Reactivity neighboring group effect

Structure-reactivity relationships have also been developed for these isomerizations. For H abstraction from a CH3-X, CH2-XY, or CH-XYZ, respectively, through a 6-membered transition state, rate constants of 1.6 X 105, 1.6 X 10fl, and 4 X 106 s 1, respectively, are recommended (Atkinson, 1997a, 1997b). These are corrected for neighboring group effects using F(-CH3) = 1.0, F(-CH2-) =... 

Mechanism. The following types of evidence ere pertinent in selecting on acceptable mechanism for olefin epoxidation by means of peroxy acids (1) the nature of the peroxy acid and the electronic effect of eubBtituents on its reactivity (2) the electronic effect of substituents on the reactivity of the olefin component (3) stereochemical factors affecting the reactivity of the olefin (4) the possibility of acid dialysis (5) solvent effects and (6) neighboring group effects. 

The Troc group has a weaker neighbor group effect than the acetyl group. (Ether protected trichloroacetimidates are more reactive than... 

Further work on chemical structure and reactivity might well include an examination of the possibility of occurrence of an Amadori rearrangement in the case of the glycosyl ureides. In addition, studies of the tautomerism of glycosyl ureides under various conditions of pH and of the neighboring-group effect would be of value in the interpretation of many of the seemingly unorthodox chemical reactions of these compounds. 

Use of acetal/ketal monomers with reactive polymerizable functionality allows easier access to families of related polyacetals. This facilitates determination of structure-activity correlations that influence many properties including hydrolysis half-life. Hydrolytic stability is often a function of whether the degradable unit is a ketal or acetal, along with other features of the polymer structure (e.g., hydrophilicity or neighboring group effects). The use of a polymerizable bis-diene Michael acceptor as an A-A mono-... 

The reactivity of macromolecular and low-molar-mass groups is about the same when neighboring group effects are taken into consideration. 

If there is only a small number of reactive groups per macromolecule, the environment of these groups is not changed as the reaction proceeds. The macromolecular chain simply acts as a diluent. Of course, neighboring group effects can also play a role, especially if five- and six-membered cyclic transition states can be formed. An example of this is the partial imidization of poly(methacrylamide) at temperatures above 65°C ... 

A neighboring group effect is considered as a localized phenomenon operating on a few atoms in the vicinity of each reactive group. 

Abstract The structure/reactivity behavior for pure hydrocarbon diene monomers, and for dienes containing heteroatoms has been examined. Steric hindrance is the controlling factor for hydrocarbon monomers, and intramolecular electronic interactions determine the reactivity of dienes possessing heteroatom functionality. This electronic interaction phenomenon is termed the "Negative Neighboring Group Effect". 

In principle, the reactivity of a functional group should not be altered when it is attached to a polymer ( 1). However, special effects may be encountered when a reagent is attracted to a polymer or repelled from it, when the polymer-bound reactive group is activated or inhibited by a neighboring group or when the local polarity of the polymer domain differs from that of the bulk solvent. A review of studies of such effects... 

---