What distinguishes List 1 chemicals from other chemicals?

List 1 chemicals are distinguished by being specifically designated by the Drug Enforcement Administration (DEA) for legitimate uses, which is why the correct answer focuses on this aspect. These chemicals are often precursors or essential components used in the synthesis of controlled substances and are regulated because they have a high potential for abuse. Understanding that they have legitimate applications in medical and research contexts is crucial, as this regulation is designed to prevent their diversion for illicit uses while still recognizing their value in lawful settings.

In contrast, the other choices suggest limitations that do not accurately reflect the nature of List 1 chemicals. While they may not be used exclusively for recreational purposes, claiming that they are only for medical research fails to account for their broader legitimate applications. Meanwhile, stating that they have no legal applications overlooks the regulatory framework which allows for their controlled use. These distinctions are essential in comprehending the regulatory landscape surrounding chemicals with potential abuse, which is the central focus of understanding List 1 chemicals.