August 30, 1912] 



SCIENCE 



261 



which, while it may have some objections, 

 has at the same time decided advantages 

 over the starch or reduction theory. 



It is common knowledge that the ter- 

 penes, when exposed to air, slowly change 

 to complex polymers and resins of un- 

 known composition. The principle in- 

 volved is doubtless condensation followed 

 by oxidation. Wohler was the first to sug- 

 gest that the resins may be built from the 

 terpenes by the above-mentioned condensa- 

 tion and oxidation process. He based his 

 assumption on the well-known fact that 

 turpentine absorbs oxygen, forming a resin. 

 This oxidation process may be represented 

 by the following equation : 



2Ci„H„ -t- 30 = C.„H3„0^ -1- H.O. 



"Wohler, unfortunately, presented no ex- 

 perimental data. Later, Cailliots obtained 

 a resin by the oxidation of turpentine with 

 nitric acid. It was not well defined, how- 

 ever, and not identical with any of the 

 common resins, although it bore some sem- 

 blance of common pine resin. 



Barth^ obtained, by oxidizing oil of lav- 

 ender, a terpene, an amorphous resin which 

 he carefully studied and gave the formula 

 C20H30O3, apparently an oxyabietic acid. 



Heldt,* in an exhaustive study of the 

 resins, produced common sylvic acid by 

 oxidizing a polymerized form of turpentine 

 according to the following equation : 



2(CioH„) or a„Hj2 4- Oj = Ca,H320;, sylvic acid, 

 and 



CmHs^Oj + O = a„H3„0a -f H2O, or abietie acid. 



This work has been repeated, but without 

 obtaining either sylvic or abietie acids. 



One of the most interesting communica- 

 tions along this line was presented by 

 Bruylaut. He obtained, by a method not 

 given, a polymer of pinene which he repre- 



'Ann., 143-313. 

 •Ann., 63-48. 



sented as a condensation of two molecules 

 of pinene or dipinene. By oxidizing this 

 substance he obtained an acid which had 

 the empirical formula for abietie acid: 



CeHe< 



C3H, 



C„He< 



C3HJO2 



No details of the work, however, were 

 given. 



Work on the condensation of the ter- 

 penes has been in progress at the Univer- 

 sity of Minnesota for several years. Before 

 describing some of these experiments, how- 

 ever, it may be of interest to briefly trace 

 the work on the synthesis of the terpenes 

 themselves. It was observed early in this 

 work that when pinacone is treated with 

 bromine, an extremely complex reaction 

 takes place and among the products formed 

 are isopropyl alcohol and substances be- 

 longing to the terpenes. It was found, 

 however, on carefully studying the reac- 

 tion, that Baeyer had already observed this 

 fact, but had not followed out the reaction, 

 doubtless on account of the extreme com- 

 plexity of the reaction. If, however, we 

 take into consideration these two sub- 

 stances, the reaction may be represented as 

 follows : 



6C„H„02 = 2C3HsO -t- 3CioH,<, -|- lOH^O. 



Some time previous to this work, Konda- 

 kow^ in his work on angelic and tiglie acids 

 obtained from them a hydrocarbon which 

 proved to be a methyl derivative of cro- 

 tonylene. It had the general formula for 

 the hemiterpenes. From the description it 

 seems quite likely that this hydrocarbon is 

 related to the terpenes, for it has the for- 

 mula CH3=C(CH3)— CH=CH2, which is 



' Jour, of the Euss. Phys. Chem. Soc, 1891, I., 

 178. 



