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Synthesis method and process of D,L- pantothenolide

    One, isobutyl aldehyde, glyoxylic acid method
    When glyoxylic acid and isobutylaldehyde are combined in aqueous solution of NaOH with hydroxylaldehyde condensation reaction; After the reaction, heating up, and then adding glyoxylic acid (or formaldehyde) and sodium hydroxide for several hours of disproportionation reaction after a period of reaction; After the reaction of the reaction liquid after decompression steam out the appropriate amount of water, the remaining reaction liquid with organic solvent extraction of 2, 4-dihydroxy-3, 3-dimethylbutyrate sodium; According to the acidity and alkalinity of the reaction solution, the ph value of concentrated hydrochloric acid was adjusted to 2-3, and the neutralization reaction was carried out by heating reflux. Then steam away the water to concentrate and filter out the crystallized nacl; After the organic solvent in the mother liquor was removed by evaporation, crude d, L – pantothenolide was obtained. The equation is as follows:

    (1) hydroxylaldehyde condensation reaction
    (2) Disproportionation reaction
    (3) esterification reaction

    The disadvantages of this method are: 1) the use of expensive glyoxylic acid as raw material and high consumption; 2) It consumes a large amount of alkali and acid and produces a large amount of salt by side, which makes wastewater treatment costly and difficult; 3) It is necessary to add organic solvent extraction, which is cumbersome and costly.

    Two, isobutyral, hydroxyl acetonitrile method
    Isobutyl aldehyde and hydroxy acetonitrile solution to add reaction, the reaction in the presence of alkaline catalyst is needed to go smoothly, heating temperature and heat preservation hours make the reaction completely, the reaction mixture into inorganic acid hydrolysis, excessive acid with alkali neutralization processing, remove excess moisture evaporation, concentration to filter to remove after salt crystals, D, L – pantothenolactone was obtained by organic solvent extraction and rectification. The equation is as follows:

    The disadvantages of this method are as follows: 1) Hydroxy acetonitrile is easy to decompose and polymerize under alkaline conditions, resulting in high consumption, dark reaction liquid and difficult wastewater treatment; 2) It is necessary to add organic solvent extraction, which is cumbersome and costly.

    Three, isobutyl aldehyde, formaldehyde, hydrocyanic acid method
    Formaldehyde and isobutyl aldehyde under the effect of alkaline catalysts for aldol condensation reaction, condensation join hydrocyanic acid, after the completion of cyanide under the process temperature alcoholize reaction, reaction after joining sulfuric acid or hydrochloric acid reflux hydrolysis, after hydrolysis neutralization and evaporation to remove excess water, filtered to remove after enrichment to the salt crystals, D, L-pantothenolide was obtained by extraction and rectification with organic solvent (ethyl acetate). The equation is as follows:

    The disadvantages of this method are as follows: 1) Hydroxy tevaleral is poor in water solubility, leading to the cyanidation reaction must be carried out in a large amount of water at a higher temperature, resulting in a large amount of waste water and high energy consumption for evaporation; 2) The product uses a large amount of ethyl acetate extraction (5 tons/ton), which has high recovery energy consumption and high solubility of ethyl acetate in water (8.3g/100g water), resulting in large solvent loss and difficult wastewater treatment, which is not conducive to environmental protection.

    Therefore, it is of great significance to develop a green, easy to operate and low-cost synthesis method of D, L-pantothenolide for green industrial production of calcium d-pantothenate.

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