Intermediate Topic 755 of 1102 Organic Chemistry
Conformations
Different spatial arrangements arising from rotation about single bonds.
In-depth explanation of Conformations
Conformations are different spatial arrangements of a molecule that arise from rotation about single bonds, without breaking any bonds. At room temperature these arrangements interconvert very rapidly, so they are not separate compounds that can be isolated. Their energies differ because of torsional strain from eclipsed bonds and steric repulsion between bulky groups, so one conformer usually dominates. Understanding conformations is essential for explaining reaction rates and product stereochemistry.
Going deeper: Conformations
Key ideas: Conformers are rotamers produced by rotation about single bonds. Ethane has a torsional barrier of about 12 kJ/mol (staggered more stable than eclipsed). Butane has anti (most stable), gauche (about 3.8 kJ/mol higher) and eclipsed forms, the fully eclipsed one (methyls together) being about 19 kJ/mol above anti. Conformers interconvert rapidly at room temperature and cannot be isolated.
Common mistakes and connections: Students treat conformers as different compounds or isomers worth naming. Another mistake is attributing the ethane barrier mostly to steric repulsion; hyperconjugation in the staggered form is a major factor. Links to Newman projections, ring strain and the chair form of cyclohexane.
Visualization of Conformations
Rotating ethane about its C-C bond passes through staggered minima and eclipsed maxima 12 kJ/mol higher. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Butane has an anti conformation, in which the two methyl groups are opposite each other, and gauche conformations, in which they are closer together.
Frequently asked questions about Conformations
What is Conformations?
Different spatial arrangements arising from rotation about single bonds.
Is Conformations a beginner, intermediate or advanced topic?
Conformations is a intermediate topic in Organic Chemistry. It builds on the vocabulary of beginner topics in this area.
What should I learn before Conformations?
Study these earlier topics in Organic Chemistry first: Optical Activity, CIP Priority Rules, Fischer Projections.
What comes after Conformations?
The next topics in Organic Chemistry are Newman Projections and Cyclohexane Chair Conformation.
Can I practise Conformations with quizzes?
Yes. The interactive lesson includes a self-check question on Conformations, and the Organic Chemistry quiz draws on every topic in this area.
Where Conformations fits in Organic Chemistry
Conformations is topic 27 of 148 in Organic Chemistry.