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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. The proton NMR spectrum of cyclohexane is a singlet at room temperature, with no separation into separate signals for axial and equatorial hydrogens.
Substituents on a cyclohexane ring prefer to reside in the equatorial position to the axial. The difference in Gibbs free energy (ΔG) between the higher energy conformation (axial substitution) and the lower energy conformation (equatorial substitution) is the A-value for that particular substituent.
Chemical structure of cyclohexane, with indication of axial (red) and equatorial (blue) bonds by colors. Date: 30 July 2006: Source: Selfmade with ChemDraw. Author: Calvero. Permission (Reusing this file) PD. Other versions: Image:Cyclohexane structure.png.
English: Cyclohexane chair flip (ring inversion) reaction. Structures of the significant conformations (A, B, C & D) of the reaction are shown & plotted against their ...
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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. Source for the conformation names & claim of lowest/highest energy:
In cyclohexane the ring strain and eclipsing interactions are negligible because the puckering of the ring allows ideal tetrahedral bond angles to be achieved. In the most stable chair form of cyclohexane, axial hydrogens on adjacent carbon atoms are pointed in opposite directions, virtually eliminating eclipsing strain.
Cyclohexane is a prototype for low-energy degenerate ring flipping. Two 1 H NMR signals should be observed in principle, corresponding to axial and equatorial protons. However, due to the cyclohexane chair flip, only one signal is seen for a solution of cyclohexane at room temperature, as the axial and equatorial proton rapidly interconvert ...