Complex sentence: The second example of a dioxetane was made shortly after: the symmetrical compound 3,3,4,4-tetramethyl-1,2-dioxetane, obtained as pale yellow crystals that sublimed even when kept in the refrigerator.
Split into simpler sentences: The second example of a dioxetane was made shortly after. This could be obtained as pale yellow crystals that sublimed even when kept in the refrigerator.