Laboratoire “Dauphin” published the artcileThe determination of citronellal, HPLC of Formula: 42822-86-6, the main research area is .
Cf. Holtappel, C. A. 22, 1214. The original Dauphin method is as follows: weigh 2 g. oil in a 100-cc. flask, add 20 cc. of 5% alc. NH2OH.HCl previously neutralized to helianthin, immediately titrate the liberated HCl with 0.2 N KOH in presence of helianthin. Holtappel’s modifications consist essentially in cooling the solution with ice, use of excess alkali with back titration after 15 min., and use of bromothymol blue instead of helianthin. Investigation of the effects of temperature showed negligible variations (maximum 0.5%) from 0° to 35°. Investigation of the causes of the irregularities in results obtained by Holtappel brought out the following facts: (1) citronellal is cyclicized by strong acids into isopulegol and its derivatives, there being formed chiefly hydroxy-3-ethoxy-8-p-menthane in alc. solution, while in hydro-alc. solution there is formed a mixture of this compound with 3,8-p-menthane diol; (2) neither of these compounds combines with NH2OH.HCl, and their formation leads to low results; (3) in strongly alc. solution these reactions are of secondary importance, there being formed citronellal ethylacetal, which protects the aliphatic mol. against cyclization; (4) contrary to generally accepted data, this reaction is almost instantaneous, even at -15°; (5) slight acidity catalyzes oximation before cyclization can take place to any appreciable extent. It is concluded that: (1) helianthin should be used as indicator, as the turning point of bromothymol blue is at such a low pH value of the solution that appreciable cyclization can occur, while a light red color with helianthin indicates optimum conditions for oximation and absence of cyclization; (2) the alc. KOH should be added sufficiently quickly to avoid production for any appreciable time of the distinct red characteristic of relatively high acidity, and sufficiently slowly to prevent high alkalinity which might slow the reaction and even prevent it from going to completion through formation of the fairly stable acetal. The fact that Holtappel obtained lower results by oximation in alk. solution than by oximation at low temperature in acid solution is attributed to the fact that, because of the use of bromothymol blue instead of helianthin, the true effects of acidity could not be detected. The original Dauphin method is more simple and rapid than Holtappel’s modification and is as accurate as the latter. The method is being applied in the Dauphin Laboratories to the determination of ketones in all essential oils (the determination of citronellal being the most delicate); and where the speed of the reaction is relatively low, by plotting curves the presence of several ketones in the same oil can frequently be brought out very clearly. The method is particularly suitable for determination of menthone in oil of mint, instead of the usual method of reducing with Na, washing, acetylating and saponifying
Parfums de France published new progress about Oils. 42822-86-6 belongs to class alcohols-buliding-blocks, name is 2-(2-Hydroxypropan-2-yl)-5-methylcyclohexanol, and the molecular formula is C10H20O2, HPLC of Formula: 42822-86-6.
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