Into an iron or copper reaction vessel having an efficient stirring device and furnished with a refluxing column and condenser, were charged 330 lb of high quality meta-cresol and 150 lb of glycerol, together with 25 lb of sodium acetate to serve as the catalyst in the reaction. The reaction mixture, of this composition, was then heated to 250°C. The water of the reaction distilled off during the heating as the ether formation proceeded, this removal of water from the reaction chamber being promoted by the presence of the excess of phenol, some of which also continued to distill over. Towards the end of the reaction, after about 12 hours, when about 60% of the glycerol had been converted, at which point the reaction slowed down and the distillate was mainly cresol, the batch was cooled and 50 gallons of water were added to it along with 150 lb of xylene. As the result of these additions and the cooling down of the material the batch stratified into an aqueous layer containing unreacted glycerol, polyglycerols and sodium acetate, and a nonaqueous layer containing the ethers that had been formed in the reaction, together with unreacted cresol which remained in the reaction chamber, dissolved in the xylene that had been added to the batch. The aqueous layer was then separated and the water content removed therefrom by evaporation to a degree suitable for the recovery of the glycerol and sodium acetate contents of the layer, for their reuse in the process in a succeeding batch therein. The separated nonaqueous layer containing the ethers was distilled to recover the xylene and cresol contents respectively as the early fractions of the layer thus subjected to distillation. The cresol thus recovered, together with the cresol recovered from the distillate obtained during the heating of the reaction mixture, was returned to the process for reuse in a succeeding batch. Redistillation of the ether mixture recovered is usually necessary and desirable, particularly from the point of view of removing last traces of cresol therefrom. The yield of mixed ethers in this example was about 200 lb, in the relative proportions stated of about 70 parts of monoether to 30 of diether.
World Health Organization (WHO)
Mephenesin, a centrally acting muscle relaxant and sedative, was
introduced in 1948 and its use has subsequently been associated with some of the
undesirable features of barbiturate use. It is of limited efficacy since it is shortacting
and does not relieve the spasticity associated with chronic neurological
disorders. It has therefore been largely superseded by benzodiazepines but it
remains available in some countries.
