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The replacement of all hydrogen atoms of Zn

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High‐pressure ethene polymerizations using thirteen tert‐alkyl peroxyester initiators, RC(CH3)2OOCOR′ (with R = methyl, ethyl, neo‐pentyl, tert‐butyl and R′ = methyl, i‐propyl, propyl, butyl, tert‐butyl, 2‐heptyl) have been carried out in a CSTR. The initiator efficiency f has been determined for each peroxyester at 2 000 bar over a range of temperatures, partly up to 250 °C. The highest initiator efficiencies, up to about f = 0.9, are observed for tert‐butyl peroxyesters, in which the R' species is a primary radical, as e.g., with tert‐butyl peroxypentanoate and tert‐butyl peroxyacetate. The lowest efficiency value, of about f = 0.37, occurs with tert‐butyl peroxypivalate. The radicals from initiator decomposition, R′COO· and RC(CH3)2O., may undergo β‐scission reactions to produce R′ radicals by decarboxylation and R radicals by “deacetonization”, respectively. In‐cage termination reactions between oxygen‐centered and carbon‐centered radicals essentially control initiator efficiency.magnified image

Abstract.[Cd(CsHs)2(CsHsN)2], Mr= 400"80, monoclinic,