Role of tacticity

Studies of the influence of structure on the photodegradation of poly(vinyl 

The stationary rate of carbonyl buildup decreases and the dehydrochlorination quantum yield increases as the content of isotactic triads increases [406, 407]. 

The quantum yield of dehydrochlorination under an inert atmosphere increases linearly with increasing isotatic content [403]. 

Hydrogen atoms in the syndiotactic diads of heterotactic sequences are more liable to radical attack than those in syndiotactic sequences [1747]. 

The initial concentration of radical (—CH2—CH—CH2—) depends on the overall isotactic content in poly(vinyl chloride) [1413]. 

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Many radical polymerization systems were examined hy Challa at a/. A number of papers were devoted to polymerization of methyl methacrylate, MM, in the presence of poly(methyl methacrylate). The role of tacticity of template was stressed. Isotactic PMM forms stereocomplex with syndiotactic PMM. Polymerizations of MM in the presence of isotactic PMM were carried out and the product (template + daughter polymer) was analyzed by NMR. When MM is polymerized in the polar solvent in the presence... 

Little work was conducted on the role of the solvent. The standard conditions for most of the subsequent work involved polymerizations in dichloromethane at - 60° to — 78°. However, a few experiments using sulfur dioxide as the solvent, with phosphorus pentafluoride as the catalyst, at —78°, gave, from GlcAnBzl3, a polymer of low d.p. having only a slightly lower specific rotation.92 Whether this was the result of slightly lower stereoregularity in the polymer, or contamination with a low-d.p. fraction of different tacticity, was not established. 

The submarine or surface launched strategic weapon is turbofan-powered, with a solid propint tandem rocket booster and nuclear warhead. Conversion to tactical role involves substitution of tactical guidance, a conventional HE warhead, and a turbojet cruise engine in place of the turbofan... 

A related approach exploited a A-cyanomethyl group to serve in the dual role of a nitrogen protecting group and a latent precursor of the formaldehyde im-inium ion (e.g., 478), and this innovative modification in tactics resulted in a simplified route to the c/.v-3a-aryloctahydroindole 474 (203a,c). To this end, the amino ketone 482 was readily prepared in one step by the reaction of 1,2-bis(trimethylsilyloxy)cyclopentene with A -benzyl-A -cyanomethyl amine. When 482 was exposed to [l-(3,4-methylenedioxyphenyl)ethenyl]lithium, a mixture (1 14) of 483 and 484 was obtained. It is noteworthy that the stereochemical sense... 

Is of serious concern. The role of chemical communication, in relation to proposed control tactics, of predators and bark beetles will be discussed. Emphasis will be on Thanaslmus dublus (F.) (Coleoptera Clerldae) and Medetera blstrlata Parent (Dlptera Dollchopodldae) which are primary predators of the southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera Scolytidae). 

There are 7 tactical considerations which define how effectively a protecting group will best fulfil its assigned strategic role of shielding a functional group from destruction (or reaction with another functional group) ... 

Figure 26.2 is a flowchart of appropriate, safe, effective, and efficient use of medications in the hospital setting (12). It incorporates the role of the prescriber, nurse, pharmacist, and patient in a typical inpatient environment. It also depicts the role of the organization s pharmacy and therapeutics committee and quality improvement functions, which will be discussed later in this chapter. The decision to treat a patient in a hospital or extended-care facility typically adds a nurse or other healthcare provider (respiratory therapist, etc.) to the trio described in the ambulatory care setting. Every time that individual has to read, interpret, decide, or act is yet another opportunity for a mistake to occur. Each of the steps in the medication use process provides an opportunity for correct or incorrect interpretation and implementation of the tactics that support the therapeutic plan. With this many opportunities for medication misadventures to occur, it is easy to understand why tracking and improving quality are important aspects of medication use. 

Of all the catalyst types, the sterically fluxional bis(2-arylindenyl) complexes749,752-768 produce elastomeric PP with the best combination of properties, that is, relatively high melting points and very low crystallinity, due to their stereoblock nature,769-772 but unfortunately their activity and molecular mass capability are too low at industrial polymerization temperatures (60-80 °C). The mechanism of stereoblock formation originally proposed by the inventors74 has recently been questioned and an active role of the counterion has been proposed to better account for the heptad distribution in the 13C NMR spectra of the elastomeric, stereoblock pp 773>773a These polymers are PP reactor blends, since they can be fractionated with solvents into low- and high-tacticity components.162,767,769,770,774,775... 

The Mn mediated radical additions offer an inherently flexible carbon carbon bond construction approach to amine synthesis. Because of the broad functional group compatibility in both the radical precursor and the aldehyde hydrazone acceptor, the roles of these precursors can be switched to result in the construction of either of two C C bonds at the chiral amine (Scheme 2.10) with excellent stereocontrol. The epimeric configuration can be selected by either (a) employing the enantiomeric auxiliary or (b) interchanging the roles of R and in the alkyl halide and aldehyde precursors [47]. By combining these two tactics, the optimal roles of R and with respect to yield and selectivity can be chosen. Such strategic flexibility contributes to the synthetic potential of these radical addition reactions. 

It is apparent that the conjunct roles of ester group and 8 "Backbone substituents are important in determination of the extent to which backbone segments experience mobility as the glass transition is approached. In this respect the influence of tacticity in 1,1-disubstituted alkyl methacrylate polymers requires investigation. 

Makarova NN, Godovsky YK, Kuzmin NN (1987) The role of polymer chain tacticity of cyclolinear polydecaorganocyclohexasiloxanes in the formation of a mesomorphic state. Makromol. Chemie, 188 119... 

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