Poly with nucleophiles, reactivities

To derive the maximum amount of information about intranuclear and intemuclear activation for nucleophilic substitution of bicyclo-aromatics, the kinetic studies on quinolines and isoquinolines are related herein to those on halo-1- and -2-nitro-naphthalenes, and data on polyazanaphthalenes are compared with those on poly-nitronaphthalenes. The reactivity rules thereby deduced are based on such limited data, however, that they should be regarded as tentative and subject to confirmation or modification on the basis of further experimental study. In many cases, only a single reaction has been investigated. From the data in Tables IX to XVI, one can derive certain conclusions about the effects of the nucleophile, leaving group, other substituents, solvent, and comparison temperature, all of which are summarized at the end of this section. 

Reactivity modes of the poly(pyrazolyl)borate alkylidyne complexes follow a number of recognised routes for transition metal complexes containing metal-carbon triple bonds, including ligand substitution or redox reactions at the transition metal centre, insertion of a molecule into the metal-carbon triple bond, and electrophilic or nucleophilic attack at the alkylidyne carbon, C. Cationic alkylidyne complexes generally react with nucleophiles at the alkylidyne carbon, whereas neutral alkylidyne complexes can react at either the metal centre or the alkylidyne carbon. Substantive work has been devoted to neutral and cationic alkylidyne complexes bearing heteroatom substituents. Differences between the chemistry of the various Tp complexes have previously been rationalised largely on the basis of steric effects. 

To obtain poly(silamine) having a phenylene linkage in each repeating unit, the anionic polyaddition reactions between l,4-bis(vinyldimethylsilyl)benzene (VSB) and DAO and/or PIP were carried out. Because the nucleophilic reactivity of VSB was almost the same as that of DVS, 4) the polyaddition proceeded smoothly in a homogeneous solution. From the GPC analysis of the polymer obtained by the reaction between VSB and DAO, the Mn of the obtained polymer was 1,600 with a distribution factor (Mw / Mn) of 2.33. The molecular weight distribution (MWD) was close to the value from Flory s theory of polyaddition reactions. (79) After the polymer was washed three times with DMF, the Mn of the polymer became 4,300 due to exclusion of the low MW fractions. 

The fundamental theory of phase transfer catalysis (PTC) has been reviewed extensively. Rather than attempt to find a mutual solvent for all of the reactive species, an appropriate catalyst is identified which modifies the solubility characteristics of one of the reactive species relative to the phase in which it is poorly solubilized. The literature on the use of PTC in the preparation of nitriles, halides, ether, and dihalocarbenes is extensive. Although PTC in the synthesis of C- and 0-alkylated organic compounds has been studied, the use of PTC in polymer synthesis or polymer modification is not as well studied. A general review of PTC in polymer synthesis was published by Mathias. FrecheE described the use of PTC in the modification of halogenated polymers such as poly(vinyl bromide), and Nishikubo and co-workers disclosed the reaction of poly(chloromethylstyrene) with nucleophiles under PTC conditions. Liotta and co-workers reported the 0-alkylation of bituminous coal with either 1-bromoheptane or 1-bromooctadecane. Poor 0-alkylation efficiencies were reported with alkali metal hydroxides but excellent reactivity and efficiencies were found with the use of quaternary ammonium hydroxides, especially tetrabutyl- and tetrahexylammonium hydroxides. These results are indeed noteworthy because coal is a mineral and is not thought of as a reactive and swellable polymer. Clearly if coal can be efficiently 0-alkylated under PTC conditions, then efficient 0-alkylation of cellulose ethers should also be possible. 

These polymers can be prepared by several teclmiques, but the route utilized most in this work is summarized in Scheme I. It is based on the use of a reactive macromolecular intermediate - poly(dichlorophosphazene) (3), which can be produced either by the ring-opening polymerization of compound 2 or by the living cationic polymerization of 4. Replacement of the chlorine atoms in 3 by organic side units is accomplished by treatment of 3 with nucleophiles, such as the sodium salts of alcolK>ls or phenols or with primary or secondary amines. Two or more different side groups can be introduced into the same macromolecule by simultaneous or sequential exposure to the two nucleophiles. 

Preparation of poly(dichlorophosphazene), (NPCl2)n> a polymeric intermediate from which the great majority of POPs have been prepared by nucleophilic substitution of the highly reactive chlorine atoms with carefully selected organic substituents... 

The nucleophilic substitution on poly(vinyl chloroformate) with phenol under phase transfer catalysis conditions has been studied. The 13c-NMR spectra of partly modified polymers have been examined in detail in the region of the tertiary carbon atoms of the main chain. The results have shown that the substitution reaction proceeds without degradation of the polymer and selectively with the chloroformate functions belonging to the different triads, isotactic sequences being the most reactive ones. 

Such configurational as well as conformational effects have been also reported by MILLAN et al. in the case of nucleophilic substitution of poly(vinyl chloride) with sodium thiophenate (14) and with sodium isooctylthioglycolate or isooctylthiosalicylate (15). The authors have shown that these reactions proceed selectively on the isotactic TT diads which can only exist either in the GTTG isotactic or in the TTTG heterotactic triads, the former ones being much more reactive than the latter ones. 

In order to determine the efficiency of the polymers as reagents in nucleophilic catalysis, it was decided to study the rate of quaternization with benzyl chloride. Table I shows the second-order-rate constants for the benzylation reaction in ethanol. Comparison with DMAP indicates that poly(butadiene-co-pyrrolidinopyridine) is the most reactive of all the polymers examined and is even more reactive than the monomeric model. This enhanced reactivity is probably due to the enhanced hydrophobicity of the polymer chain in the vicinity of the reactive sites. 

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