page_title: Strain (chemistry)
section_title: Van der Waals strain
hierarchical_section_title: Strain (chemistry) / Kinds of strain / Van der Waals strain
caption_attribution_description: English: Reaction of trialkylamines with methylbromine
context_page_description: In chemistry, a molecule experiences strain when its chemical structure undergoes some stress which raises its internal energy in comparison to a strain-free reference compound. The internal energy of a molecule consists of all the energy stored within it. A strained molecule has an additional amount of internal energy which an unstrained molecule does not. This extra internal energy, or strain energy, can be likened to a compressed spring. Much like a compressed spring must be held in place to prevent release of its potential energy, a molecule can be held in an energetically unfavorable conformation by the bonds within that molecule. Without the bonds holding the conformation in place, the strain energy would be released.
context_section_description: Van der Waals strain, or steric strain, occurs when atoms are forced to get closer than their Van der Waals radii allow.  Specifically, Van der Waals strain is considered a form of strain where the interacting atoms are at least four bonds away from each other. The amount on steric strain in similar molecules is dependent on the size of the interacting groups; bulky tert-butyl groups take up much more space than methyl groups and often experience greater steric interactions.
  The effects of steric strain in the reaction of trialkylamines and trimethylboron were studied by Nobel laureate Herbert C. Brown et al.  They found that as the size of the alkyl groups on the amine were increased, the equilibrium constant decreased as well.  The shift in equilibrium was attributed to steric strain between the alkyl groups of the amine and the methyl groups on boron.
caption: Reaction of trialkylamines and trimethylboron.
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