Ring Strain
According to the VSEPR theory of molecular bonding, the preferred geometry of a molecule is that in which both bonding and non-bonding electrons are as far apart as possible. In molecules, it is quite common for these angles to be somewhat compressed or expanded compared to their optimal value. This strain is referred to as angle strain, or Baeyer strain. The simplest examples of angle strain are small cycloalkanes such as cyclopropane and cyclobutane, which are discussed below. Furthermore, there is often eclipsing in cyclic systems which cannot be relieved.
| Ring size | Strain energy (kcal/mol) | Ring size | Strain energy (kcal/mol) | |
|---|---|---|---|---|
| 3 | 27.5 | 10 | 12.4 | |
| 4 | 26.3 | 11 | 11.3 | |
| 5 | 6.2 | 12 | 4.1 | |
| 6 | 0.1 | 13 | 5.2 | |
| 7 | 6.2 | 14 | 1.9 | |
| 8 | 9.7 | 15 | 1.9 | |
| 9 | 12.6 | 16 | 2.0 |
In principle, angle strain can occur in acyclic compounds, but the phenomenon is rare.
Read more about this topic: Strain (chemistry), Kinds of Strain
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