immediate precursor
(23) The term “immediate precursor” means a substance— (A) which the Attorney General has found to be and by regulation designated as being the principal compound used, or produced primarily for use, in the manufacture of a controlled substance; (B) which is an immediate chemical intermediary used or likely to be used in the manufacture of such controlled substance; and (C) the control of which is necessary to prevent, curtail, or limit the manufacture of such controlled substance.