Monochlorinated

Part of speech: adjective

Definitions

1. Containing exactly one chlorine atom that has replaced a hydrogen atom in a chemical compound
2. Describing a molecule in which a single chlorine atom has been introduced in place of one hydrogen
3. Chemically modified so that just one chlorine atom is bonded to a compound in place of hydrogen

Etymology: Monochlorinated is built from "mono-", from Greek "monos" meaning "single" or "alone," attached to "chlorinated," the past participle of "chlorinate." Chemists use the form to describe a compound or process in which exactly one chlorine atom has been introduced into a molecule, so the prefix does the counting while the rest of the word names the operation. The root "chlor-" comes from Greek "chlōros," meaning "pale green" or "greenish-yellow," a nod to the colour of chlorine gas. Chemists later attached "-ate" and "-ed" to build the verb "chlorinate," meaning to treat or combine a substance with chlorine. Because chlorine is a reactive gas, the word's core idea is simply adding chlorine to something, and "monochlorinated" narrows that to a single substitution. Chemists use the word mainly in organic chemistry, where a hydrogen atom on a carbon-based molecule is swapped for a chlorine atom, and the number of such swaps distinguishes related products such as monochlorinated, dichlorinated and trichlorinated versions of the same parent compound.