Rotamer

In <a href="/facts/Chemistry/SrNqkGVm">chemistry</a>, rotamers are chemical species that differ from one another primarily due to rotations about one or more <a href="/facts/Single_bond/8qz02fEl">single bonds</a>. Various arrangements of <a href="/facts/Atom/FoQ4kGN5">atoms</a> in a <a href="/facts/Molecule/N9ljSfFq">molecule</a> that differ by rotation about single bonds can also be referred to as different conformations. Conformers/rotamers differ little in their energies, so they are almost never separable in a practical sense. Rotations about single bonds are subject to small energy barriers. When the time scale for interconversion is long enough for isolation of individual rotamers (usually arbitrarily defined as a <a href="/facts/Half-life/kGVH8BAB">half-life</a> of interconversion of 1000 seconds or longer), the species are termed atropisomers (see: <a href="/facts/Atropisomer/IWGqaLsT">atropisomerism</a>). The <a href="/facts/Ring_flip/1G0rpzsx">ring-flip</a> of substituted <a href="/facts/Cyclohexane/FDAW5j8v">cyclohexanes</a> constitutes a common form of conformers.
The study of the energetics of bond rotation is referred to as conformational analysis. In some cases, conformational analysis can be used to predict and explain product selectivity, mechanisms, and rates of reactions. Conformational analysis also plays an important role in rational, structure-based <a href="/facts/Drug_design/XAU0Ke3d">drug design</a>.

Rotamer open-in-new

Rotamer