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Ring-Chain Interconversion

Colquhoum, H. M. Lewis, D. E Ben-Haida, A. Hodge, P. Ring-chain interconversion in high-performance polymer system. 2. Ring-opening polmerization-copolyetherification in the synthesis of aromatic poly(ether sulfones). Macromolecules 2003, 36, 3775-3778. [Pg.260]

Mw of 73 000 (Scheme 55) [229]. Colquhoun and coworkers also reported a ring-chain interconversion system in poly(m-phenylene isophthalamide) (Nomex) [230]. Cyclodepolymerization was best achieved by treating a solution of the polymer in DMSO containing CaCl2 or IiCl as a solubilizing... [Pg.37]

Kt = 0.84 and at pH 7, KT = 0.36. The rate of ring-chain interconversions obtained from temperature-jump kinetic experiments appears to be hydro-nium-ion-catalyzed in the pH range 11.5-13, with rate constants reaching about 105 s 1. It was presumed that the cyclic tautomers 54 can serve as kinetically competent intermediates for transimination sequences at the active sites of pyridoxal-P-dependent enzymes. [Pg.25]

B. Colour Changes Caused by Ring-Chain Interconversions. 452... [Pg.441]

A prominent example for colour changes due to ring/chain interconversions is the methylarsenic system. (MeAs), is yellow in all phases but polymerizes with formation of a purple-black ladder polymer (equation 9). [Pg.452]

The key compound on the way to the debranched nagstatin 175 has been synthesized from the L-ribose derivative 176 by employing ring-chain interconversion involving addition of trityl imidazole, selective sulfonylation, and warm acetylation which causes detritylation with cyclization [139] (O Scheme 42). [Pg.401]

This discussion deals with the poly and meta acids and their derivatives made by heating appropriate combinations of reactants to form a melt or a labile solid composition from which the desired product crystallizes. Such labile solid compositions often include an amorphous phase, plasticized by water, in which ring-ring and ring-chain interconversions take place. ... [Pg.232]

N-Methyl-tetrahydro-l,3-oxazine exists as a mixture of ring and open-chain tautomers in TFA the analogous oxazolidine behaves similarly. Of interest is the fact that ring-chain interconversion is more rapid for the oxazolidine, in converse to the predictions of Baldwin s vectorial rules. [Pg.274]

H. M. Colquhoun, D. F. Lewis, P. Hodge, A. Ben-Haida, D. J. Williams, and I. Baxter. Ring-chain interconversion in high-performance polymer systems. 1. [poly(oxy-4,4 -biphenyleneoxy-1,4-phenylenesulfony 1-1,4-phenyl-ene)] (Radel-R). Macromolecules, 35 6875-6882, 2002. [Pg.281]

Ben-Haida A, Williams DJ, Baxter I, et al. Ring-chain interconversion in... [Pg.208]

Hodge P. Ring-chain interconversion in high-performance polymer systems. 2. [Pg.208]

From the formal equilibria for ring-chain interconversions (eqns [2]-[7]), we also get equations for the ring-ring equilibria. [Pg.35]

The chain-ring equilibria are often observed in systems of polyamides. Independently of the route of preparation of polymers (polycondensation, polymerization of lactams, or other cyclic amides, including cyclic oligomers) the ring-chain interconversions are often important and cannot be neglected. However, the equilibrium conditions usually are not reached and often only kinetic distributions can be observed. [Pg.45]

When the reaction routes leading to macrocyclization are available, the real equilibrium requires equilibration of the ring-chain interconversions (cf Scheme 1) as well. [Pg.51]


See other pages where Ring-Chain Interconversion is mentioned: [Pg.268]    [Pg.590]    [Pg.590]    [Pg.273]    [Pg.279]    [Pg.279]    [Pg.279]    [Pg.590]    [Pg.102]    [Pg.103]    [Pg.104]    [Pg.105]    [Pg.169]    [Pg.169]    [Pg.170]    [Pg.170]   


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Chain-ring interconversions

Chain-ring interconversions

Ring interconversions

Ring, chain

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