Phenol condensation with formaldehyde

It is reported that an industrial explosion was initiated by charging potassium hydroxide in place of potassium carbonate to the chloro-nitro compound in the sulfoxide [1], Dry potassium carbonate is a useful base for nucleophilic displacement of chlorine in such systems, reaction being controlled by addition of the nucleophile. The carbonate is not soluble in DMSO and possesses no significant nucleophilic activity itself. Hydroxides have, to create phenoxide salts as the first product. These are better nucleophiles than their progenitor, and also base-destabilised nitro compounds. Result heat and probable loss of control. As it nears its boiling point DMSO also becomes susceptible to exothermic breakdown, initially to methanethiol and formaldehyde. Methanethiolate is an even better nucleophile than a phenoxide and also a fairly proficient reducer of nitro-groups, while formaldehyde condenses with phenols under base catalysis in a reaction which has itself caused many an industrial runaway and explosion. There is thus a choice of routes to disaster. Industrial scale nucleophilic substitution on chloro-nitroaromatics has previously demonstrated considerable hazard in presence of water or hydroxide, even in solvents not themselves prone to exothermic decomposition [2],... 

A real co-condensation between phenol and urea can be performed by two ways (I) reaction of methylol phenols with urea [98-101] (2) acidic reaction of UFC (urea-formaldehyde concentrate) with phenol followed by an alkaline reaction [102,103]. 

Baekeland found that a relatively stable resole prepolymer could be obtained by the controlled condensation of phenol and formaldehyde under alkaline conditions. These linear polymers of phenol-formaldehyde (PF) may be converted to infusible cross-linked polymers called resites by heating or by the addition of mineral acids. As shown in structure 4.80, the initial products obtained when formaldehyde is condensed with phenol are hydroxybenzyl alcohols. The linear resole polymer is called an A-stage resin, and the cross-linked resite is called a C-stage resin. 

The reaction is of importance, especially when as in (ii.) it is used for the production of phenolic methanols. Formaldehyde, when condensed with phenols in presence of acid or basic catalysts, yields resinous substances, which, when dehydrated under pressure, yield hard resinojds (Bakelite, Novolak). (See J. S. C. I. (C. I.), 1937,103). 

A procedure based on condensation with phenol and paraform (used as formaldehyde source) was developed to convert spent UNEX solvent (CCD, PEG-400, Ph2-CMPO, and FS-13) into a solid infusible resin for disposal. The resulting material is insoluble in aqueous alkali and acidic solutions and organic solvents. Incorporation of FS-13 in the cross-linked polymer was confirmed by physicochemical methods. Resistance of the cured resin to high temperatures was proven by thermogravimetry... 

If polymeric procyanidins extractable from conifer tree barks are to be used in adhesive formulations requiring condensation with phenol-formaldehyde prepolymers, these reactions must be performed at acidic pH conditions, and because of solubility limitations, this will probably require the use of sulfonate derivatives. 

Lignin can be modified by condensation with phenol, formaldehyde, amino acids [3731, or diazonium salts 1387,3881. 

Use Organic synthesis (condenses with phenol and formaldehyde, copolymerizes with maleic anhydride), solvent, dye, and pharmaceutical manufacture. 

Today formaldehyde finds widespread use in the hardening of gelatin, preservation of food, disinfection, tanning of leather and, most important, in the production of resins by condensation with phenol (bakelite) and in the synthetic organic chemical industry. 

It was reported that the reaction of starch with phenol in the presence of a Lewis acid such as AICI3 resulted in resins of controlled melt viscosity.252 Probably, the product results from the hydrolysis of starch to glucose with conbversion of the latter into 5-(hydroxymethyl)-2-furaldehyde, which subsequently condensed with phenol.253 The reaction of starch with phenol without any catalyst required temperatures between 200 and 260 °C, and the resultant resinous product was then hardened by condensation with formaldehyde.254 Mastication of either glycerol or phenol with starch and water was said not to involve alcoholysis, but instead results in the formation of polymeric products.255 Reactions with gossypol256,257 and propylene glycol258 that were performed in the presence of a basic catalyst were in fact polymerization reactions and not alcoholyses. 

Figure 3. Formaldehyde conversion (7), dihydroxydiphenylmethane yield (a) and selectivity (o) upon condensation with phenol for 4V6 h at 180 C, vs. phenol/formaldehyde-molar ratio. Catalyst SAPO-5.

Figure 4. Formaldehyde conversion upon condensation with phenol for 4V4 h at 180 C, vs. reaction time. ALPO-5-P (o) and SAPO-5 (a) were used as catalysts. Phenol/formalde-hyde molar ratio 2/1.

Table 1. Formaldehyde conversion and dihydroxydiphenylmethane selectivities upon condensation with phenol, for 4Vfe h at 180 C (phenol/formaldehyde molar ratio 2/1).

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 ... 

Epoxy phenolic adhesives are polyepoxy compounds which possess epoxy reactivity and phenolic resin heat resistance. These are prepared by condensing epichlorohydrin and novolac phenolics (phenol/formaldehyde ratio > 1). A recent Japanese patent issued to Mitsubishi Petrochemical Co. describes the preparation of epoxy resins from epichlorohydrin condensation with phenolic resins prepared from phenol and substituted aldehydes, e.g., vanillin. These resins (23) have high epoxy contents (epoxy equivalent weights >200) and relatively high softening points (85-95°C). 

Another important class of polymeric surfactants that are used for demulsifica-tion is those based on alkoxylated alkyl phenol formaldehyde condensates, with... 

Formaldehyde polymerizes by condensation with phenol and urea to form phenol— and urea— formaldehyde resins which are popular and inexpensive adhesives. They are paint and coatings often used in coatings when combined with alkyds, epoxides, polyesters, or acrylic to give strong flexible films. 

The structure of the aldehyde used for condensation with phenolic compounds can vary from formaldehyde to others [73] as shown below ... 

These aldehydes react on acid condensation with phenols to give novolac-type products. Base-catalyzed condensation is not practical with acetaldehyde since it undergoes rapid aldol condensation and self-resinification reactions. Acid condensations involving acetaldehyde or its trimer paraldehyde and phenol give soluble and permanently fusible resins, comparable to the novolacs. Aldehyde with no a hydrogens react in a manner similar to formaldehyde ... 

Phenolic resins were among the first synthetic resins explored by the coating industry, initially used to modify properties of oil-based varnishes as a replacement for some natural hard resins. They are essentially solvent-soluble phenol-formaldehyde condensates with reactive methyllol groups. They are widely used as cross-linkers for thermosetting baking finishes, yielding films with excellent solvent and corrosion resistance properties coupled with favorable mechanical properties. 

Formaldehyde reacts with phenol by electrophilic substitution at the 2-, 4- and 6-positions of phenol and will subsequently condense, forming a densely cross-linked network. This reaction can be catalyzed by acid as well as base catalysts. The nature of the product obtained is largely dependent on the type of phenol, the molar ratio of formaldehyde to phenol (f p) and the catalyst used. Phenolic resins are mainly divided into two broad classes resoles and novolacs. 

Obtained by hydrolysis of 8-isobutyryl-5-methoxy-methyleneoxy-2,2-dim-ethylchroman-7-ol (SM) in the presence of 2,4,6-trihydroxy-3-methyl-acetophenone. The hydrolysis of SM proceeds with the liberation of formaldehyde which condenses with phenol under these acidic conditions [5716]. 

Condensation is stopped by adjusting pH to 5-8. The prepolymer is stable for several months (>38 °C). Further condensation with additional furfuryl alcohol or with aldehydes (furfural or formaldehyde) and with phenol or urea is again activated by strong acids. 

Phenohc resins are produced by the condensation of phenol or a substituted phenol, such as cresol, with formaldehyde. These low cost resins have been produced commercially for more than 100 years and in the 1990s are produced by more than 40 companies in the United States. They are employed as adhesives in the plywood industry and in numerous under-the-hood appHcations in the automotive industry. Because of the cycHc nature of the automotive and home building industry, the consumption of phenol for the production of phenohc resins is subject to cycHc swings greater than that of the economy as a whole. 

Resoles. The advancement and cure of resole resins foUow reaction steps similar to those used for resin preparation the pH is 9 or higher and reaction temperature should not exceed 180°C. Methylol groups condense with other methylols to give dibenzyl ethers and react at the ortho and para positions on the phenol to give diphenyknethylenes. In addition, dibenzyl ethers eliminate formaldehyde to give diphenyknethanes. 

Methyl violet [8004-87-3] Cl Basic Violet 1 (17), is made by the air oxidation of dimethyl aniline in the presence of salt, phenol, and a copper sulfate catalyst. Initially, some of the dimethyl aniline is oxidized to formaldehyde and /V-methyl aniline under those conditions. The formaldehyde then reacts with dimethyl aniline to produce N,N,]S7,1S7-tetramethyldiaminodiphenylmethane, which is oxidized to Michler s hydrol [119-58-4]. The hydrol condenses with... 

Di- and Triisobutylcncs. Diisobutylene [18923-87-0] and tnisobutylenes are prepared by heating the sulfuric acid extract of isobutylene from a separation process to about 90°C. A 90% yield containing 80% dimers and 20% trimers results. Use centers on the dimer, CgH, a mixture of 2,4,4-trimethylpentene-1 and -2. Most of the dimer-trimer mixture is added to the gasoline pool as an octane improver. The balance is used for alkylation of phenols to yield octylphenol, which in turn is ethoxylated or condensed with formaldehyde. The water-soluble ethoxylated phenols are used as surface-active agents in textiles, paints, caulks, and sealants (see Alkylphenols). 

ButylatedPhenols and Cresols. Butylated phenols and cresols, used primarily as oxidation inhibitors and chain terrninators, are manufactured by direct alkylation of the phenol using a wide variety of conditions and acid catalysts, including sulfuric acid, -toluenesulfonic acid, and sulfonic acid ion-exchange resins (110,111). By use of a small amount of catalyst and short residence times, the first-formed, ortho-alkylated products can be made to predominate. Eor the preparation of the 2,6-substituted products, aluminum phenoxides generated in situ from the phenol being alkylated are used as catalyst. Reaction conditions are controlled to minimise formation of the thermodynamically favored 4-substituted products (see Alkylphenols). The most commonly used is -/ fZ-butylphenol [98-54-4] for manufacture of phenoHc resins. The tert-huty group leaves only two rather than three active sites for condensation with formaldehyde and thus modifies the characteristics of the resin. 

The epoxy cresol—novolak resins (2) are prepared by glycidylation of o-cresol—formaldehyde condensates in the same manner as the phenol—novolak resins. The o-cresol—formaldehyde condensates are prepared under acidic conditions with formaldehyde—o-cresol ratios of less than unity. 

Reaction rates are at a minimum at pH 3, and, unlike with the phenol-formaldehyde condensates, which have a minimum at pH 7, setting can occur under neutral conditions. 

In commercial practice resorcinol is seldom used on its own but in conjunction with phenol when condensing with formaldehyde. Such a material is Aerodux 185, introduced by Aero Research Ltd (now part of Ciba-Geigy) in 1944. 

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