C18H37

C18H37 is a chemical formula representing a hydrocarbon composed of 18 carbon atoms and 37 hydrogen atoms. In practice, this formula most often denotes an octadecyl group (the octadecyl substituent) rather than a standalone stable molecule. The saturated hydrocarbon with 18 carbons is octadecane, which has the formula C18H38; therefore C18H37 typically indicates a reactive site on a larger molecule rather than an isolated compound.

As a long-chain alkyl group, C18H37 is nonpolar and highly hydrophobic. It is commonly encountered as a substituent in a variety of chemical derivatives, including esters, amides, ethers, and surfactants. In these contexts, the octadecyl group contributes to lipophilicity and increases the hydrophobic character of the parent molecule, influencing properties such as solubility, melting behavior, and phase behavior in mixtures.

Isomerism and structure: While the formula C18H37 does not specify a particular arrangement, there are many possible isomers for an 18-carbon chain. A straight-chain form (n-octadecyl) and several branched forms can give the same empirical formula. When used as a substituent, the exact structure and attachment point affect the physical properties and reactivity of the resulting compound.

Applications and safety: Long-chain alkyl groups are widely used in cosmetics, coatings, and polymer chemistry, where they help modify texture, water resistance, and stability. Like other hydrocarbons, materials containing long alkyl chains are typically flammable and must be handled with standard laboratory or industrial safety practices.