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Axial – along the center of a round body, or the axis of rotation of a body Radial – along a direction pointing along a radius from the center of an object, or perpendicular to a curved path. Circumferential (or azimuthal ) – following around a curve or circumference of an object.
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 ...
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.
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. [23]
At the end of the process, all axial positions have become equatorial and vice versa. The overall barrier of 10.8 kcal/mol corresponds to a rate constant of about 10 5 s –1 at room temperature. Note that the twist-boat ( D 2 ) conformer and the half-chair ( C 2 ) transition state are in chiral point groups and are therefore chiral molecules.
Model of the equatorial coordinate system. Declination (vertical arcs, degrees) and hour angle (horizontal arcs, hours) is shown. For hour angle, right ascension (horizontal arcs, degrees) can be used as an alternative. The equatorial coordinate system is a celestial coordinate system widely used to specify the positions of celestial objects.
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 ...
The angle between the Earth's equatorial plane and the ecliptic, ε, is called the obliquity of the ecliptic and ε ≈ 23.4°. An equinox occurs when the earth is at a position in its orbit such that a vector from the earth toward the sun points to where the ecliptic intersects the celestial equator.