One method for making NaCN is the reaction of 2K4FeCN6 + 7H2SO4 = 12HCN + 2FeSO4 +2KHSO4 +K2SO4. The HCN is distilled into 50% NaOH...after awhile the solution turns dark brown and you can smell ammonia.The reaction is likely 8NaCN +3H2CO3(from water and CO2)=2NH3 + 6NaOCN + Na2CO3 + 2C What can be done to reverse this reaction?Is there any way to get rid of the dark brown color? The Merck Index says water solutions of NaCN rapidly decompose...if that is true then how are any SN2 reactions done with NaCN in water--ethanol solution?The internet has next to nothing on this problem.
Solution: NaCN is a strong nucleophile. I think that in order for sodium cyanide not to decompose, it is necessary to add DMSO, ie, to react in the presence of the presence of a solvent DMSO. DMSO, a very aggressive solvent, will block the reactions that occur in the environment.