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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 symmetry group is D 3d. All carbon centers are equivalent.
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.
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
2: half-chair (highest in energy) 3: twist-boat 4: boat 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.
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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.
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A is thus the most stable conformation &, of all the other conformations, occurs most often in room temperature. Valleys A & B are local energy minima & A is global minima. A & B can thus be classified as conformers.