Methylol derivatives Formation

Thiourea will react with neutralised formalin at 20-30°C to form methylol derivatives which are slowly deposited from solution. Heating of methylol thiourea aqueous solutions at about 60°C will cause the formation of resins, the reaction being accelerated by acidic conditions. As the resin average molecular weight increases with further reaction the resin becomes hydrophobic and separates from the aqueous phase on cooling. Further reaction leads to separation at reaction temperatures, in contrast to urea-formaldehyde resins, which can form homogeneous transparent gels in aqueous dispersion. 

Both the Henry reaction and the reverse demethylolation are synthetically useful in the chemistry of polynitroaliphatic compounds. The Henry reaction is commonly used to mask the natural chemistry of an aliphatic nitro or terminal em-dinitro group by removing the acidic a -proton(s). In Section 1.7 we discussed the conversion of Q ,ty-dinitroalkanes to their bis-methylol derivatives before subjecting them to oxidative nitration and subsequent demethylolation with base, a procedure which results in the formation of Q ,Q , y, y-tetranitroalkanes. ... 

Methylol Formation. Polyacrylamide reacts with formaldehyde to form an N-methylol derivative. The reaction is conducted at pH 7-8.8 to avoid cross-linking, which will occur at lower pH. The copolymer can also be prepared by copolymerizing acrylamide with commercially available N-methylolacrylamide [924-42-5], C4HyN02. These derivatives are useful in several mining apphcations (49,50). They are also useful as chemical grouts. 

Base-catalyzed formation of mono-methylol derivates OH O-... 

These are a member of the phenolics. In the presence of acid catalysts, and with the mole ratio of formaldehyde to phenol less than 1, the methylol derivatives condense with phenol to form, first, dihydroxydiphenyl methane and, on further eondensation with the methyl bridge formation, fusible and soluble linear low polymers called novolacs are formed, having the following structure ... 

Even at the early stages of absorption of formaldehyde, no methylol derivatives could be detected in these resins. This is apparently due to the rapid formation of methylene bonds in the resins. In polyamide 68, methylol derivatives were detected (up to 3% of the weight of the polymer 15 min after the beginning of the experiment) at all stages of the absorption of formaldehyde. The content of methylol groups was determined polar igraphically. It corresponded to the amount of free polyformaldehyde liberated in the decomposition of methylol groups in alkaline medium [27]. However, even at the maximum absorption of formaldehyde, polyamide 68 remains entirely soluble in tricresol imder these conditions. 

Thus methylene and ether links arise through competitive reactions. Ether formation will be favoured when there are few free o- and p- positions available for attack by carbonium ions. Thus when these active positions are blocked by non-reactive substituents or if complete methylolation has occurred (as in trimethylolphenol) then ether formation is to be expected. This is in accordance with the finding that treatment of the methylol derivative of p-t-butyl-o-cresol with dilute hydrochloric acid yields the corresponding dibenzyl ether [9] ... 

The utility of alkalies as catalysts fox the formation of methylol derivatives by reaction of formaldehy de with compounds containing active hydrogen atoms has been emphasized (page 109). 

Effect of Catalyst. From a beha iorist ie standpoint, reaction catalysts may be classified according to tchether they are alkaline or acidic in nature.. Although different acids and bases may i ry somewhat in their action, such variations are usually subordinate. Hydrogen and hydroxyl ions may thus be regarded as the principal factors in reaction catalysis. As i dth other ionnaldehyde reactions, alkalies tend to favor the formation of methylol derivatives and acids tend to favor the formation of methylene derivatives. 

XTnder acid conditions, the situation is reversed in that the conversion of methylol derivatives to methylene derivatives is usually more rapid than their formation. Granger suggests that this is because mono-methylol derivatives are converted to methylene derivatives as soon as they are formed.. s a result, the introduction of more than one methylol group in the simple phenol is prevented and the polynuclear phenols thus obtained, as would be expected, react less readily with additional formaldehyde. 

Phenol Alcohols. As has been previously pointed out, the simplest defimte reaction products of formaldehyde with phenols are the methylol-phenols or phenol alcohols. Although some of these derivath es are too reactive to be isolated, a number have been obtained as pure crystalline products. In some respects they are analogous to the methylol derivatives of aldehydes and ketones, a similarity which is readily demonstrated when the keto- or ortho- and para-quinoidal forms of the phenolic nucleus are designated in the structural formula. The mechanism of their formation from the primary phenolic hemifoniLals may involve tautomeric rearrangements of the sort indicated below ... 

The second phase in resole formation is reaction of the activated phenol with the aldehyde to form the phenol alcohol derivative. When the aldehyde is formaldehyde, the derivative is a hydroxymethyl phenol and the process is known as methylolation. Scheme 2 illustrates this reaction. Since resoles are usually made with excess aldehyde, more than one substitution may be made on the ring. When the reactants are phenol and formaldehyde, up to three methylol groups may be substituted. This reaction has been extensively studied and the rates of... 

Resole syntheses entail substitution of formaldehyde (or formaldehyde derivatives) on phenolic ortho and para positions followed by methylol condensation reactions which form dimers and oligomers. Under basic conditions, pheno-late rings are the reactive species for electrophilic aromatic substitution reactions. A simplified mechanism is generally used to depict the formaldehyde substitution on the phenol rings (Fig. 7.21). It should be noted that this mechanism does not account for pH effects, the type of catalyst, or the formation of hemiformals. Mixtures of mono-, di-, and trihydroxymethyl-substituted phenols are produced. 

Fig. 9.26. Mechanism of the formation of a urea/formalde-hyde resin from methylol urea (R1 = H in formula A possible preparation Figure 9.25) or dimethylol urea (R1 = HO—CH2 in formula A possible preparation Figure 9.25). The substituents R1, R2, and R3 represent the growing —CH2—NH— C(=0)—NH—CH2— chains as well as the derivatives thereof that are twice methylenated on N atoms.

The chemical shifts of the carbons in the saligenin-derived portion of these compounds are not much different from those in saligenin itself, except for the methylene carbon of the methylol group (C-7 ). The chemical shift of this carbon is shifted down field as expected on formation of an ether linkage. 

Di(metbylol -amine N, N -Bis( -hydroxy-, metbylyamine, or Di(methanol)-amine, HN(CH20H)2 mw 77.08y N 18.17% may be considered as the parent corapd of its nitrated deriv, although not used to prep it Di(methylol)-nitromine Dinitrote or Nitro-imino-dimethanol Dinitrate,. (0 N)N(CH20N02)2 mw 212.08, N 16.41% a precursor product obtd during formation of l,5-endomethylene-3,7-dinitro-l,3,5,7-tetrazacyclooctane on neutralization with NH.jOH of the filtrate from the prepn of RDX by the method of Hale (CA 20, 40) ... 

The reactions of the alkenylphenols resulting in the syntheses referred to have been studied v h respect to the derivation of methylol compounds and the formation of unsaturated ethers. 

Reduction of isoanacardic aldehyde gave a methylol which could also be synthesised directly from cardanol together with formation of some of the 4,6-bis-methylol. The monomethylol compound isoanacardic alcohol was an effective solvent extractant for the borate anion (ref. 279, 293). The isomeric compound, anacardic alcohol (ref. 88) was similarly obtained from anacardic acid (ref. 180). This In conjunction with the teriary amine Aliquat 336 was highly effective for the solvent extraction of the borate anion (ref. 293). Both these substances were comparable in properties to the 2,6-bis(hydroxymethyl) derivatives of 4-t nonylphenol and to 4-t octyl-2-chloro-6-hydroxymethylphenol (ref. 294). 

The reaction of phenol and formaldehyde in alkaline conditions results in the formation of o- and p-methylol phenols. These are more reactive towards formaldehyde than the original phenol and undergo rapid substitution with the formation of di- and trimethylol derivatives. The methylol phenols obtained are relatively stable in an alkaline medium but can undergo self-condensation to form dinuclear and polynuclear phenols (of low molecular weight) in which the phenolic nuclei are bridged by methylene groups. Thus in the base-catalyzed condensation of phenol and formaldehyde, there is a tendency for polynuclear phenols, as well as mono-, di-, and trimethylol phenols to be formed. 

Many cellulose derivatives form lyotropic liquid crystals in suitable solvents and several thermotropic cellulose derivatives have been reported (1-3) Cellulosic liquid crystalline systems reported prior to early 1982 have been tabulated (1). Since then, some new substituted cellulosic derivatives which form thermotropic cholesteric phases have been prepared (4), and much effort has been devoted to investigating the previously-reported systems. Anisotropic solutions of cellulose acetate and triacetate in tri-fluoroacetic acid have attracted the attention of several groups. Chiroptical properties (5,6), refractive index (7), phase boundaries (8), nuclear magnetic resonance spectra (9,10) and differential scanning calorimetry (11,12) have been reported for this system. However, trifluoroacetic acid causes degradation of cellulosic polymers this calls into question some of the physical measurements on these mesophases, because time is required for the mesophase solutions to achieve their equilibrium order. Mixtures of trifluoroacetic acid with chlorinated solvents have been employed to minimize this problem (13), and anisotropic solutions of cellulose acetate and triacetate in other solvents have been examined (14,15). The mesophase formed by (hydroxypropyl)cellulose (HPC) in water (16) is stable and easy to handle, and has thus attracted further attention (10,11,17-19), as has the thermotropic mesophase of HPC (20). Detailed studies of mesophase formation and chain rigidity for HPC in dimethyl acetamide (21) and for the benzoic acid ester of HPC in acetone and benzene (22) have been published. Anisotropic solutions of methylol cellulose in dimethyl sulfoxide (23) and of cellulose in dimethyl acetamide/ LiCl (24) were reported. Cellulose tricarbanilate in methyl ethyl ketone forms a liquid crystalline solution (25) with optical properties which are quite distinct from those of previously reported cholesteric cellulosic mesophases (26). 

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