Why 1 st is stable than 3rd ????????

ethyl group is more bulky than methyl so 1is more stable than 3

ethyl group is more bulky than methyl so 1is more stable than 3

-C2H5 is bulkier than -CH3 .

1st is stable than 3rd as In 3rd bulky ethyl group is at axial position and in 1st ethyl group is at equatorial position....And the conformation is most stable if bulky group is pr...

Because here Ethyl group is more bulky that methyl so it will prefer on equatorial position rather than axial so I>III