(1) The optical isomer, except as used in § 1308.11(d) and § 1308.12(b)(4) of this chapter. As used in § 1308.11(d) of this chapter, the term “isomer” means any optical, positional, or geometric isomer. As used in § 1308.12(b)(4) of this chapter, the term “isomer” means any optical or geometric isomer;
(2) As used in § 1308.11(d) of this chapter, the term “positional isomer” means any substance possessing the same molecular formula and core structure and having the same functional group(s) and/or substituent(s) as those found in the respective Schedule I hallucinogen, attached at any position(s) on the core structure, but in such manner that no new chemical functionalities are created and no existing chemical functionalities are destroyed relative to the respective Schedule I hallucinogen. Rearrangements of alkyl moieties within or between functional group(s) or substituent(s), or divisions or combinations of alkyl moieties, that do not create new chemical functionalities or destroy existing chemical functionalities, are allowed i.e., result in compounds which are positional isomers. For purposes of this definition, the “core structure” is the parent molecule that is the common basis for the class; for example, tryptamine, phenethylamine, or ergoline. Examples of rearrangements resulting in creation and/or destruction of chemical functionalities (and therefore resulting in compounds which are not positional isomers) include, but are not limited to: Ethoxy to alpha-hydroxyethyl, hydroxy and methyl to methoxy, or the repositioning of a phenolic or alcoholic hydroxy group to create a hydroxyamine. Examples of rearrangements resulting in compounds which would be positional isomers include: Tert-butyl to sec-butyl, methoxy and ethyl to isopropoxy, N,N-diethyl to N-methyl-N-propyl, or alpha-methylamino to N-methylamino.
21 CFR § 1300.01
Any term not defined in this part shall have the definition set forth in section 102 of the Act (21 U.S.C. 802), except that certain terms used in part 1316 of this chapter are defined at the beginning of each subpart of that part.