Initiator, 1,5-pentanediol

In this model, the intermediacy of a monomeric zinc species is postulated. To support this assumption, an examination of the effect of stoichiometry and solvent in cyclopropanation involving the 2,4-pentanediol auxiliary was preformed [59]. In the initial reaction protocol, a large excess of both diethylzinc and diiodo-methane is employed. Such excessive conditions are justified on account of the instability of the zinc carbenoid under the reaction conditions. To minimize the un-... 

The peak in /(Rh) located at 3-4 nm represents individual triblock copolymer chains. At 29 °C, an additional peak appears indicating the self-assembly of the triblock copolymer chains. Pentanediol (H0(CH2)50H) was added as the linking agent to couple each two functional ends of the triblock copolymer chains in the presence of pyridine. The resultant multiblock heteropolymer chains have a structure like (PMMA-/)-PS-/)-PMMA-c-)n, where c denotes the linking agent, pentanediol. The structure can also be written as (PMMA-Z>-PS)n, in which the PMMA block is twice longer than that in the initial triblock PMMA-Z>-PS-Z>-PMMA copolymer chain because each two PMMA blocks are connected together in the resultant multiblock copolymer. 

Preparation of Poly (propylene ether) Polyols. The polymerization of propylene oxide with zinc hexacyanocobaltate complexes in the presence of proton donors results in the production of low-molecular-weight polymers. Table V shows the variety of types of compounds that have been found to act this way. Since these compounds end up in the polymer chains, it seems reasonable to call them chain initiators. Thus, in essence, each of these compounds is activated by the catalyst to react with propylene oxide to form a hydroxylpropyl derivative. Thereafter, the reaction continues on the same basis, with the proton of the hydroxyl group reacting with further propylene oxide. This sequence is shown here with 1,5-pentanediol as the initiator. The hydroxyl... 

Figure 7. Time-conversion plot for 1,5-pentanediol initiated preparation of polypropylene ether) diol in pentane (propylene oxide/pentane wt ratio = 3) with Zns[Co(CN)6]2 glyme ...

The rate of formation of the low-molecular-weight polymer using 1,5-pentanediol as the initiator is shown in Figure 7. As in the preparation of the high-molecular-weight polymer, there was an initial slow reaction followed by a rapid one. Completion of the first part of the reaction was, in this case, characterized by disappearance of the initiator (21), as well as by dispersion of the catalyst. When this reaction was carried to complete consumption of monomer, addition of further monomer resulted in immediate resumption of the rapid rate. Once again, we see a similarity to a living polymerization. Both the rapid... 

In contrast to the results reported by Behr under biphasic conditions, the activity of the system increased considerably with the longer-chain alcohols, going from an initial turnover frequency of 7,200 h-1 for ethylene glycol to 321,000 h 1 for 1,2-butanediol. This remarkable increase in activity was attributed to the increased hydrophobicity and the resulting better solubility of the diol in 1,3-butadiene, where the ligand is preferentially found. In addition, the yield of di-telomers was remarkably lower than for ethylene glycol. The highest TOF recorded for diols under these conditions was 400,000 h-1 for 1,5-pentanediol [84],... 

Dioxathiocane 136 was synthesized from 1,5-pentanediol and thionyl chloride in 16% yield (Equation 23). This compound is prone to further cationic polymerization when TfOH, TfOMe, BF3NOEt2, TsOMe, and Mel were used as initiators <1998MAC1785>. 

Mixed y-Ga203-Al203 oxides of different stoichiometry were prepared by the solvothermal method from Ga(acac)3 and Al(OPr-i)3 as starting materials and were used as catalysts for selective reduction of NO with methane. The initial formation of gallium oxide nuclei controls the crystal structure of the mixed gallium-aluminum oxides. It is found that the acid density per surface area is independent of the Al Ga feed ratio but depends on the reaction medium (diethylenetriamine, 2-methylaminoethanol, toluene, 1,5-pentanediol etc.), whereby in diethylenetriamine the catalyst had lower densities of acid sites and showed a higher methane efficiency. 

Aside from the type III cyclizations described above, acetals have seen limited use in intermolecular Prins reactionsand extensive use as initiators for cation-alkene cyclizations.Only limited success has been achieved in Lewis acid catalyzed addition of acetals to alkenes. Better success has been achieved in the synthesis of C-glycosides by Lewis acid catalyzed addition of glycosyl acetates or glycals to alkenes. Johnson has extensively developed the use of acetals as initiators for cation-alkene cyclizations. Recent studies have shown that excellent asymmetric induction can be obtained using chiral acetals derived from optically active 2,3-butanediol or 2,4-pentanediol. - ... 

The j otochemical oxidation of 1,4-pentanediol (as a model cottpound) on illuminated suspensicais of Ti02 in oj enated acetonitrile media has been previously investigated by Fox et al. [ 4 ] the jAiotareacticxi produces a oenplex mixture of products, the cemposition of which evolves with extended illimination period. At short reaction times, the photooxidative transforma tion can be understood as involving initial oxidation of the alcoholic sites... 

Initially, cyclohexane is oxidized to the intermediate cyclohexyl hydroperoxide, CHHP. Then, the obtained CHHP is decomposed into the desired components cyclohexanone and cyclohexanol however, it is also partly decomposed into undesired by-products. A part of the formed cyclohexanol is further oxidized to cyclohexanone and a part of the formed cyclohexanone is converted to by-products. Part of the cyclohexane oxidation by-products are further destroyed (not shown in this figure). The by-products finally obtained include, in various amounts, acids such as adipic acid, e-hydroxycaproic acid, glutaric acid, succinic acid, valeric acid, caproic acid, propionic acid, acetic acid, formic acid, and noncondensable gases such as CO and CO2. In addition, several esters are formed between mainly cyclohexanol and the various carboxylic acids. The destinations of these by-products are quite diverse and depend on the producer for example, some of these byproducts are fed to combustion units for heat recovery purposes, while others are used as feedstock for chemicals such as 1,5-pentanediol, 1,6-hexanediol (HDO), and caprolactone. In general cyclohexanol is recovered from esters in a biphasic saponification step. 

The polymerization for polyaddition of a monomer that possesses an additional functionality allows the production of dual-function particles. The acyl chloride of the azo-initiator 4,4 -azo-4-cyanopentanoic add was reacted with 2,4-diethyl-l,5-pentanediol to yield a diol-functionahzed monomer, in addition to the azo-bond functional groups [118]. The functionahzed diol was first polymerized in a polyaddition reaction with a diisocyanate subsequently, it was possible to cleave the azo-bonds and to polymerize styrene in the nanodroplets. Such an approach combines free-radical polymerization and polyaddition, to produce hybrid block-copolymer particles. 

CHDM and 1,5-pentanediol. They observed that although the two codiols had similar reactivity, CHDA and IPA were consumed at different rates at the initial polycondensation stages. Nevertheless, the resulting terpolyesters were almost random, most probably due to the occurrence of extensive transesterification reactions taking place during polycondensation. 

Kinetic studies. The rate of formation of poly (propylene ether) diol using 1,5-pentanediol as an initiator and the zinc hexacyanocobaltate complex as a catalyst is shown in Figure 2. 

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