formerly occas. -ule, a terminal element of chemical terms, ad. F. -yle (also -ule), f. Gr. ὔλη wood, matter, substance (see HYLE), used for ‘chemical principle, radical.’ It was introduced by Wöhler and Liebig (Ann. de Chimie, 1832, LI. 286), and first used by them in the term benzoyle; other early names were éthyle (éthule), élayle (Berzelius), dadyle, peucyle, citronyle, citryle (Blanchet and Sell). Some fifteen in anglicized form, including acetyl, amyl, cinnamyl, glyceryl, salicyl, appear in the Elements of Chemistry by T. Graham, 1842, who also invented the general term basyle for a body which unites with oxygen to form a base. Methyl is peculiar in being a back-formation from methylene.
-yl is used in forming the names of radicals compounded of two or three elements in various atomic proportions, which behave in combination like simple elements and are the constant bases of series of compounds (though they may not be themselves obtainable in a free state). Thus carbonyl CO, hydroxyl HO, sulphuryl SO2, are compounds of carbon, hydrogen, and sulphur, respectively. The greater number are compounds of carbon and hydrogen, either alone, as amyl, ethyl, deutyl, trityl, or with oxygen, as acetyl, lactyl.
