Citronellol determination

R,S)-Citronellal can be purchased from BASF, and (R)-citronellal from Dragoco, Fluka, or Takasgo Perfumery Co., Ltd., Japan. (R)-Citronellal can also be synthesized from pulegone with ee >99%.5 (S)-Citronellal may be obtained by oxidation of (S)-citronellol,6 which is accessible by different routes with ee 95%.7 The optical purity of citronellal can be determined by GLC after conversion to the acetal of (-)-(2R,4R)-pentanediol.8 For the reactions described, (R,S)-citronellal from BASF, (R)-citronellal from Dragoco, and (S)-citronellol from Fluka were used. (R,S)-Citronellal... 

Many essential oils contain esters (mostly acetates) of alcohols of the formulae C10HlsO (borneol, geraniol, terpineol, linalool), C H O (menthol, citronellol), C1SH240 (santalol). When boiled with alcoholic potash, these esters are hydrolysed (saponified) and yield the free alcohol and the potassium salt corresponding with the acid of the ester. Thus, the volatile oils containing esters have saponification numbers, which may be determined in a manner analogous to that used for fatty matters. 

Free Alcohols alone.—In this case the content in free alcohols (borneol, geraniol, terpineol, linalool, menthol, citronellol, santalol, thujyl alcohol) is determined by transforming the alcohols into the corresponding acetates by boiling with acetic anhydride and then determining the saponification number of the acetylated product acetyl saponification number). 

Fontes et al. (1998b) studied the enantioselectivity of cutinase and found that it was very selective toward one enantiomer with an enantiomeric excess of almost 100%. They found that the enantioselectivity was very sensitive to changes in water content. Bornscheuer et al. (1992) studied hydrolysis, esterification, and transesterification in carbon dioxide to try to find the best method for producing enantiomerically pure substances in carbon dioxide. They found that the thermodynamically favored hydrolysis led to higher enantiomeric excess with less enzyme in the shortest time. Michor et al. (1996b) also examined more than one system to determine a better route to product and found that while the transesterification of -menthol was fast and resulted in high enantiomeric excess, resolution of -citronellol was not feasible. The reaction rate for the reaction of -citronellol was 10-20 times of that of -menthol, but was not selective. 

BET surface area of the support, t- determined from XRD, J- selectivity to citronellol. 

The total alcohols are determined by acetylation in the usual manner, and the citronellol by formylation. The formylation process is carriedi out as follows —... 

The relative proportions of the two alcohols, geraniol and dtronellol, in oil of geranium oil is a matter of considerable interest, and the determination is frequently of importance. The only method available in practice for this purpose is the combination of the acetylation process, which gives the measure of the total alcohols and the formylation process, by which the geraniol is decomposed, and the citronellol estimated. 

This method has been referred to under Otto of Bose, but has been more critically studied by Simmons in reference to geranium oil. Simmons has shown that the determination of citronellol in the presence of geraniol by the formylation process is not strictly accurate, but tbe results are exceedingly useful for comparative purposes. 

To prove whether the results obtained represent the true citronellol-content Simmons determined the total alcohols by acetylation, and the citronellol by formylation of (1) pure geraniol, (2) pure citronellol, and (3) a mixture of (1) and (2) in equal proportions, with the following results —... 

It would appear fi om these results that the citronellol-content of the Asia Minor oil is undoubtedly the highest, whilst that of Algerian oil is the lowest. These observations are confirmed by the odour, indicating that the determination of citronellol-content is not only a useful factor, but closely follows the nose in judging the value of a particular oil. 

Melting and Solidifying-Points—Boiling-Point and Distillation— Determination of Esters—Determination of Alcohols— Tables for the Calculation of Esters and Alcohols—Separate DMermination of Citronellol in Presence of Gwaniol—Determination of Aldehydes and Ketones— Miscellaneous Processes—Determination of Phenols—Detection of Chlorine—Determination of Hydrocarbons—Detection of some Common Adulterants. 

A new method for determination of hydroxyl groups in primary alcohols and secondary alcohols, but not tertiary alcohols, has been described by Sully in which stearic anhydride is used instead of acetic anhydride. Among the compounds successfully assayed were citronellol, geraniol, benzyl alcohol, phenylethyl alcohol and menthol. The procedure has also been used for determining phenols including eugenol. 

Table 6.7 summarizes results obtained in four different reactor types at two different citronellol concentrations. Yields and ratios were determined by H NMR analysis with internal standard after treatment of the crude reaction mixture with NaBH4. Entry 7 represents results achieved in a scaled-up dualchannel reactor, which has a total volume of 285 pi. Hence, the reactor volume is increased by a factor of 7 compared to the dual-channel reactor applied for entries 1 and 4. 

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