Question

Substituted cyclobutadiene derivatives with bulky alkyl groups are easier to isolate instead of

unsubstituted cyclobutadiene. Do you find any reason behind?

Answer 1

Unsubstituted cyclobutadiene is prone to dimerization, so it is very difficult to isolate it in its pure form. The presence of bulk substituents, such as tert-butyl, prevents dimerization due to steric complications.