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090			_aB-10326
245	1	0	_aEnzymatic Ring-Opening Polymerization of Lactones by Lipase Catalyst: Mechanistic Aspects
490	0		_vMacromol. Symp., 240, p.178-185, 2006
520	3		_aMechanistic aspects of lipase-catalyzed ring-opening polymerization (ROP)of lactones to give polyesters are discussed from accumulated experimental data and new insight. Comparison of the ROP reactivity by lipase catalyst with the anionic ROP reactivity by a metal-catalyst clearly demonstrates the characteristics of lipase catalysis; the larger ring-sized monomers with lower ring strain showed higher polymerizability than medium ring-sized ones, in contrast to the anionic ROP showing the reverse direction where the ring strain of monomer is operative. The enzyme-catalysis involves an acyl-enzyme intermediate formation as a key-step. From the copolymerization results a new mechanism is proposed, that involves the formation of the acyl-enzyme intermediate (acylation step)and/or the nucleophilic attack of the propagationg alcohol end to the carbonyl carbon of the intermediate to open the monomer ring (deacylation step)as the rate-determining step. The structure of the propagating alcohol end (primary or secondary)affects much on which step is more operative.
650	1	4	_aCATALYSIS
650	1	4	_aLACTONE
650	1	4	_aLIPASE ENZYME
650	1	4	_aREACTION MECHANISM
650	1	4	_aRING-OPENING POLYMERIZATION
700	1	2	_aKobayashi, S.
856	4	0	_uhttps://drive.google.com/file/d/1zzPia3QVtFd9XjF-PaYycrpG9S8NVfgI/view?usp=drivesdk _zPara ver el documento ingresa a Google con tu cuenta: @cicy.edu.mx
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