Which is more stable, cis- or trans- 1,3-di-(methylcarboxylate) cyclobutane ? Why?

Dear student

 

Cis isomer is mpre stable than trans form.

It is because cyclobutane looks like a square piece of paper with a fold along the diagonal. If you add the methyl groups to the corners not on the fold, they can be both axial or both equatorial. The axial is the less stable conformation than diequatorial. If it is the trans compound, then it will have one axial and one equatorial. Just as two equatorial groups are more stable, only one equatorial group will be less stable.