Aldehyde resin solubility

Foundrez [Reichhold], TM for a group of water-soluble phenol-formaldehyde and urea-form-aldehyde resins for foundry applications. 

FIGURE A3.23 Solubility of a low-molecular-weight aldehyde resin (Laropal A 81 BASF). Data kindly provided by Dr Greg Smith and Classes of 2009, 2010 and 2011 of the Art Conservation Department at Buffalo State College. 

Brown resinous product formed. Aliphatic aldehydes (except formaldehyde) carbohydrates and soluble starch (sucrose and ordinary starch only faintly coloured). 

The lac resin is associated with two lac dyes, lac wax and an odiferous substance, and these materials may be present to a variable extent in shellac. The resin itself appears to be a polycondensate of aldehydic and hydroxy acids either as lactides or inter-esters. The resin constituents can be placed into two groups, an ether-soluble fraction (25% of the total) with an acid value of 100 and molecular weight of about 550, and an insoluble fraction with an acid value of 55 and a molecular weight of about 2000. 

Phenol (Cf HjOH) reacts readily with aldehydes to form oil. soluble compounds called phenolic resins that dry rapidly, are hard, chemical and abrasion resistant, but they tend to yellow with age. 

The reactions which take place when the mixed etch primer is applied to a metal are complex. Part of the phosphoric acid reacts with the zinc tetroxychromate pigment to form chromic acid, zinc phospliates and zinc chromates of lower basicity. The phosphoric acid also attacks the metal surface and forms on it a thin chromate-sealed phosphate film. Chromic acid is reduced by the alcohols in the presence of phosphoric acid to form chromium phosphate and aldehydes. It is believed that part of the chromium phosphate then reacts with the resin to form an insoluble complex. Excess zinc tetroxy chromate, and perhaps some more soluble less basic zinc chromes, remain to function as normal chromate pigments, i.e. to impart chromate to water penetrating the film during exposure. Although the primer film is hard... 

Aldol condensation of the zinc enolate of resin-bound alkyl ester 29 with aromatic aldehyde or ketone forms a P-hydroxy ester, which upon treatment with DIBAL-H leads to simultaneous reduction and cleavage of the ester moiety from the resin to give a soluble 1,3-diol 31 [31], Parallel synthesis utilizing three ester and nine carbonyl building blocks afforded a library of 27 analogs which was screened for antioxidative efficiency using a ferric thiocyanate assay. 

At a loading as low as 1 mol%, 10b promoted the hydrocyanation of A-allyl or -benzyl imines derived from aromatic and aliphatic aldehydes and of some ketones in very high yield and almost complete stereoselectivity (see Scheme 2). It is interesting to note that the soluble and the resin-bound catalysts performed equally well. Recovery and recycling of the supported catalyst was shown to occur without any erosion of chemical or stereochemical efficiency over ten reaction cycles. 

Scheme 15). Removal of the terminal xanthate moiety from polymer 66 was achieved using tributyltin hydride, after which the tin residues could be easily removed by precipitation of the polymer in methanol. The aldehyde group of the resulting polymer 67 was then reduced with sodium borohydride to give the soluble Wang resin analogue 68. 

The A -diphenylmethylene protection has also been used in the solid-phase mode for the synthesis of either unnatural amino acidst 1 or peptides (Scheme 67)J 1 Thereby, both Merrifield or Wang resins were used and the best base proved to be the organic soluble, nonionic phosphazene bases of Schwesinger, e.g. 2-tert-(butylimino)-2-(ethylamino)-l,3-di-methyl-l,3,2-diazaphosphinane (BEMP). As electrophiles alkyl halides,aldehydes, and Michael acceptors have been used. 

Benzyl Alcohol.—The simplest aromatic alcohol is the hydroxyl derivative of toluene and is known as benzyl alcohol, CeHs—CH2—OH. The radical, (CeHs—CH2—), is termed benzyl as in the alcohol and chloride above. The alcohol occurs as an ester in Peru balsam, in storax, a resin obtained from a plant sty rax, and in Tolu balsam from which the mother hydrocarbon toluene derives its name. On hydrolysis of the balsam benzyl alcohol is obtained. It is a liquid, b.p. 206.5°, slightly soluble in water and soluble in alcohol or ether. It may be prepared by those syntheses just given which yield primary alcohols. It may also be prepared by the reduction of the corresponding aldehyde, known as benzoic aldehyde or benzaldehyde (p. 655). On oxidation it yields the aldehyde and then an acid, benzoic acid. 

Polyitaconic add is converted completdy to the methyl ester with diazomethane (7), while Fisher esterification results in partial esterification of both itaconic acid homo- and copolymers (6). DMI homopolymers and its copolymer with butadiene can be reduced with lithium aluminum hydride to the polymeric alcohols, which on the basis of solubility, may under some conditions be partially cross-linked by intermolecular ester formation (6). Hydrazine converts polydimethyl itaccmate to the polymeric dihydrazide which is water-soluble and exhibits reducing properties. The hydrazide can be treated with aldehyde or ketones to form polymeric hydrazones (45). A cross-linked polymer of bi chloroethyl ita-conate) on treatment with trietlylamine, has been converted by partial quatemization to an anion exchange resin (46). 

The asymmetric aldol reaction was extended to different aldehydes and ketones in water (Scheme 3.13), catalysed by resin 41 and in the presence of a catalytic amount of the water-soluble DiMePEG (MW 2000) which facilitates the diffusion of reactants to resin. 

In searching for further expansions of dihydropyrimidine scaffold, Kappe and co-workers [359] immobilized 4-chloroacetoacetate on hydroxymethylpolystyrene resin by a microwave-assisted transesterification in 1,2-dichlorobenzene. The subsequent Biginelli condensation with the aldehyde and the urea components was performed in dioxane at 70 °C in the presence of catalytic amounts of HCl. Low yields, observed in the case of two out of twelve aldehyde building blocks employed, were attributed to the low solubility and reactivity of the bisureide side products. Further manipulations of the BigineUi products, involving thermal, amine-, or hydrazine-mediated cyclizations, gave access to various dihydropyrimidine-condensed heterocycles (461), (462), and (464) respectively (Scheme 95). 

Chemical characterization of DOM has been studied extensively, providing a wealth of information regarding its chemical properties [17,20,25,60,64-89]. CDOM is usually characterized as aquatic humic substances, such as humic and fulvic acids, owing to the presence of multiple double bonds in aromatic, aldehyde, and ketone groups. Isolation of humic substances involves their separation by adsorption on macroporous resins (e.g., XAD-8 or XAD-4) and elution at various pH [90]. Humic acids are soluble above a pH of 2, while fulvic acids are soluble at any pH. Solid phase extraction (SPE) onto Cig resin is also employed to isolate CDOM [44,73]. Amador and coworkers have shown that... 

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