The stereochemistry of α − D − idopyranose with respect to equatorial and axial chair conformations is to be explained. Concept introduction: 舧 Chair conformations: It is the most stable conformation, which accurately shows the spatial arrangement of atoms. 舧 Equatorial bonds are parallel to the average plane of the ring, whereas axial bonds are perpendicular to the average plane of the ring. 舧 The conformation having bonds at the equatorial positions are more stable than those with bonds at the axial position. 舧 On flipping the cyclohexane ring, axial bonds become equatorial bonds and equatorial bonds becomes axial bond. 舧 Bulkier group acquires equatorial positions to form stable conformer due to steric factors. 舧 The most stable configuration of aldopyranoses is when the − CH 2 OH group exists in equatorial conformation. 舧 Stereochemistry: The equatorial orientation refers to the spatial arrangement of − CH 2 OH group at C-2 in the same plane, and the axial orientation refers to the spatial arrangement of − CH 2 OH group at C-2 along the axis. 舧 The stability of the atom can be estimated at the values of the anomeric effect of the O:OH bonds. 舧 The anomeric effect is lowest for sugars with equatorial orientation, which results in lower energetic state, and consequently this type of orientation confers higher stability. 舧 The anomeric effect is highest for sugars with axial orientation, which results in higher energetic state, and consequently this type of orientation confers lower stability.

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Chapter 22, Problem 30P

Interpretation Introduction

Interpretation:

The stereochemistry of α−D−idopyranose with respect to equatorial and axial chair conformations is to be explained.

Concept introduction:

舧 Chair conformations: It is the most stable conformation, which accurately shows the spatial arrangement of atoms.

舧 Equatorial bonds are parallel to the average plane of the ring, whereas axial bonds are perpendicular to the average plane of the ring.

舧 The conformation having bonds at the equatorial positions are more stable than those with bonds at the axial position.

舧 On flipping the cyclohexane ring, axial bonds become equatorial bonds and equatorial bonds becomes axial bond.

舧 Bulkier group acquires equatorial positions to form stable conformer due to steric factors.

舧 The most stable configuration of aldopyranoses is when the −CH2OH group exists in equatorial conformation.

舧 Stereochemistry: The equatorial orientation refers to the spatial arrangement of −CH2OH group at C-2 in the same plane, and the axial orientation refers to the spatial arrangement of −CH2OH group at C-2 along the axis.

舧 The stability of the atom can be estimated at the values of the anomeric effect of the O:OH bonds.

舧 The anomeric effect is lowest for sugars with equatorial orientation, which results in lower energetic state, and consequently this type of orientation confers higher stability.

舧 The anomeric effect is highest for sugars with axial orientation, which results in higher energetic state, and consequently this type of orientation confers lower stability.

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