Question

Observations. нь со скрипис 9. Build the cyclopentane ring and study the angle strain and torsional strain in the ring. Draw the structures to explain these factors. Cyclopentane actually assumes a slightly puckered "envelope" conformation that reduces the eclipsing and lowers the torsional strain. Convince yourself about this fact. Provide the relevant drawings. 10. Build the cyclohexane ring and study the angle strain and torsional strain. Build the chair and boat conformations and identify the axial and equatorial bonds. Also identify the "flagpole hydrogens" in the boat conformation. Also study the half-chair and twist-boat conformations. Prove that the half-chair is the least stable of all conformations and twist- boat is more stable than the boat conformation. Provide the relevant drawings/structures.

Answer 1

Cyclopentane

Structure of Cyclopentane

Cyclopentane

Angle Strain in Cyclopentane

To achieve maximum stability, there is a deviation of the bond angle between the atoms in the molecule, from the ideal bond angle.In its flat structure it has ring strain and torsional strain. Ring Strain consists of no.of Angle Strain. The increase in the number of angle strain leads to instability.

The Ring Strain and Torsional Strain are the angle strain of cyclopentane.

Flat Structure of Cylopentane

| HK,

The bond angle is 108^o .

Eclipsed C-C bond(torsional strain)

The tortsional strain is of =10K Cal / mol

Structure for envelope conformation

Envelope Cyclopentane

Twist Conformation

Twist Cyclopentane

The Conformations above don't have perfect alternate C-C bonds

They have less torsional strain than Flattered one.

Cyclohexane

Structure of Cyclohexane

Cyclohexane

Flat Conformation of cyclohexane

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There is enormous torsional strain, because of too much strain in the flat structure. It is about 20KCal/mol. The C-C bond is eclipsed and also the angle strain is with internal angles 120^o and above the ideal angleof 109^o.

Chair Conformation of Cyclohexane

a KO He- Ha He He se Ha He Mad

It has Six axial(a) Hydrogen atoms and Six equatorial (e) Hydrogen atoms

Boat Conformation of Cyclohexane

AA H H

Flagpole Hydrogen

The flagpole bonds are represented as shaded portion. Hydrogen atoms present in the flagpole bonds are called flagpole hydrogens. Chair conformation of the cyclo hexane ring is more stable than boat conformation of the cyclohexane ring.

half chair conformation

twist boat conformation

due to maximum strain it is least stable. it is 10 calory less stable