C5H11

C5H11 is the molecular formula associated with several five-carbon alkyl groups derived from pentane by loss of one hydrogen. As a general notation, C5H11- denotes an alkyl substituent that can attach to a larger molecule, rather than a standalone neutral compound. The saturated hydrocarbon with five carbons is pentane (C5H12); removing one hydrogen yields a radical or substituent of formula C5H11.

There are multiple structural isomers that correspond to C5H11-, reflecting different attachment points and branching on the pentane skeleton. Common examples include n-pentyl (pentan-1-yl), where attachment occurs at the terminal carbon; pentan-2-yl (sec-pentyl), with attachment at the second carbon; 3-methylbutan-1-yl (isopentyl), a branched primary substituent; and 2,2-dimethylpropyl (neopentyl), a highly branched primary substituent involving a neopentyl arrangement. These examples illustrate that C5H11- can refer to several distinct alkyl groups that share the same formula but differ in structure.

Molar mass of the C5H11 moiety is about 71.1 g/mol. In chemical contexts, C5H11 groups are encountered when building esters, ethers, halides, and other alkylated products. The physical and chemical properties of C5H11-containing compounds depend on the specific isomer and how the group is attached to the rest of the molecule.

See also: pentane, alkyl group, isopentyl, neopentyl.