Alicyclic compounds : Preparations of cyclo alkanes, Bayer strain theory and
orbital picture of angle strain.
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Bayer strain theory, also known as the Baeyer strain theory or Baeyer strain hypothesis, is a concept in organic chemistry proposed by German chemist Adolf von Baeyer in the late 19th century. It explains the relative stability and reactivity of cyclic compounds based on the strain or distortion present in their molecular structures.
According to Bayer strain theory, cyclic compounds experience strain due to deviations from the ideal bond angles and bond lengths found in acyclic (straight-chain) compounds. This strain arises from two main factors: angle strain and torsional strain.
- Angle Strain: Angle strain refers to the strain caused by the deviation from the ideal bond angles in a cyclic compound. In an ideal cycloalkane, all bond angles would be 109.5 degrees (tetrahedral angle). However, in small cycloalkanes, such as cyclopropane or cyclobutane, the bond angles deviate significantly from this ideal value. For example, in cyclopropane, the bond angles are approximately 60 degrees, causing significant angle strain.
- Torsional Strain: Torsional strain arises from the repulsive interactions between electron clouds of atoms or groups in a cyclic compound. When adjacent carbon atoms in a cyclic compound have bulky substituents or multiple substituents, the electron clouds can come into close proximity, resulting in repulsive interactions. This strain is most pronounced in cyclic compounds with eclipsed conformations, where the torsional strain is maximized.
The presence of angle strain and torsional strain leads to increased potential energy in cyclic compounds compared to their acyclic counterparts. As a result, cyclic compounds tend to be less stable and more reactive than their acyclic counterparts.
Baeyer strain theory also provides insights into the reactivity of cyclic compounds. Due to the strain present, cyclic compounds are more prone to undergo reactions that relieve the strain and increase their stability. For example, small cyclic compounds, such as cyclopropane or cyclobutane, readily undergo ring-opening reactions or participate in reactions that break the cyclic structure to alleviate the strain.
Baeyer strain theory has been instrumental in understanding the properties and reactivity of cyclic compounds. It helps explain the preference for larger ring sizes in terms of reduced strain and increased stability. The concept of strain in cyclic compounds has further implications in organic synthesis, as it guides chemists in designing strategies to overcome or utilize strain in the synthesis of complex molecules.
Overall, Bayer strain theory provides a valuable framework for understanding the relationship between the structure, stability, and reactivity of cyclic compounds based on the strain they experience.
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