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Van der Waals strain is strain resulting from Van der Waals repulsion when two substituents in a molecule approach each other with a distance less than the sum of their Van der Waals radii. Van der Waals strain is also called Van der Waals repulsion and is related to steric hindrance . [ 1 ]
The strain energy of cyclopropane and cyclobutane are 27.5 and 26.3 kcal mol −1, respectively. [1] Cyclopentane experiences much less strain, mainly due to torsional strain from eclipsed hydrogens: its preferred conformations interconvert by a process called pseudorotation. [4]: 14 Ring strain can be considerably higher in bicyclic systems.
Ring strain theory was first developed by German chemist Adolf von Bayer in 1890. Previously, the only bonds believed to exist were torsional and steric; however, Bayer's theory became based on the interactions between the two strains. Bayer's theory was based on the assumption that ringed compounds were flat.
Steric hindrance is a consequence of steric effects. Steric hindrance is the slowing of chemical reactions due to steric bulk. It is usually manifested in intermolecular reactions, whereas discussion of steric effects often focus on intramolecular interactions. Steric hindrance is often exploited to control selectivity, such as slowing unwanted ...
The interaction between the two flagpole hydrogens, in particular, generates steric strain. Torsional strain also exists between the C2–C3 and C5–C6 bonds (carbon number 1 is one of the two on a mirror plane), which are eclipsed — that is, these two bonds are parallel one to the other across a mirror plane. Because of this strain, the ...
Torsional strain may refer to: Deformation (mechanics) Strain (chemistry)#Torsional strain This page was last edited on 30 December 2019, at 16:50 (UTC). Text is ...
However, because context will have an effect on steric interactions [7] some E s values can be larger or smaller than expected. For example, the value for phenyl is much larger than that for tert-butyl. When comparing these groups using another measure of steric bulk, axial strain values, the tert-butyl group is larger. [8]
The chair conformation minimizes both angle strain and torsional strain by having all carbon-carbon bonds at 110.9° and all hydrogens staggered from one another. [2] The conformational changes that occur in a cyclohexane ring flip take place over several stages. Structure D (10.8 kcal/mol) is the highest energy transition state of the process.