, as I. Ostromysslenski and F. Koschelew*) discovered, a myrcene-like hydrocarbon 
is formed, for which they give the formula CHy: CH: C(CHs): CH: CH2-C(CHs) : CH: and 
which they call 6-myrcene. B. p. 63 to 63.5° (20 mm.); 58° (13 mm.). It is a colour- ~ 
less, readily mobile liquid of myrcene-like smell that irritates the mucous membranes ~ 
of the nose. The action of sulphuric acid leads, after 2 to 5 days, to an amorphous ~ 
product. When heated with sodium and benzoyl peroxide, or when acted upon by © 
sodium and barium peroxide, 6-myrcene is transformed into isoprene caoutchouc. | 
6-Myrcene is to be considered as an intermediate product of the polymerization of s 
isoprene to caoutchouc. The endeavours to prepare @-myrcene by dehydration of “ 
terpene alcohols, such as geraniol, linalool, &c., gave no result. — 
The polymerization of 6-myrcene is perhaps the only synthesis of natural caoutchougs ee 
The identity of the caoutchouc from #-myrcene with the natural Para caoutchouc is © 
shown by the position of the elasticity point and fatal temperature; besides, the tem-_ a 
perature curves for viscosity, surface tension and density are analogous for both kin 35) 
of caoutchouc. It may be presumed that the synthesis of caoutchouc in tropical plan iS 
passes likewise through the stage of S-myrcene or myrcene-like hydrocarbons. 
1) See Report April 1913, 101. — *) Journ. Ind. Eng. Chemistry 7 (1915), 924. — 3) See Report Oc 
1911, 127. — *) Journ. russ. phys. chem. Ges. 47 (1915), 1928, 1941; Chem. Zentralbl. 1916, 1. 1068, 1136 
