Baeyer strain energy

Note Bond path angles / are used for bent bonds. According to Hooke s law, the Baeyer strain energy is 41.3 kcalmoT1 anharmonicity effects lead to another 5 kcal moT1 ... 

The smaller bond angles prevent normal overlap along the intemuclear axis (dotted line). Overlap occurs outside the intemuclear axis and a bent bond is formed (also referred to as a r bond). The r bond is weaker than a a bond due to nonoptimal overlap and thus is of higher energy. This type of strain is termed angle strain (sometimes called Baeyer strain). It comes about because normal bond angles are not possible and thus nonoptimal overlap results. Angle strain... 

Comparison of the heats of combustion of cycloalkanes (Table 9.1) shows that cyclopropane, cyclobutane, and cyclononane yield more energy per methylene group than the other cycloalkanes. This can be attributed to strain resulting from bond-angle distortion (Baeyer strain), eclipsed conformations (Pitzer strain), and trans-annular, repulsive van der Waals interactions. Common (five- and six-membered) rings and large (more than twelve-membered) rings have little or no strain. This... 

Baeyer 1885 Molecules are analogous to hard spheres connected together by springs which may contain strain energy... 

The molecular conformations induced by relief of Baeyer strain and Pitzer strain are reflected in the energy required for intramolecular cyclization reactions to form each ring. As two reactive ends of the acyclic fragment come together, the strain inherent to the ring product becomes important (see sec. 6.6.B.i). In other... 

The experimental data in Table 3.1 show that the calculated values of total angle strain are approximately correct only for cyclopropane, cyclobutane, and cyclopentane. Cyclohexane is definitely not the strained compound Baeyer s theory predicts, and the larger ring compounds are also not very strained. Any chemist today can explain the discrepancy between these calculated and experimental values of strain energy cyclohexane is not planar. In either the chair or boat conformations (Figure 3.12), all bond angles can be approximately 109.5°. In the chair conformation of cyclohexane, all bonds are staggered, and there are no apparent van der Waals repulsions in the molecule. ... 

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