CH2CH2CH2

CH2CH2CH2 is a chemical shorthand used to denote a structural fragment consisting of three linked methylene (CH2) units. In practice, it is not a standalone, isolable molecule but a motif found within larger organic compounds. As a fragment, it represents a three-carbon portion of a carbon chain.

When attached as a substituent in a larger molecule, the fragment commonly corresponds to the n-propyl group, written as -CH2-CH2-CH3. In this context the full substituent has the formula C3H7. If the fragment bridges two parts of a molecule (a propylidene-type linkage), the attachment pattern can yield a -CH2-CH2-CH2- segment with the formula C3H6, reflecting two bonds to substituents and a loss of terminal hydrogens.

Chemically, CH2 groups are aliphatic methylenes. Their presence influences properties such as hydrophobicity and flexibility in polymers and hydrocarbons. In spectroscopy, methylene hydrogens typically appear as aliphatic signals in 1H NMR around 0.9–1.5 ppm, and methylene carbons in 13C NMR around 20–40 ppm; infrared absorption for C–H stretches occurs near 2850–2960 cm−1.

Related topics include the broader concepts of alkyl groups, isomerism among C3H6 species (for example propene and cyclopropane), and the distinction between saturated alkane chains (such as propane, C3H8) and unsaturated or cyclic variants. CH2CH2CH2 serves as a useful shorthand in reaction schemes and polymer chemistry to indicate a three-carbon chain segment within a larger molecular framework.