C12H25

C12H25 is a chemical formula representing a hydrocarbon fragment containing twelve carbon atoms and twenty-five hydrogen atoms. As written, it does not describe a neutral, closed-shell alkane, since the corresponding saturated alkane with twelve carbons is C12H26 (dodecane). The composition C12H25 more commonly denotes a hydrogen-deficient fragment, typically a radical such as the dodecyl radical, C12H25•, or another charged or unsaturated species.

In practical use, C12H25 appears as a substituent or fragment within larger organic molecules or as a transient species in chemical processes. Dodecyl radicals are encountered in radical reactions, including initiation steps in polymerization and various chain-transfer or scavenging processes. The formula is also used in mass spectrometry and related analyses to represent a hydrocarbon fragment that can arise from cleavage of longer alkyl chains.

Because C12H25 represents a radical or fragment rather than a stable neutral molecule, it lacks fixed physical properties like a single boiling point or melting point. Its exact structure can vary, with many possible isomers differing in how the 12 carbon atoms are arranged and where the radical site is located. In practice, the term is often used descriptively to indicate a dodecyl-type fragment rather than to name a specific, isolable compound.

See also: dodecyl group; alkyl radical; dodecane.