### Question
What is the definition of positional isomer?


### Answer
The definition of **positional isomer** is as follows in *21 CFR § 1300.01*:

> 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

#### Citation:
  - *21 CFR § 1300.01*
  - Heading: **Title 21-Food and Drugs > PART 1300—DEFINITIONS**

