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The chair conformation is the most stable conformer. At 298 K (25 °C), 99.99% of all molecules in a cyclohexane solution adopt this conformation.
The chair and twist-boat are energy minima and are therefore conformers, while the half-chair and the boat are transition states and represent energy maxima. The idea that the chair conformation is the most stable structure for cyclohexane was first proposed as early as 1890 by Hermann Sachse, but only gained widespread acceptance much later.
In addition, cyclohexane conformations can be used to indicate if the molecule has any 1,3 diaxial-interactions which are steric interactions between axial substituents on the 1,3, and 5 carbons. [7] Chair conformation of beta-D-Glucose The cyclohexane conformations in relation to the potential energy at each conformation
The chair conformation minimizes both angle strain and torsional strain by having all carbon-carbon bonds at 110.9° and all hydrogens staggered from one another. [2] The conformational changes that occur in a cyclohexane ring flip take place over several stages. Structure D (10.8 kcal/mol) is the highest energy transition state of the process.
Similarly, cis-1,2-dichlorocyclohexane consists of chair conformers that are nonidentical mirror images, but the two can interconvert via the cyclohexane chair flip (~10 kcal/mol barrier). As another example, amines with three distinct substituents (R 1 R 2 R 3 N:) are also regarded as achiral molecules because their enantiomeric pyramidal ...
Structure and properties Index of refraction, n D: 1.4262 at 20 °C Abbe number? Dielectric constant, ε r: 2.023 ε 0 at 20 °C Bond strength? Bond length [1] 230 pm H–C Bond angle: 109.5° H–C–H 109.5 °C–C–C 109.5° H–C–C: Magnetic susceptibility? Surface tension: 27 dyn/cm at 10 °C 25.3 dyn/cm at 20 °C 15.7 dyn/cm at 80 °C ...
When ring flip happens completely from chair-to-chair, hydrogens that were previously axial (blue H) turn equatorial & equatorial ones (red H) turn axial. Pink and orange arrows show how one can imagine how carbons are being "pushed" as one conformation turns into another.
The interconversion of equivalent chair conformers of cyclohexane (and many other cyclic compounds) is called ring flipping. Carbon–hydrogen bonds that are axial in one configuration become equatorial in the other, and vice versa. At room temperature the two chair conformations rapidly equilibrate.