Adsorbed methyl, chain initiation

Figure 8 Simulated adsorption by molecular dynamics of (A) poly (p-phenylene) oxide (PRO), (B) poly(methyl-l,4-phenylene) (PMP) and (C) poly(iso-propyl-l,4-phenylene) (PIPP) on an alumina surface showing substantial structural changes during the adsorption process (upper figure initial conformation lower figure = adsorbed conformation) (From Ref. 71.) Note the formation or absence of adsorption loops in the polymer chains for the different cases.

Methyl acetate synthesis rate does not depend on DME pressure, but increases linearly with CO pressure up to 10 atm. This kinetic response is consistent with a sequence of elementary steps (Fig. 6) involving the formation of surface methyl groups at Brpnsted acid sites initially via direct DME reactions with protons and then via chain transfer reactions (propagation steps) of DME with surface acetyls formed via rate-determining CO insertion into C-0 bonds in methyl groups at the catal3rtic steady state (92). CO insertion occurs from the gas phase or via weakly held CO species adsorbed noncompetitively with CH3 groups. 

FIGURE 8.2 Cyanoacrylate monomer units polymerize in a join by an anionic mechanism, typically initiated by hydroxyl groups in adsorbed water. The alkyl (-R) group can be varied to modify the polymer properties. R may be methyl, ethyl or butyl, or contain an unsaturated group allowing cross-linking between chains and thus greater stability. 

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