SOME INVESTIGATIONS OF THE CHEMISTRY OF CARENE 263 ($41 (35) (36) CH• ($7) ($8) ($9) 2-ene. Indeed, car-3-ene (formula 2) may be considered to have quasi- aromatic character the bonds allylic to the double bond are in fact quasi-vinylic with respect to the three membered ring. Hence under the conditions of pyrolysis and flow-rate that we employed, the high temper- ature necessary to effect cracking of (+)-car-3-ene militated against the formation of acyclic products. Indeed we found that at these temperatures both It- pinene and myrcene afford aromatic products. 7 6 2 5 3 10 10 9 (401 (41) (42) ? Cracking of (+)-car-3-ene started at a lower temperature (300øC) when the column was packed with a potassium aluminosilicate catalyst. At 400øC it was completely transformed giving m- cymene (8.2%), p-cymene (10.9%), a- terpinene (formula 40) (21%), (+)-p-mentha-2,4(8)-diene (formula 41 R, CH 3) (14%) and m-mentha-1, 3(8)-diene (formula 42) (34)

264 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS