Definition of thionyl in US English:



  • as modifier Of or denoting the divalent radical SO.

    ‘thionyl chloride’
    • ‘The methyl halide can be produced by reacting methanol with phosphorous halides, hydrogen halides, or, in the case of methyl chloride, thionyl chloride.’
    • ‘One milliliter of dry methanol was chilled on dry ice and 0.25 mL thionyl chloride added slowly.’
    • ‘Schedule 3 comprises a number of toxic or precursor chemicals with widespread industrial uses, such as phosgene, hydrogen cyanide, phosphorus trichloride and thionyl chloride.’
    • ‘The resulting ester was saponified under basic conditions to the free acid, converted to the acyl chloride with thionyl chloride, and then to the amide with anhydrous ammonia gas.’
    • ‘An excess of the dry commercially available alcohol was cooled to 0°C, and freshly distilled thionyl chloride was added.’


1857: so named by H. Schiff (see Schiff base).