Monomeric analog

Deligoz and Yilmaz [52] reported that the selective liquid-liquid extraction of various alkali and transition metal cations from the aqueous phase to the organic phase as carried out by using p-tert-h iy calix[4]arene (1), p-tert-b x. y calix[6]arene (2), tetra-ethyl-p-tm-butylcalix[4]arene-tetra-acetate (3), tetra-methyl-p-/< /-/-butyl calix[4]arene-tetraketone (4), calix[n]arenes ( = 4 and 6) bearing oxime groups on the lower rim (5 and 6) and a polymeric calix(4]arene (8). It was found that compounds 5 and 6 showed selectivity towards Ag, Hg, Hg, Cu, and Cr and the order of the ex-tractability was Hg > Hg > Ag > Cu > Cr. The polymeric calix[4]arene (8) was selective for Ag, Hg, and Hg , unlike its monomeric analog. 

The asymmetric ring opening (ARO) of racemic terminal epoxides with H2O via hydrolytic kinetic resolution provides an efficient synthetic route to prepare optically pure terminal epoxides. The dimeric type chiral Co(salen)AlX3 complex has great potential to catalyze HKR of terminal epoxides in a highly reactive and enantioselective manner in comparison to their monomeric analogy. 

Kinetic Studies. The pioneering work of Hierl et al. (8) and Delaney et al. (9) had established that hydrolysis of jr-nitro-phenylcarboxylates was an excellent means of observing the nucleophilic catalysis by 4-(dialkylamino) pyridine functionalized polymers. Hydrolysis of p-nitrophenylacetate in a buffer at pH 8.5 showed that the polymer was a slightly better catalyst than the monomeric analog PPY (Table II). However, preliminary results indicate that the polymer bound 4-(dialkylamino) pyridine is more effective as a catalyst than the monomeric analog in the hydrolysis of longer carbon chain p-nitrophenylcarboxylates, such as p-nitrophenylcaproate. 

It was noted early in our studies of monomeric analogs of I that significant changes occurred in the visible spectrum upon conversion between oxidation states changes which translate into vivid, visual differences in color. These differences in color are also very apparent in poly-I and thus make it of interest as an e 1 ectrochromic material (61. 

Polymers of 4(5)-vinylimidazole and copolymers containing this monomer are usually studied with ethanol-buffer mixtures as solvent because of their insolubility in water. Overberger and Smith (82) found that poly(l-Me-5-vinylimidazole) was soluble in water. Negatively charged substrates with long apolar side chains were bound very strongly to this polymer. A rate enhancement of 106 over the monomeric analog, 1,5-dimethylimidazole, was observed. 

The oxamate group has been incorporated into a vinyl polymer by Kirsh and Kabanov 41). These workers prepared a copolymer of 4-vinyl-A -(phenacyloxime)pyridinium bromide and vinylpyridine. For the hydrolysis of p-nitrophenyl acetate the oxamate polymer produced a significant rate enhancement over the monomeric analogs. 

The naturally occurring compounds in the flavan, flavan-3-ol, flavan-4-ol, flavan-3,4-diol, and proanthocyanidin classes, together with their plant sources, are listed in Table 11.2-Table 11.17. The lists are confined to new compounds reported in the post-1992 period or those that have been overlooked in the 1994 review, and therefore must be considered in conjunction with the corresponding tables of the Porter reviews to be comprehensive. Since many of the monomeric analogs have been published under trivial names these will be retained to facilitate electronic literature searches. Unfortunately, a considerable number of these potentially chiral compounds have been reported without assignment of absolute configuration, and are hence presented as such. 

Originality Poly(dithienylbenzo[l,2-b 4,5-b ]dithiophene) and monomeric analogs... 

The local chemical environment of the polymer-metal complex can be considered to be fairly different from ihat of the monomeric analog due to the effect of the polymer chain and the neighboring groups, even if part of the complex is the same in both. 

In the case of the heat of fusion of 6-6, and 6-10 Nylon, Wilhoit and Dole (1953) studied the monomeric analogs N,N1-n-hexyl adipamide, N.lSP-n-hexyl sebacamide and N.N -n-propyl adipamide obtaining 31.2,... 

In the case of the polyesters Smith and Dole s (1956) study of the monomeric analogs of polyethylene terephthalate, namely, dimethyl and diethyl terephthalate, in which they found 39.5 and 26.6 cal g-1 for the heats of fusion, respt., was of aid in supporting their conclusion that Edgar and Hill s (1952) estimate of the heat of fusion of polyethylene terephthalate from the use of the copolymer Eq. (6), namely 11.5 cal g-1, must be definitely too low. It should be pointed out that Edgar and Hill were also uncertain as to the correctness of the value 11.5 cal g-1. 

If the nucleus senses another metal ion with a different Am value, then the total shift will be given by the sum of two terms of the type of Eq. (6.9), each containing its own Am and C, values. Ami and Ami can be estimated from the monomeric analogs. The C, i and C,-2 values can be calculated once and for all for each system with (he help of Hamiltonian Eq. (6.3). Their values are reported in Table 6.1 for dimers involving 5, and 52 values from xh to 1k [3], These coefficients can be calculated from the following equations ... 

Iron porphyrin dimers, iron(III) /a-oxodimcr iron(III) porphyrin, for example, are used as biomimetic models of oxidation catalysts [98], It is shown that [Fe(TFPP)]20 and other modifications regioselectively oxidize adamantane and cyclohexane in the presence of iodosylbenzene (PhIO). Comparison of these results with corresponding monomeric analogs indicates the efficiency of the FeP dimer at the level of the monomeric one. 

The Michaelis-Menten kinetics were similarly observed for water-soluble co-pcdymers containing BI or PI units in the solvolysis of p-acetoxybenzoic acid (ABA) 19 (71). btterestingly, the monomeric analogs, AcBI22 and AcPI 23, do not produce substrate binding under die same condition. However, the Michaelis-Menten... 

The catalytic effects of poly(3-methyl-l-vinylimidazolium iodide) poly(3-n-hexadecyl-l-vinylimidazolium iodide), and their monomeric analogs on the alkaline hydrolysis of a series of neutral and anionic nitro-phenyl esters were studied in order to elucidate the contribution of hydrophobic and electrostatic interactions to their esterolytic efficiency. 

Reetz et al.59 have introduced polypropylenimine (PPI) dendrimers as the core for building phosphine-coated constructs that can complex with Rh(COD) BF4, where COD = 1,5-cyclooctadiene, to instill the desired catalytic character. Hydroformylation of 1-octene with these metallodendrimers was shown to have turnover numbers that were comparable to those of monomeric analogs. It was pointed out that these catalysts could be easily recovered by means of membrane separation technology.60 Gong et al. have used water-soluble, phosphonated dendritic... 

Polyvinylimidazoles show some enhanced reactivities toward simpte phenyl esters relative to monomeric analogs, caused by possible multifimctiraial catalysis and by substrate attraction due to secondary valence forces. Remarkable rate enhancements were found when long-chain substrates were used, and this was attributed to increased hydrophobic interactions. The catalytic property of imidazole polymers can be con-sider ly modified by the use of appropriate comonomers. Thus, Michaelis-Menten kinetics were observed for simple substrates by increasing hydrophobicity of the catalytic site. Combinations of hydrophobic and electrostatic interactions at the catalytic site produced further increases in the catalytic efficiency. It was pointed out that Qie composition and conformation of catal3rst polymers are related to the multifunctionality and microenvironments of the catalytic site. 

The effect of rifamycin dimers on the activities of nucleic acid polymerases from various sources were tested and it was found that the chemical dimers of rifamycin SV (3) resembled the corresponding monomeric analogs with respect to their inhibitory properties vs. the nucleic acid polymerases [223]. 

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