Bases alcoholic hydroxyl attachment

The resihency and dyeabihty of poly(vinyl alcohol) fibers is improved by a process incorporating -hydroxybenzaldehyde to provide a site for the formation of a stable Mannich base. Hydroxyl groups on the fiber are converted to acetal groups by -hydroxybenzaldehyde. Subsequent reaction with formaldehyde and ammonia or an alkylamine is rapid and forms a stable Mannich base that is attached to the polymer backbone (94). 

A glance at the pKa values in Table 3.1 reveals that many classes of compounds can act either as acids or as bases, depending on the reaction environment. Such materials are termed amphoteric. They must have an acidic proton (i.e., a proton attached to an electronegative element or group) and unshared pairs of electrons that can be donated to a proton. For example, water, alcohols, and other hydroxylic compounds as well as amines and amides are all amphoteric materials. Comparing the p.Ka s of these materials permits an assessment of the predominant behavior in a given environment. For example, if an amine is dissolved in water, it could function as an acid or a base. To determine which behavior will predominate, the position of the equilibrium can be determined for each process. Comparison of these values will indicate which will be the principal behavior. Thus, as an acid, the amine would donate a proton to water to give an amide anion and the hydronium ion. 

When the reactivity difference between the two hydroxyl functions is not sufficient to attach selectively the tosyl group on one of the alcohol substituents, recourse to triisopropylphenyl sulfonylchloride generally provides a useful solution [ 136]. This strategy has been employed in numerous cases. For example, selective monotosylation of diol 218 followed by base-catalyzed cycHzation gave the useful glyceraldehyde building block 219 [137] (Scheme 56). 

As with alkyl halides, alcohols are classified into three groups primary (1°), secondary (2°), and tertiary (3°) alcohols. This class cation is based on the degree of substitution ofthe carbon to which the hydroxyl group is directly attached. If the carbon has only one other carbon attached to it, the carbon is said to be a primary carbon and the alcohol is a primary alcohol ... 

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