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MOLECULARITY - 2 reference results
Molecularity
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Molecularity
Molecularity in chemistry is the number of colliding molecular entities that are involved in a single reaction step. While the order of a reaction is derived experimentally, the molecularity is a theoretical concept and can only be applied to elementary reactions. In elementary reactions, the reaction order, the molecularity and the stoichiometric coefficient are the same, although only numerically, because they are different concepts.

  • A reaction involving one molecular entity is called unimolecular.
  • A reaction involving two molecular entities is called bimolecular.
  • A reaction involving three molecular entities is called termolecular. Termolecular reactions in solutions or gas mixtures are very rare, because of the improbability of three molecular entities simultaneously colliding . However the term termolecular is also used to refer to three body association reactions of the type:

A + B overset{M}{to} C
Where the M over the arrow denotes that to conserve energy and momentum a second reaction with a third body is required. After the initial bimolecular collision of A and B an energetically excited reaction intermediate is formed, then, it collides with a M body, in a second bimolecular reaction, transferring the excess energy to it.

The reaction can be explained as two consecutive reactions:

A + B to AB^*
AB^* + M to C + M

These reactions frequently have a pressure and temperature dependence region of transition between second and third order kinetics.

Notes and references

See also

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Molecularity
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molecularity
Jan 01, 2004; molecularity The number of molecules involved in forming the activated complex in a step of a chemical reaction. Reactions are...
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bimolecular reaction
Jan 01, 2004; bimolecular reaction A step in a chemical reaction that involves two molecules. See molecularity .
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Research results from Texas A&M University update knowledge of inorganic chemistry.
Aug 18, 2008; Three new phosphonic acid ligands (4-(t)butylphenyl phosphonic acid, 3,5-dimethylphenyl phosphonic acid, and...
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Studies from University of Waterloo, Department of Chemistry provide new data on life sciences.
Oct 14, 2008; Data detailed in 'Conformational stability and folding mechanisms of dimeric proteins' have been presented. According to recent...
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Studies from G. Vamosi et al further understanding of physical chemistry.
Dec 05, 2008; According to a study from Debrecen, Hungary, The thermal denaturation of immobile four-way DNA Holliday junctions with 17 base...
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