Conformational isomerism is the phenomenon of molecules with the same structural formula but different conformations (conformers) of atoms about a rotating bond. Steric repulsion will make some conformers more favourable than others - i.e. they will have a lower energy level. A simplified example is that of a butane molecule viewed in the Newman Projection shown - i.e. as if viewed down the central C-C bond with relative rotations of C² and C³ illustrated. In chemistry, isomers are molecules with the same chemical formula and often with the same kinds of bonds between atoms, but in which the atoms are arranged differently. ... In science, a molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. ... Many chemical compounds, especially hydrocarbons, can exist in different geometric configurations. ... In chemistry, the conformation of a molecule is its spatial configuration. ... Properties For alternative meanings see atom (disambiguation). ... In chemistry, a chemical bond is the force which holds together atoms in molecules or crystals. ... Steric effects are the interaction of molecules dictated by their shape and/or spatial relationships. ... Butane is an alkane hydrocarbon with the molecular formula C4H10. ...

Potential energies

A measure of potential energy is stored in conformers with greater steric hindrance than the 'anti' conformer ground state. Potential energy (U, or Ep), a kind of scalar potential, is energy by virtue of matter being able to move to a lower-energy state, releasing energy in some form. ...

• Staggered a.k.a. gauche conformer - 16 kJ/mol
• Eclipsed H and CH₃ - 3.8 kJ/mol
• Eclipsed CH₃ and CH₃ - 19 kJ/mol

The eclipsed methyl groups exert a greater steric strain because of their greater electron density compared to lone hydrogen atoms. In chemistry a methyl-group is a hydrophobic Alkyl functional group which is derived from methane (CH4). ... Electron density is the measure of the probability of an electron being present at a specific location. ... General Name, Symbol, Number Hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1 (IA), 1 , s Density, Hardness 0. ...

Consequences

If the eclipsed conformations of an isomer have high enough potentials, they may prevent rotation of substituents to different staggered conformations at sufficiently low energy levels. This will result in a racemic mixture of conformations that may or may not have different reactivities in situations such as enzymatic reactions in which molecular shape is usually a key factor of operation. In chemistry, isomers are molecules with the same chemical formula and often with the same kinds of bonds between atoms, but in which the atoms are arranged differently. ... In organic chemistry, a substituent is an atom or group of atoms subsituted in place of a hydrogen atom on the parent chain of a hydrocarbon. ... In chemistry, a racemate is a mixture of equal amounts of left- and right-handed stereoisomers of a chiral molecules. ... Reactivity refers to the rate at which a chemical substance tends to undergo a chemical reaction in time. ... Neuraminidase ribbon diagram An enzyme (in Greek en = in and zyme = leaven) is a protein, or protein complex, that catalyzes a chemical reaction and also controls the 3D orientation of the catalyzed substrates. ...

Conditions

Conformational isomerism only occurs around single bonds as a result of the requirement of breaking one or more pi bonds to rotate substituents about a sigma bond axis in double and triple bonded atoms. Conformers sufficiently constrained to exhibit measurable isomerism are unique from various flavours of stereoisomers in the fact that changes in stereochemistry are independent from any mechanism and instead rely only on molecular energy. Geometry of the water molecule Molecules have fixed equilibrium geometries--bond lengths and angles--that are dictated by the laws of quantum mechanics. ... In organic chemistry, a substituent is an atom or group of atoms subsituted in place of a hydrogen atom on the parent chain of a hydrocarbon. ... Geometry of the water molecule Molecules have fixed equilibrium geometries--bond lengths and angles--that are dictated by the laws of quantum mechanics. ...

See also

• diastereomer
• enantiomer
• isomer
• chirality