Hydroxyl 525 -amine hydroxylation theory

For imperfect epoxy-amine or polyoxypropylene-urethane networks (Mc=103-10 ), the front factor, A, in the rubber elasticity theories was always higher than the phantom value which may be due to a contribution by trapped entanglements. The crosslinking density of the networks was controlled by excess amine or hydroxyl groups, respectively, or by addition of monoepoxide. The reduced equilibrium moduli (equal to the concentration of elastically active network chains) of epoxy networks were the same in dry and swollen states and fitted equally well the theory with chemical contribution and A 1 or the phantom network value of A and a trapped entanglement contribution due to the similar shape of both contributions. For polyurethane networks from polyoxypro-pylene triol (M=2700), A 2 if only the chemical contribution was considered which could be explained by a trapped entanglement contribution. 

The Bronsted theory of acids and bases defines an acid as a proton donor and a base as a proton acceptor, i.e. a pro tic acid such as hydrochloric acid is a source of protons. Although the idea of an acidic hydrogen in organic compounds may initially be understood in terms of a carboxyl hydroxyl group, a hydrogen atom may become weakly acidic in a number of other circumstances, e.g. when it is attached to a carbon atom that is adjacent to a carbonyl group. On the other hand, a base such as an amine, or a carboxylate anion, is capable of accepting a proton. 

Early work from this group led to a theory according to which (a) the donor loses a hydrogen atom, (b) the radical so formed enters into a loose combination with a hydroxyl radical (from peroxidase-peroxide) and (c) the unchanged donor displaces a loosely bound hydroxyl radical. Loose combinations between such intermediate radicals are difficult to envisage, and a later hypothesis (372) is more acceptable. Aromatic amines, for example, lose an electron and proton to peroxidase-peroxide, the radical so formed being a hybrid of several canonical structures (structures A-C), which pair to give products appropriate to the particular amine (equation 32). When... 

The proton theory of acids and bases recognizes the existence of a large number and variety of bases, both molecular and ionic hydroxyl ion, amide ion, ethoxide ion, piperidine and other amines alcohols, ethers, acetate ion, hydrosulfide ion, cyanide ion, bisulfate ion, ketones, and many others. It also recognizes that acid-base phenomena do not depend upon the solvent. But its great weakness is that it ignores a large body of experimental data by restricting the use of the word acid to proton donors. For a time the only alternative to the proton theory seemed to be the theory of solvent systems. 

Hydrogen bonding. Interaction between molecules or portions of a molecule resulting from the Lewis acid or base properties of the molecular units. Most commonly applied to water or hydroxyl containing systems (e.g., alcohols) in the sense of Brpnsted-Lowry acid-base theory, but also found in molecules having hydrogen bound to nitrogen (amines and amides). 

---