CS224916B1 - The determination of the substances during the selective hydrogenation 3,7-dimethyl-9-/2,6,6-trimethyl-1-cyclohexene-1-y 1/-2,7-nonadiene-4-in -1,6-diol - Google Patents

Description

The invention relates to the qualitative and quantitative determination of solders in the reaction mixture by selective hydrogenation of 3,7-dimethyl / 2,6,6-trimethyl-1-cyclohexen-1-yl) -2,7-nonadien-4-yn-1,6 The diol of formula (I) is a reaction mixture formed in addition to the desired 3,7-dimethyl-9- (2,6,6-trimethyl-1-cyclohexen-1-yl) -2,4,7-nonatriene. of a 1,6-diol of formula II with an unreacted substrate of formula I with a prehydrogenation product.

The selective hydrogenation of the triple bond in the compound of formula I to the double bond in the compound of formula II is strongly dependent on optimal adherence to the reaction parameters such as catalyst quality, reaction temperature, stirring and especially reaction time. Η ,, Helv.Chim.Acta.35,446,1952 /. From the experience of using this catalyst, it is known that the desired 100% conversion of the compound of formula I is achieved at a higher hydrogen consumption than the theoretical consumption. With the consumption of hydrogen corresponding theoretically to 100% conversion of the compound of formula I, the reaction mixture is formed, in addition to the compounds of formulas I and II, by the product of prehydrogenation. Such a mixture cannot be processed to vitamin A of the desired quality mainly due to the presence of the compound of formula I. It is therefore necessary in each experiment or batch to find the optimum hydrogen consumption so that the hydrogenation reaction contains at least was not significantly reduced due to pre-hydrogenation. For this, an analytical method is required, which allows the determination of the compounds of formulas 1 and 11 as well as the product of the prehydrogenation, both operatively and simultaneously.

Gas chromatography is an austerely accurate, operative yet commercially available analytical method, but is not suitable for direct monitoring of selective hyarogenation of a compound of formula 1, due to the thermal lability of all test substances under the conditions necessary for their determination, qualitatively and quantitatively. It is not possible to analyze by gas chromatography on gas, but after previous conversion of the hydrogenation mixture by treatment of hexamethyldisilazane and trimethylsilyl chloride in pyridine in ratios of 1: 1: 1 to 10: 1: 10 to the corresponding O- trimethylsilyl ethers and these are separated chromatographically on columns with suitable packings, preferably 1 to 10% dimethylpolysiloxane and 5 to 10% methylphenyl- (dimethyl) -siloxane on calcined acid-washed silica and silanized with dimethylchlorosilane. Optimum separation of the assayed substances was achieved using a 10% dimethylpolysiloxane cartridge on acid-washed calcined silica and silanized with dimethylchlorosilane in a 1 m glass column, at a column temperature of 5 ° K, with a retention time of 7.5 minutes, Formula II 8 , 8 minutes and the prehydrogenation product 6.7 minutes.

quantitative determination was done by the internal standard method. Eicosan was preferably used as internal standard. Statistics ** 2 **

224 916, while processing the results of the analyzes revealed that the analysis was free from systematic measurement errors. The positive standard for the compound of formula (i) is 1.82% and for the compound of formula (II) is

Hereinafter, the method of analysis is illustrated by the example without being limited to this.

Example analysis:

Using eicosane as the internal standard, and the model sample of compounds of formula 1, and if we zostrojiii function ^P I ^{/ P} ST ^{xf of Z and P} II ^{/ Pst = f ZM} I ^{/ F} st ^{/ »where} P - the area of I, II, or an internal standard,

M - linked mass of substance I, II or internal standard. A sample of the reaction mixture was filtered off the catalyst and the solvent was evaporated. Approximately 5 mg of the sample and 1 to 3 mg of eicosan were accurately weighed from the residue into a 5 ml vial. Add 1 ml of a solution consisting of hexamethyldisilazane and trimethylchlorosilane and dry pyridine in a 2: 1: 10 by volume ratio and quickly close the vial with a silicone rubber stopper. After shaking vigorously and standing for 5 minutes at room temperature, the sample is sampled through a septum for analysis and injected directly onto a chromatographic column. Chromatographic separation is performed on a 1 m long glass column packed with 10% dimethylpolysiloxane on a quenched acid-washed silica and silanized with dimethylchlorosilane (0.16-0.20 mm grain), at a working temperature of 508 K, a feed temperature of 523 K, and a carrier gas flow rate of 20 ml / min. Then, the compound of formula I has a retention time of 7.5 minutes, the compound of formula ΪΙ has a retention time of 8.8 minutes, and the prehydrogenation product of 6.7 minutes. The amounts of the compounds of formula I and II in the sample to be analyzed are calculated using the elution wave plots of the individual substances and the above-mentioned dependencies.

Claims (2)

Object of the invention 224 916 Method for determining substances in selective hydrogenation of 3,7-dimethyl-9- (2,6,6-trimethyl-1-yl) -2,7-nor) _{ADIENNE-4-yn-l>} 6-diol of the formula I to 3,7-dimethyl-9 / 2,6,6-trimethyl-l-cyclohexen-l-yl / _-2> 4 , 7-nonatrien _l-d 6 diol of formula II to mark tory in that the analyzed sample of the reaction mixture, by treatment with trimethylsilyl chloride and hoxametyldisilazánu in pyridine in a ratio of 1: 1: 1 and 10: 1: 10 was quantitatively converted into the corresponding O trimethylsilyl ethers, which is directly analyzed by gas chromatography on 1 to 10% dimethylsiloxane columns on acid-washed calcined silica and silanized with dimethylchlorosilane and quantitated by an internal standard method. Price: 2,40 Kčs Printed by Moravian Printing Works, plant 12, Leninova 21, Olomouc