Negative neighboring group effects

Other groups such as esters, silylethers, and imides are also successfully incorporated through ADMET depolymerization with 14 (Fig. 8.21).49 For an ester functionality, at least two methylene spacer units must be present between die olefin site and die functional group in order to achieve depolymerization. This is due to die negative neighboring group effect, a deactivation of the catalyst by coordination of the functionality heteroatoms to die catalyst.50 By physically... 

Imide-terminated telechelics are also synthesized by metathesis depolymerization, and it is found that phthalimide-substituted olefins allow for productive depolymerization when only one methylene spacer separates the nitrogen atom and the olefin (Fig. 8.21). This combination of steric hindrance around the nitrogen lone pair and decreased electron donation from resonance prevents the negative neighboring group effect. However, secondary acyclic amines are unable to produce telechelics through metathesis depolymerization because of unfavorable catalyst-amine interactions. 

Negative neighboring group effect, 456 Network formation, 13 Networks. See also Epoxy-phenol networks Phenohc networks phenolic-based, 376 polyester-based, 58-60 Neutral hydrolysis, 564-565... 

Keywords Acyclic diene metathesis polymerization, ADMET, Condensation polymerization Functionalized polymers, Negative neighboring group effect, Branched polyethylene... 

Wagener, K.B. Brzezinska, K. Anderson, J.D. Younkin, T.R. Steppe, K. DeBoer, W. Kinetics of Acyclic Diene Metathesis (ADMET) Polymerization Influence of the Negative Neighboring Group Effect. Macromolecules 1997,30,7363-7369. 

Figure 6. Schematic of the negative neighboring group effect.

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". 

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