Open-chain compound

 ( Molecular Geometry ) 

In chemistry, an open-chain compound (or open chain compound) or acyclic compound (Greek prefix α 'without' and κύκλος 'cycle') is a compound with a linear structure, rather than a Cyclic compound one. An open-chain compound having no is called a straight-chain compound (also spelled as straight chain compound). Many of the simple molecules of organic chemistry, such as the and , have both linear and ring , that is, both acyclic and cyclic compound. For those with 4 or more carbons, the linear forms can have straight-chain or branched-chain isomers. The lowercase prefix n- denotes the straight-chain isomer; for example, n-butane is straight-chain butane, whereas i-butane is isobutane. are isomers of alkenes, not of alkanes, because the ring's closure involves a C-C bond. Having no rings (aromatic or otherwise), all open-chain compounds are aliphatic.

Typically in biochemistry, some isomers are more prevalent than others. For example, in living organisms, the open-chain isomer of glucose usually exists only transiently, in small amounts; glucose is the usual isomer; and L-Glucose is rare.

Straight-chain molecules are often not literally straight, in the sense that their are often not 180°, but the name reflects that they are straight. For example, the straight-chain alkanes are wavy or "puckered", as the models below show.