studies in essential oils

Abstract

The thesis consists of three parts. The first part deals with the synthesis of three alkyl azulenes. The second part deals with the analysis of the essential oil from the roots of Aristolochia indica. The third part deals with the investigations on the essential oil from the wood of Lansium annamalayanum Bedd.

Chapter I The objective of synthesising the alkyl azulenes is described. Methods of purification and identification of azulenes are also outlined. The versatility of the diazoacetic ester method in the synthesis of alkyl azulenes, along with some of its limitations, is briefly discussed. Some of the other methods of azulene synthesis are also mentioned.

Chapter II This chapter deals with the synthesis of 6 ethyl azulene. 5 Ethylindane has been obtained by the Clemmensen reduction of 5 acetylindane. Starting from this indane, 5 ethyl azulene has been prepared by the diazoacetic ester method.

Chapter III This chapter deals with the synthesis of 2 methyl 5 ethyl azulene. 2 Methylindane has been acetylated to give 2 methyl 5 acetylindane. From this, 2 methyl 5 ethylindane has been obtained through Clemmensen reduction. This indane is then converted to 2 methyl 5 ethyl azulene by the diazoacetic ester method.

Chapter IV This chapter deals with the synthesis of 1 ethyl azulene by the diazoacetic ester method, starting from 1 ethylindane. All the above azulenes have been characterised as S trinitrobenzene adducts.

PART II Chapter I This introductory chapter deals with the application of infra red and ultra violet spectroscopy in the study of some essential oil constituents. The chemistry of certain azulenic sesquiterpenes, sesquiterpene alcohols and sesquiterpene oxides is also described. The roots of Aristolochia indica on steam distillation yield an essential oil (0.6%). The analytical constants of the essential oil are given. The essential oil has been fractionated at 2 mm:

5% of the oil distils below 87°C/2 mm 5% of the oil distils at 87-105°C/2 mm and consists of sesquiterpenes 24% of the oil distils at 105-160°C/2 mm The residue is 1%

The sesquiterpene portion consists of two sesquiterpenes: sesquiterpene A and sesquiterpene B. The work done on sesquiterpene B is described. From the higher boiling fractions, a crystalline solid (m.p. 103-104°C) has been isolated and identified as ledol.

Chapter III This chapter deals with the work done to elucidate the structure of sesquiterpene A. The structure proposed is based chiefly on the results of sulphur dehydrogenation and ozonisation of sesquiterpene A and its dihydro derivative.

PART III Chapter I The wood of Lansium annamalayanum Bedd. on steam distillation yields an essential oil (2.3%). The essential oil consists chiefly of a new sesquiterpene, chigadmarene, along with bisabolene.

Both chapters of Part III formed part of my thesis for which I was awarded the Associateship of the Indian Institute of Science (A.I.I.Sc.) in 1961.

Chapter II This chapter deals with the elucidation of the structure of chigadmarene. The structure is based chiefly on the infra red absorption spectrum of the hydrocarbon, and the results of dehydrogenation and ozonolysis.