PROCESS FOR PREPARING 1,2,3,4-TETRAHYDRO-2-METHYL-1,4- DIOXONAPHTHALENE-2-SULFOACID SODIUM SALT (VICASOL) Russian patent published in 1999 - IPC

FIELD: chemical industry. SUBSTANCE: process for preparing 1,2,3,4-tetrahydro-2-methyl-1,4-dioxonaphalene- 2-sulfoacid sodium salt (vicasol) comprises reacting 2- methyl-1,4-napthoquinone (menadione) with sodium bisulfite (NaHSO₃) aqueous solution. Reaction is carried out in two-phase system consisting of aqueous phase and incombustible organic solvent. Aqueous phase is essentially sodium bisulfite solution having concentration from 4 to 6.5 mole/l, and organic phase is menadione solution. Reaction is carried out at temperature of not higher than 40 C. These conditions simplify and make cheaper technology of regeneration of organic solvents and also method of purification and recovery of vicasol. The resulting product comprises 0.5-2 wt % Na₂S₂O₅ which stabilizes vicasol and maintains its proper storage and light resistance. EFFECT: more efficient preparation process. 5 cl