J><5 -Appendix. 



Oil of turpentine and its numerous isomers have mostly 

 been placed, unclassified, among " the vegetable substances little 

 known," but there is a beginning that promises to draw them 

 into the aromatic group and assign them graphical formulae of 

 the the hexagonal type. In 1872, A. Oppenheim reported to 

 the German Chemical Society an investigation at the Berlin 

 Laboratory 4 on the production of a cymene from oil of turpen- 

 tine by abstraction of hydrogen (cymene dibromide being heated 

 with anilin). As a result of his research the investigator gives 

 this graphical formula for turpentine oil : Here one of the carbon 

 (CH 8 ) atoms of the ring has been loosened 



| and displaced by the triad CH, giving 



the adjacent carbon atom only one line 

 // ^ of connection in the ring and two out- 



H C C H s ^e bonds, so that four carbon atoms 



I II carry five of hydrogen. The remain - 



TT __A p rr 



ing two points of the hexagon have 



\ / taken methyl (CH 3 ) instead of hydro- 



(CH) gen and one of these methyl molecules 



has methyl again substituted for two of 



H 3 ) (C H 3 itg hydrogen atoms< Laterj Oppen- 



heim reports the formation of cymene from the terpene of cum- 

 min oil 5 and offers other confirmations. Kekule has since 

 traced relations between cymene and camphor (the immediate 

 oxidate of a terpene), C 10 H 16 O, from which he presents a 

 graphical formula. Kekule confirms the relationship between 

 cymene and the terpenes, using iodine instead of bromine, and 

 accepts Oppenheim's conclusions. 6 



Graebe has dissented from the view that turpentine oil is of 

 the aromatic type, although he finds a relation between the ter- 

 pene in wormseed oil and cymene. 7 The conclusions of Oppen- 

 heim are mostly confirmed and extended by the labors of C. R. A. 



(4) Berichte der deutschen cJiemischen Gesellschaft, V., 94. 



(5) Berichte d. d. chem. Gesell., v, 628 ; vi., 915. 



(6) Bericht. d. deut. chem. Gesell., vi., 437: Jour. Chem. Soc., 1873, 889. 



(7) Deut. chem. Ges. Ber. t v., 677. 



