Para-alkylphenol

Linear novolac resins prepared by reacting para-alkylphenols with paraformaldehyde are of interest for adhesive tackifiers. As expected for step-growth polymerization, the molecular weights and viscosities of such oligomers prepared in one exemplary study increased as the ratio of formaldehyde to para-nonylphenol was increased from 0.32 to 1.00.21 As is usually the case, however, these reactions were not carried out to full conversion, and the measured Mn of an oligomer prepared with an equimolar phenol-to-formaldehyde ratio was 1400 g/mol. Plots of apparent shear viscosity versus shear rate of these p-nonylphenol novolac resins showed non-Newtonian rheological behavior. 

Tabira Y, Nakai M, Asai D, Yakabe Y, Tahara Y, Shinmyozu T, Noguchi M, Takatsuki M, Shimohigashi Y (1999) Structural requirements of para-alkylphenols to bind to estrogen receptor. Eur J Biochem 262 240-245... 

Phenol reacts with hnear and branched alkenes in the presence of trill uoromethane-sulfonic acid (CF3SO3H) in chloroform to give the ortho- and para-aUcylphenols, in moderate yields (equation 8) °. With branched alkenes, the para-alkyl phenols are the major products. The regioselectivity is dramatically altered from entirely para-alkylphenol to ortlio-alkylphenol going from 100% potassium phenolate to 0% potassium phenolate in the presence of the Lewis acid AICI3. 

Vapor-phase alkylation of phenol with ferf-butyl alcohol in the presence of trivalent iron-substituted molecular sieve catalysts (FeMCM-41) gives para-fert-butylphenol with high regioselectivity . Supported heteropoly acid catalysts have been used in the heterogeneous alkylation reactions of 1-octene or nonene with phenol at 80-100°C. The catalyst H4SiWi204o/Si02 gives 90% para-alkylphenol and 10% orf/zo-alkylphenol. 

Alkylation of phenols using primary, secondary and tertiary alcohols was achieved using supercritical water (at the near-critical region, 250-350 °C). This process eliminates the need for environmentally hazardous organic solvents and acid catalysts. Both ortho-and para-alkylphenols were formed in these reactions, their ratio being dependent on the... 

Carbonized materials based on para-alkylphenols (50-53) had an unusually high degree of microporosity when compared with conventional phenol-formaldehyde resins. It was possible to generate high surface area materials from conventional phenol-formaldehyde resins by grinding the cured resin prior to carbonization. Carbonization of four phenol-formaldehyde powders containing a narrow particle size distribution showed that surface area increased rapidly as the resin particle size fell. The effect is extremely pronounced, and has not been previously reported. 

In an analogous fashion to catechols and hydroquinones, ortho- and para-alkylphenols undergo two-electron tt oxidation to form quinone-methides. Quinone-methides possess a significantly reduced propensity for redox chemistry than corresponding quinones and are therefore much more reactive... 

In addition, benzene is reacted with propylene to produce the important intermediate cumene, which is used to synthesize DCP, a commonly used peroxide curative for rubber. Cumene is also an intermediate in the manufacture of phenol, from which para-alkylphenol is made for production of rubber antioxidants and antiozo-nants. 

APE can be analyzed by capillary GC of derivatives (Table 7). The oligomer distribution is seen, along with fine stracture due to the small percentage of ort/ro-substituted phenol in the predominantly para-aLkylphenol from which the surfactant was made. 

For monosubstituted alkylphenols, the position of the alkyl radical relative to the hydroxyl function is designated either with a numerical locant or ortho, meta, or para. The alkyl side chain typically retains a trivial name. Thus 4-(l,l,3,3-tetramethylbutyl)phenol, 4-/ f2 octylphenol, and para-tert-octy Tph.eno (PTOP) all refer to stmcture (1). 

The solubihty of alkylphenols in water falls off precipitously as the number of carbons attached to the ring increases. They are generally soluble in common organic solvents acetone, alcohols, hydrocarbons, toluene. Solubihty in alcohols or heptane follows the generalization that "like dissolves like." The more polar the alkylphenol, the greater its solubihty in alcohols, but not in ahphatic hydrocarbons likewise with cresols and xylenols. The solubihty of an alkylphenol in a hydrocarbon solvent increases as the number of carbon atoms in the alkyl chain increases. High purity para substituted phenols, through Cg, can be obtained by crystallization from heptane. 

Nonylphenol ethoxylates (NPEOs) are extensively used as surfactants in industrial products (see Chap. 1). NPEOs are a mixture of polyethoxylated mono-alkylphenols, predominantly para-substituted, and are used in the manufacturing of paints, detergents, inks, and pesticides [435, 446]. Surfactants are common water pollutants because of their use in aqueous solutions, which are discharged into the environment in the form of wastewater from treatment plants or sludge stored in landfills. Degradation products of alkylphenol polyethoxylates, i. e., nonylphenol (NP), have the potential to be bioaccumulated, thereby becoming toxic to aquatic [447] and soil microorganisms [435,448]. 

However, our discussion will be restricted to oxidation of simple alkylated monohydric phenols (2-methoxy-4-alkylphenols), serving as models for noncondensed lignin units. In creosol (I) one ortho position and the para position is blocked, and coupling occurs at the 0-carbon atom under the conditions used. Other coupling mechanisms could not be detected (Figure 7). 

Fig. 1. Structures of the alkylphenols and related compounds discussed in this review. Technical nonylphenol consists of up to 22 isomers, most of them having a branched alkyl side-chain in the para position.

Titanium siliealites TS-1 and TS-2 catalyze hydroxylation in the aromatic ring of the monoalkylbenzenes studied to corresponding alkylphenols, using hydrogen peroxide as oxidant. Para-isomers are mainly formed in methanol or ethanol as solvents. In the case of ethyl- and 1-propylbenzenes, the first carbon atom of the aliphatic chain is also oxidised both to alcohols and ketones. As expected, the terminal methyl groups in all hydrocarbons are not oxidised. The probable reasons for this behaviour of titanium silicalites are discussed. 

Results in table 1 show, that a higher reaction temperature gives a greater selectivity to the p-substituted alkylphenol, thus increasing the rate of para-substitution as opposed to orthoalkylation and increases the 2,4-di-tert-butyl-phenol. The tested zeolite BETA has a pronoimced selectivity for the mono-alkylated para-substitution product as would be expected from its shape-selectivity. 

The oxidation of 4-alkylphenols 233 with [bis(acyloxy)iodo]arenes in the presence of pyridinium polyhydrogen fluoride, Py-(HF)j , as the source of fluoride anion results in nucleophilic i/tra-fluorination (Scheme 3.96) [302-304], This reaction has been used for the preparation of polycyclic 4-fluorocyclohexa-2,5-dienones 234 and 235 [302] and for the nucleophilic para-fluorination of tetrahydro-2-naphthol 236 [305],... 

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