In a
molecule, strain energy is released when the constituent
atoms are allowed to rearrange themselves in a chemical reaction. The external work done on an elastic member in causing it to distort from its unstressed state is transformed into strain energy which is a form of potential energy. The strain energy in the form of elastic deformation is mostly recoverable in the form of mechanical work. For example, the
heat of combustion of
cyclopropane (696 kJ/mol) is higher than that of
propane (657 kJ/mol) for each additional
CH2 unit. Compounds with unusually large strain energy include
tetrahedranes,
propellanes,
cubane-type clusters,
fenestranes and
cyclophanes. ==References==