Citronella

Present in citronella and valerian oils, tur penline, ginger, rosemary and spike oils. It is produced artificially by the elimination of hydrogen chloride from bornyl chloride (artifi cial camphor) or from isobornyl chloride, by the dehydrogenation of borneol and isobor-neol and by the action of elhanoic anhydride on bornylamine. Chiral. 

ELEMICIN In varying amounts in citronella, elemi, mace, nutmeg, parsley snakeroot and tarragon. 

Citronellal occurs naturally as the principal component of citronella oil and is used as an insect repellent... 

Semmler and Spornitz have isolated a sesquiterpene from Java citronella oil, which they have named sesquicitronellene. It has the following characters —... 

Ceylon citronella oil contains an olefinic sesquiterpene having the following characters -—... 

Geraniol, Cj(,Hj-OH, is a constituent of many essential oils, both in the free state and in the form of esters. It is present to a very large extent in palmarosa oil, ginger-grass oil, and citronella oil, principally in the free state, and in geranium oil, to some extent in the free state, but principally in the form of esters. It is also an important constituent of otto of rose, and is present in numerous other oils belonging to the most distantly related groups. 

Harries and Comberg have also supplied much evidence, which, taken with the above-mentioned researches, places the chemical isomerism of citronellol and rhodinol practically beyond dispute. By ozonisation experiments decomposition products were obtained, which proved that natural citronellal, obtained from citronella oil, is a mixture of about... 

H. J. Prins has now isolated the two isomeric citronellals from Java citronella oil (see under citronellal). 

Some oils consist almost entirely of esters for example, those of Oaultheria procumhens and Betula lenta contain about 99 per cent, of methyl salicylate. Bergamot and lavender owe the greater part of their perfume value to esters of linalol, of which the acetate predominates. Geranium oil owes its fragrance chiefly to geranyl esters, of which the tiglate is the chief. On the other hand, oils such as spike lavender, sandalwood, lemon-grass, and citronella contain but small quantities of esters, and owe their perfume value to entirely different types of compounds. 

Citronellal which was originally termed citronellone, is one of the characteristic constituents of citronella oil, in which it occurs to a considerable extent. It can be prepared by shaking the essential oil with a hot solution of sodium bisulphite, and decomposing the resulting bisulphite compound by means of sodium carbonate and distilling the citronellal in a current of steam. Citronellal is optically active, and it is probable that the specimens isolated from natural sources are mixtures of the two optically active isomers, so that the actual theoretical rotation is not known with certainty. 

Citronellal prepared from Java citronella oil is laevo-rotatory to the extent of about - 3°. 

CitroneUal and geraniol occur together in citronella oils, and several. methods have been proposed for the estimation of these two constituents. The results are only approximate in each case. These are as follows —... 

One gram of Ceylon citronella oil or 0 5 grams of Java citronella oil is mixed with 10 c.c. of a freshly prepared 2 per cent, alcoholic solution of redistilled phenylhydrazine and allowed to stand for one to one and a half hours in a flask of about 50 c.c. capacity closed with a glass stopper. Twenty c.c. of decinormal hydrochloric acid is then added, thoroughly... 

Terpenes are commonly employed for diluting lemon, orange, and bergamot oils. The addition lowers the specific gravity, increases the optical rotation, and lowers the proportion of oxygenated constituents. Terpinolene, a by-product in the manufacture of terpineol, has been detected in some oils, notably citronella and spike, lavender. It can be detected by its odour in the fractionated oils. 

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