Chemistry - STEREO ISOMERISM Question with Solution | TestHub

I is anti ($\mathrm{C}{\mathrm{H}}_3-\mathrm{C}-\mathrm{C}-\mathrm{C}{\mathrm{H}}_3$ dihedral 180°) : no eclipsing, no gauche strain - lowest energy. III is gauche (staggered, but one $\mathrm{C}{\mathrm{H}}_3\leftrightarrow \mathrm{C}{\mathrm{H}}_3$ gauche interaction) - next. IV is partially eclipsed (two $\mathrm{C}{\mathrm{H}}_3\leftrightarrow \mathrm{H}$ eclipses and one H↔H eclipse). II is fully eclipsed with $\mathrm{C}{\mathrm{H}}_3$ eclipsing $\mathrm{C}{\mathrm{H}}_3$ - the highest energy. Hence I $<$ III $<$ IV $<$ II.