Phenolates, reactions

In most of their reactions phenols behave as nucleophiles and the reagents that act on them are electrophiles Either the hydroxyl oxygen or the aromatic ring may be the site of nucleophilic reactivity m a phenol Reactions that take place on the ring lead to elec trophilic aromatic substitution Table 24 4 summarizes the behavior of phenols m reac tions of this type... 

Hydroxythiophene also exists mainly in ketonic forms. Electrophilic reagents react either at oxygen or at C-5. O-Methyl and O-acetyl derivatives are obtained in alkaline solution, probably through intermediacy of the anion. In acidic solution, coupling with benzenediazonium ion, a characteristic phenolic reaction, is found to take place (Scheme 72). 

The alkalis and acids used to catalyze phenolic reactions are highly corrosive and any exposure is a potentially serious health threat. Those handling these materials should be thoroughly familiar with the appropriate Material Safety Data Sheets and emergency procedures. We do not purport to provide any specific health guidance here except to say that one should consult the appropriate references and be properly trained when making phenolic resins. 

There are two philosophies regarding how to best slow a runaway reaction. One view holds that simple water deluge is the best method as it provides immediate cooling and dilution. The anti position is that the batch should be deluged and neutralized simultaneously. Kumpinsky reports that minimum self-heat rates occur between pH 4 and 7 [78]. Since neutralization involves production of additional heat, because the pH of a runaway batch is rarely known, and since the phenolic reactions are catalyzed by acid, base, and salt it seems likely that simple deluge is the surest method. 

The key step in this sequence, achieved by exposure of 46 lo a mixture of sulfuric acid and acetic anhydride, involves opening of the cyclopropane ring by migration of a sigma bond from the quaternary center to one terminus of the former cyclo-l>ropane. This complex rearrangement, rather reminiscent of the i enone-phenol reaction, serves to both build the proper carbon. keleton and to provide ring C in the proper oxidation state. 

The portion absorheil by potash solution oo separition proved to k somewhat tesioous, and gave only a feeble phenol reaction with ferr ohioridc, A email poriloD of the oil was fractionated iu Order to git some idea of its possible uoiislicneDts. Tbe results were as follows — F.nuA k.o.n. 19]2). 5lf- cid Iiru 5r..t, 69 (1903), 1 1 -... 

Lim et al. also investigated HMTA-phenolic reactions with somewhat larger model compounds (e.g., two- and four-ring compounds) and established that similar reaction pathways to those described previously occurred.50 For these model compounds (as opposed to one-ring model compounds), which are more representative of typical oligomeric systems, increased molecular weight favored die formation of hydroxybenzylamines but not benzoxazines. This was suggested to be a steric effect. 

Epoxidized novolacs, 411 Epoxy -phenol networks, 411-416 properties of, 413-416 Epoxy-phenolic reaction kinetics of, 413 mechanism of, 411-412 Epoxy structures, 414 e-Caprolactam, 174... 

Hydroxymethyl-4,6-dimethylphenol, 406 Hydroxymethylphenol. See also Hydroxymethylated phenol reaction with melamine, 411 reaction with urea, 410 Hydroxymethyl substituents, condensation reactions of, 403... 

Phenol-epoxy reaction. See also Epoxy-phenolic reaction entries tertiary amine-catalyzed, 412 triphenylphosphine-catalyzed, 412 Phenol-formaldehyde novolac resin, preparation of, 429... 

The nmr analyses of the bottoms products given in Table IV show the material to have a large aliphatic content. The aromatic/aliphatic ratios of the fractions are higher than for the whole coal because of the presence of combined phenol reaction with Tetralin reduces these ratios considerably, presumably by transfer of much of this material to the solvent-range product, but some of it must remain in the bottoms as the aromatic/aliphatic ratio of the composite bottoms product from the fractions is higher than that from the whole coal. It was not possible to calculate the contribution that the diluents, excess solvent and combined phenol, made to the aromatic H, but the large monoaromatic content of the bottoms product must be due, in part, to these. 

The hydrocarbon-phenol reaction, catalysed by the etherate, was being run in petroleum ether solution in a sealed pressure bottle. The bottle burst, possibly owing to exothermic polymerisation of the diene. 

We emphasize that the above results have been observed only in the oxidation of sulfides and phenols, reactions known to follow radical mechanisms. A thorough investigation of the catalytic potential of the materials in other oxidation reactions (epoxidation, hydroxylations, etc.) is warranted. 

The quantitative nature of the silylamine-phenol reaction has been demonstrated for several different polymer systems (7). In our case, the charged PDMSX content was low to ensure that <1 phenolic group per novolac molecule reacted. This was done primarily to prevent extensive branching or crosslinking, and problems of insolubility and reproducibility associated with network formation... 

OH resonance shift of substituted phenol, 1n ppm, OH resonance shift of unsubstituted phenol, reaction constant, substituent constant,... 

Haloarene Alcohol/phenol Reaction conditions % yield... 

Diazonium salts can also be used to form ethers and phenols. Reaction of diazonium salt with an alcohol generates an ether, while thermal hydrolysis of the diazonium salt yields a phenol. Figure 13-30 illustrates both formations. As seen in Figure 13-31, this process also works on substituted aromatic systems. 

Es-Safi, N.E., Cheynier, V., and Moutounet, M., Implication of phenolic reactions in food organoleptic properties. J. Food Compost. Anal. 16, 535, 2003. 

Fulcrand, IT., Duenas, M., Salas, E., and Cheynier, V. (2006). Phenolic reactions during winemaking and aging. Am. J. Enol. Vitic. 57, 289-297. 

Heat resistant resin compositions based on BMI/aminophenol-Epoxy blends are achieved by reacting a BMI/p-aminophenol 1 1 adduct with epoxy resin (62). Both the secondary amine and phenol functionality may react with the epoxy resin and subsequently cure through an imidazole catalyst. Imidazole catalysts promote both the epoxy/phenol reaction and the anionic maleimide crosslinking. The formation of a 1 2 BMI/aminophenol adduct, as in Fig. 20, is claimed in a patent (63). The hydroxy terminated BMI/aminophenol adduct is an advantageous curing agent for epoxy resins when high temperature performance is desired. 

A polymer-bound guanidine base 31 has been used for the formation of aryl ethers from suitable phenols and alkyl halides. In addition to serving as a base to affect deprotonation, reagent 31 also acts as a sequestering agent for excess starting phenol (reaction 11).26... 

Li K Y, Kuo C H, Weeks J L (1979) A Kinetic Study of Ozone-Phenol Reaction in Aqueous Solution, American Institute of Chemical Engineers Journal 25 583-591. 

Lewis acids catalyze electrophilic reactions of carbonyl compounds with phenols. Reaction of ethyl pyruvate and 1-naphthol in the presence of a dibomacyclopentadienyl Zr(IV) complex affords the ortho-hy-dtoxyalkylated product in up to 87% ee (Scheme 121). Intervention of a Zr naphthoxide intermediate has been proposed, and addition of a small amount of water increases the enantioselectivity (293). 

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