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According to the VSEPR theory of molecular geometry, an axial position is more crowded because an axial atom has three neighboring equatorial atoms (on the same central atom) at a 90° bond angle, whereas an equatorial atom has only two neighboring axial atoms at a 90° bond angle. For molecules with five identical ligands, the axial bond ...
This means it costs 1.74 kcal/mol (7.3 kJ/mol) of energy to have a methyl group in the axial position compared to the equatorial position. A-values are numerical values used in the determination of the most stable orientation of atoms in a molecule ( conformational analysis ), as well as a general representation of steric bulk .
An atom bonded to 5 other atoms (and no lone pairs) forms a trigonal bipyramid with two axial and three equatorial positions, but in the seesaw geometry one of the atoms is replaced by a lone pair of electrons, which is always in an equatorial position. This is true because the lone pair occupies more space near the central atom (A) than does a ...
Trigonal bipyramid molecules have both with axial and equatorial positions. If there are two types of substituents, the more electronegative substituent will prefer the axial position as there are smaller bond angles between axial and electronegative substituents than between two equatorial substituents.
The T-shaped geometry is related to the trigonal bipyramidal molecular geometry for AX 5 molecules with three equatorial and two axial ligands. In an AX 3 E 2 molecule, the two lone pairs occupy two equatorial positions, and the three ligand atoms occupy the two axial positions as well as one equatorial position. The three atoms bond at 90 ...
Trigonal bipyramidal molecular shape ax = axial ligands (on unique axis) eq = equatorial ligand (in plane perpendicular to unique axis). The Berry mechanism, or Berry pseudorotation mechanism, is a type of vibration causing molecules of certain geometries to isomerize by exchanging the two axial ligands (see the figure) for two of the equatorial ones.
Hydrogen atoms in axial positions are shown in red, while those in equatorial positions are in blue. Cyclohexane conformations are any of several three-dimensional shapes adopted by cyclohexane . Because many compounds feature structurally similar six-membered rings , the structure and dynamics of cyclohexane are important prototypes of a wide ...
As described by the VSEPR model, the five valence electron pairs on the central atom form a trigonal bipyramid in which the three lone pairs occupy the less crowded equatorial positions and the two bonded atoms occupy the two axial positions at the opposite ends of an axis, forming a linear molecule.