Sodium Methylate and Its Uses SODIUM
METHYLATE, now
available in
commercial quantities, is a versatile reagent for organic syntheses. Formerly it was prepared in solution as needed in the laboratory, and its early commercial ap plications used the same procedure. But the solvent-free powder offers such ad vantages that it is now taking its right ful place among the reagents used in the fields of pharmaceuticals, dyes, perfumes, and organic intermediates. It may be em ployed either to supply the user's entire requirement of the reagent or to build up the concentration of the dilute solution prepared in the user's plant. Although very common in the research laboratory (11), the use of the alcoholates in industry has until recently been limited by the fact that they have not been avail able commercially. The preparation of the alcoholate by the user himself is repre sented by the simple reaction:
tions of the alcoholates which have been indicated by laboratory research. Among the special uses that have in creased the demand for sodium methylate is the manufacture of sulfadiazine, which requires a sodium methylate of relatively low alcohol and sodium hydroxide con tent. Manufacture of Dry Sodium Methylate
The process used for the manufacture of sodium methylate is analogous to that (the Castner electrolytic process) which Mathieson has used for many years in producing caustic soda and chlorine. In the operation of the Castner mercury cell, a solution of sodium chloride is electrolyzed, the chlorine being discharged at the graphite anode and the sodium being deposited at a mercury cathode where it forms sodium amalgam. The violent reaction of sodium with water to form hydrogen gas and sodium hydroxide solution does not occur with the brine, owing to the high overvoltage of hydrogen on the sodium amalgam sur face. The amalgam is transferred either to another compartment of the cell or to a separate piece of equipment in which the sodium is caused t o react with water in electrical contact with a conductor of electricity having α low overvoltage of hydrogen. The hydrogen forms at this electrode and the sodium remains in the solution as sodium hydroxide. Modifications and improvements in this basic process have been made over a
G . D.
Byrlcit and E. C. Soule
Research Department The Mathieson
Alicaii Works (Inc.)
Niagara Falls, Ν . Ύ.
period of years by Mathieson chemists and engineers, the most recent by Gardi ner, Richardson, and Taylor (16, 27, SO). In practice, however, the procedure is These improvements are concerned with not quite so simple. Sodium is a reactive methods of purifj'-ing and handling brine, metal to be used only with suitable pre cell construction, particularly as applied cautions, and in inexperienced hands is a to stationary cells, and increasing the dangerous reagent. The product of the capacity of amalgam discharge equipment. reaction is usually a dilute solution of the In manufacturing sodium methylate, alcoholate in alcohol and the large excess the amalgam is formed in the same way as of alcohol is frequently a disadvantage. in caustic soda manufacture. However, Traces of moisture, easily taken up by the instead of reacting with water, the amal solution from the atmosphere, cause gam is made to react with methanol. hydrolysis to sodium hydroxide, adversely Gaseous hydrogen is formed in this reac affecting subsequent yields. For these tion and the sodium remains behind as reasons, industry has only recently begun sodium methylate dissolved in methanol. to recognize the many potential applica Th« reaction may be accomplished by means of graphite in contact with both the amalgam and methanol, a tower being particularly advantageous for this pur pose (80). The tower is packed with 3>*y éocUutft éHeiUêflaie UG4 lece+ttùf, ù&e+t fptade cantt+i&uUcUléf CMACÙI- 0.375-inch pieces of graphite. Amalgam aJUe cuu£ i4 GJsiecuLéf i*t 444e 44* loAae vaUitne, fUitUcdtlasUtf. frvi tlte flows in near the top, countercurrent to 4ftaM44l)ac4*44*je. ojj txàicU** fJt&uHGceuticaL·. ût li a tuJtite pauujLe*r methanol introduced at the bottom, and the reaction forms hydrogen, depleted r-uttaitU+Uf G 4ft44u*M444ft &{f 95°J0 o£ éocLiutfi tHetlufloute, 4*ato
