Question

1. Why is dimethylcyclopentane more stable than dimethycyclohexane?

2. what is the external pressure needed for 100 mm Hg at 25 degrees celcius.

Answer 1

1.Dimethylcyclopentane exists primarily in ring form and dimethylcyclohexane exist in chair or boat form.The stability apparently can be presume to be more of cyclohexane due to strain considerations

However cyclopentane has the ability to buckle the ring and push one carbon atom out of the plane and hence reduce strain on the planar structure increasing its stability.

2.Pressure of Hg at room temparature=100mm=133.33 Pa

=0.1333bar.

Temparature=298kelvin

Vapour pressure of Hg at room temparature=0.0024bar=1.82millimetre

External pressure required=0.1333bar-0.0024 bar=0.1309bar=0.129atm