

The Cyclic (Aromatic) Aldehydes occurring in 



Eucalyptus Oils 



Cuminal C 10 H,.,O. Aromadendral Ci H 14 O. Cryptal C 10 H 16 O. and Another. 



( >\i or more members oi this very interesting group oi itic aldehydes oi i ur 



in the oils distilled from the members of the typical " Box " group E. hemiphloia, 

 &c. and chemically related " Mallees " E. polybractea, &c. . as well as from 

 other closely associated Eui alj p1 



rhese aldehydes do not seem to occur in the oils oi the earlier memb< 

 oi the genus the pinene \ ielding group , nor in those oi the more re enl species, 

 particularly those in which phellandrene is the more pronounced terpene. In 

 these latter species the characteristic constituent is the ketone piperitone. 



It thus appears that they are common to a large proportion oi the oils "I 

 dyptus species occupying the middle portion in the evolutionary sequence oi 

 the genus groups I V and V . and they are so shown grouped together in the 

 evolutionary table elaborated in this work. 



It may also be stated as a general rule that cymene is present in either 

 larger or smaller amount in the oils of species containing these aldehydes, and we 

 have isolated tins hydrocarbon from many of the oils of this class, and proved 

 its identity chemically. 



When the members of this aldehydic group are pronounced, at least two 

 and sometimes three or them occur together, particularly at certain periods of 

 the year ; at other times the cuminal is practically absent, and it is probablv due 

 to this peculiarity that the conclusions of previous investigators have not been 

 altogether in agreement. The presence of cuminal in the oils of certain 

 Eucalvpts was noticed many years ago. 



Some members of the " Box " group yield an oil in which the terpene 

 phellandrene can be detected at certain periods of the year, although absent at 

 other times !■'.. hemiphloia for instance), and this has often been observed with 

 species which are on the border line, as it were, of phellandrene production. One 

 peculiaritv which has been noticed is that when phellandrene can be readilv 

 detected in these oils, cuminal is present in greatest amount ; and it was fortunate 

 that in the work originally carried out on these alhehydes from the oil of 

 E. hemiphloia, lor the first edition of this work, the material was d'stilled at the 

 time of the year when phellandrene could not be detected, and cuminal absent 

 or only present in very small amount, consequently the aldehyde regenerated 

 from tin- crystallised sulphite compound was at that time almost entirely 

 aromadendral. 



I his diminution in the amount of cuminal, and the deficiency in 

 phellandrene, is probably responsible to a certain extent for the formation oi the 

 dihydro- and tetrahydro< uminals, which can then be isolated from these oils. 



Wallach has shown [Ann. 340 (1905) 12] that the oxidation of 

 /8-phellandrene produces a glycol, which on treating with dilute sulphuric acid 

 gives dihydro- and tetrahydrocuminaldehydes. Molecular re-arrangement of a 

 somewhat similar character ma\ perhaps take place naturally under climatic 

 condition-, ami the seasons' changes. 



* In the lir-.t edition of this work, the optical peculiar to the oil oi certain Euca 



red to be a single substance and named aromadendral. I hi name i n tained in Un> editio ote the 



occurrence of one oi i o bers of this group of aldehydi 



