Anchimeric Assistance (Neighboring Group Participation). The participation of neighboring groups in an SN reaction is revealed by unique stereochemical. Intramolecular reactions, nucleophilic catalysis, anchimeric assistance, epoxide synthesis, Payne rearrangement. Download Citation on ResearchGate | Some Factors that Influence Anchimeric Assistance | It is obvious that a number of requirements are necessary for.
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Anchimeric Assistance – Chemistry LibreTexts
Ryan Spoering on March 11, Consider the reaction below. The I – initiates a nucleophilic attack on the carbon to which the Cl is bound, thus replacing it. The I is then much more vulnerable to replacement by the acetyl group.
Similar phenomena as above can occur on an intramolecular level. Anchimeric assistance is when a neighboring group participates in a reaction.
Anxhimeric the following reaction rate data for these molecules reacting with AcO. Molecules 2 and 3 are slower than 1 because of an electron withdrawing effect. Molecules 4 and 5 are much faster because the chain is long enough to allow anchimeric assistance, where the molecule can circularize. Mustards are a class of powerful aklylating agents, such as mustard gas.
These destroy tissue by alkylating everything.
In general, alkylating agents are bad for assistaance – they react with all the weak nucleophiles floating around assistanec cells. While mustard gas is an extreme example, other alkylating agents cause DNA damage and are associated with cancer. Another example of anchimeric assistance is the reason why the second of these two reactions is faster, and creates a racemic mixture:.
The mechanism for the second reaction involves an intermediate that has a resonance structure, thus losing the stereochemistry of the reactant:.
This is actually a poor way to make epoxides, because the synthesis of the original molecule is not easy. The two epoxides being made above could be made from trans and cis butene respectively. The more substituted an epoxide is, the more stable it is.
This particular reaction is reversible, but the product is somewhat favored anchumeric the reactant because the epoxide is triply substituted rather than doubly substituted.
Another example is this reaction, where the sulfur can only attack once the epoxides have rearranged themselves:. Eric Vallabh Minikel is on a lifelong quest to cure human prion disease.
30.4: Anchimeric Assistance
Intramolecular reactions Nucleophilic catalysis Consider the reaction below. In essence, the iodine lowers the activation energy.
Anchimeric assistance Similar phenomena as above snchimeric occur on an intramolecular level. Another example of anchimeric assistance is the reason why the second of these two reactions is faster, and creates a racemic mixture: The mechanism for the second reaction involves an intermediate that has a resonance structure, thus losing the stereochemistry of the reactant: Epoxide synthesis This is actually a poor way to make epoxides, because the assustance of the original molecule is not easy.
Payne rearrangement Here is an example: Another example is this reaction, where the sulfur can only attack once the epoxides have rearranged themselves: