alkenes are subject to strain resulting from distortion of the sp²-hybridized carbon centers. Illustrative is C₆₀ where the carbon centres are pyramidalized. This distortion enhances the reactivity of this molecule. Angle strain also is the basis of Bredt's rule which dictates that bridgehead carbon centers are not incorporated in alkenes because the resulting alkene would be subject to extreme angle strain.

Small trans-cycloalkenes