Grubbs Ring Opening Metathesis Mechanism

Grubbs Ring Opening Metathesis Mechanism-62
The cycle strain energy of most cycloalkenes is more than 20 k J/mole.

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The listed side reactions, eventually, lead to a broadening of the molecular mass distribution (MMD) and a decrease in a molecular weight of the polymer [10].

The chain transfer as well as the spontaneous termination of the growing chain is highly improbable, so ROMP is a living polymerization.

Catalytic systems were mixtures of various compounds containing a transition metal.

For example, in the late 1960s, Calderon and Goodyear employees published a number of papers about usage of a catalyst consisting of WCl, and ethanol [12, 13].

Ethyl vinyl ether is an effective stopper for most ruthenium catalysts.

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It forms a very stable complex of the [Ru]=CHOEt type and ensures the functionalization of the polymer end-group.The strain energy of the cycle releasing during the decomposition of the metal-cyclobutane complex and maintaining the forward direction of the reaction.However, if the deformation energy of cycle is low, the contribution of the entropy factor into the Gibbs energy becomes more significant in comparison with a smaller enthalpy factor.In the history of metathesis, catalytic complexes with a well-studied structure were called “well-defined” catalysts.The discovery of “well-defined” catalysts had significantly increased the ability of ROMP to obtain polymers that have unique properties.The next step is a formation of a metal-cyclobutane intermediate.This process occurs in each act of addition of the monomer during the chain growth.In this case, the entropy factor must be properly reduced in order to implement the direct process by increasing the monomer concentration or decreasing the temperature of the process [9].Secondary metathesis reactions can occur in addition to the main described reactions during the polymerization process.Acrylate derivatives of 2-butene-1,4-diol, succinic anhydride or butyl acrylate can also stop the growth of the macromolecule [6].ROMP, as well as most metathesis reactions, is reversible, so the described transformations can proceed both in the forward and backward directions.

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