Strain energy

 ( Chemical Bonding ) 

In physics, the elastic potential energy gained by a wire during elongation with a tensile (stretching) or compressive (contractile) force is called strain energy. For linearly elastic materials, strain energy is:

$U\; =\; \backslash frac\; 1\; 2\; V\; \backslash sigma\; \backslash varepsilon\; =\; \backslash frac\; 1\; 2\; V\; E\; \backslash varepsilon^2\; =\; \backslash frac\; 1\; 2\; \backslash frac\; V\; E\; \backslash sigma^2$

where is stress, is strain, is volume, and is Young's modulus:

$E\; =\; \backslash frac\; \backslash sigma\; \backslash varepsilon$

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Molecular strain In a molecule, strain energy is released when the constituent atoms are allowed to rearrange themselves in a chemical reaction. March's Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, Michael B. Smith & Jerry March, Wiley-Interscience, 5th edition, 2001, 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 methylene bridge. Compounds with unusually large strain energy include , , cubane-type clusters, and .

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