Alcohol mixtures, stabilized electrons

Some typical dispersion polymerization recipes and the electron micrograph of the uniform polymeric particles with Recipe I are given in Table 5 and Fig. 10, respectively. As seen in Table 5, the alcohols or alcohol-water mixtures are usually utilized as the dispersion media for the dispersion polymerization of apolar monomers. In order to achieve the monodispersity in the final product, a costabilizer can be used together with a primary steric stabilizer, which is usually in the polymeric form as in... 

Carbonium ions can be generated at a variety of oxidation levels. The alkyl carbocation can be generated from alkyl halides by reaction with a Lewis acid (RCl + AICI3) or by protonation of alcohols or alkenes. The reaction of an alkyl halide and aluminium trichloride with an aromatic ring is known as the Friedel-Crafts alkylation. The order of stability of a carbocation is tertiary > secondary > primary. Since many alkylation processes are slower than rearrangements, a secondary or tertiary carbocation may be formed before aromatic substitution occurs. Alkylation of benzene with 1-chloropropane in the presence of aluminium trichloride at 35 °C for 5 hours gave a 2 3 mixture of n- and isopropylbenzene (Scheme 4.5). Since the alkylbenzenes such as toluene and the xylenes (dimethylbenzenes) are more electron rich than benzene itself, it is difficult to prevent polysubsiitution and consequently mixtures of polyalkylated benzenes may be obtained. On the other hand, nitro compounds are sufficiently deactivated for the reaction to be unsuccessful. 

As an alternative to the manner in which the stability of the intermediate species 277 is raised by increasing electron input to phosphorus, a reduction in nucleophilic character of the original carbonyl oxygen might be contemplated. In this respect, it may be noted that a reaction between the lithium salt of diisopropyl (fluoromethyl)phosphonate and the ketones R R CO affords both the alkene (s) predicted from the Wittig mechanism, but also the alcohols (Pr 0)2p(0)CHFC(0H)R R as mixtures of diastereoisomers, distinguishable spectroscopically but not separable ... 

Attack at C2 is more sterically hindered due to the eminaZ-dimethyl group, so 75 may be formed in greater amormt. This observation is difficult to predict without experimental data, so in the oxymercuration ofunsymmetrical alkenes, anticipate a mixture of both possible alcohols. In other words, assume that oxymercuration of unsymmetrical internal alkenes will give a 1 1 mixture of two alcohols unless there is a compelling reason for one to predominate, such as electronic stabilization, severe steric hindrance, or resonance effects. Exceptions to this assumption will rarely be encountered in this book. 

In many cases, mixtures of the 3- and 5-fluoroalkyl regioisomers were obtained. However, when reactions were performed in neutral alcoholic media, 5-fluoroalkyl-5-hydroxypyrazoline intermediates 94 were isolated instead of the dehydrated final products 96 (entries 1, 6,7, 9 Table 1) [48]. This observation conld be explained on the basis of the influence of the fluoroalkyl group adjacent to the hydroxyl gronp that stabilizes the hydroxypyrazoline 94, preventing the dehydration process (via a). In addition, the dehydration involves a cationic intermediate, whose formation could explain why, when R is an electron-withdrawing group, the dehydration does not occur or occurs with difficulty. In contrast, in an acidic medium, 94 was not observed, probably because the dehydration follows a different mechanism (via b). In acidic EtOH solution (H2SO4 catalyst), at room temperature or at reflux, the... 

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