Phenols alkylphenols

Alkenes with between 4 and 24 carbon atoms react with phenol to produce an unrefined phenol—alkylphenol mixture. This mixture is fed to the distillation train where the phenol is removed for recycle and the product is isolated. The product is then stored in heated tanks made of stainless steel or phenoHc resin lined carbon steel. These tanks are blanketed with inert gas to avoid product discoloration associated with oxidation. 

Nonionic Polyoxyethylenated alkyl-phenols, alkylphenol ethoxylates Emulsifying agents Generally water-soluble Good chemical stability... 

At the end of World War II, Fischer-Tropsch technology was under study in most industrial nations. Coal can be gasified to produce synthesis gas (syngas), which can be converted to paraffinic liquid fuels and chemicals by the Fischer-Tropsch synthesis. Liquid product mainly contains benzene, toluene, xylene (BTX), phenols, alkylphenols and cresol. The low cost and high availability of crude oil, however, led to a decline in interest in liquid fuels made from coal. 

Several years ago, we were studying aromatic vinylation reactions using stoichiometric amounts of main element Lewis acids for example, phenols were o-vinylated with acetylene in the presence of SnCU and Bu3N. As an extension, we started to examine catalytic phenol alkylation, in which allenes were found to dimerize in the presence of palladium and phenol catalysts (Scheme 5). ° When 1,2-undecadiene was treated with Pd2(dba)3 (5 mol%), (p-io )3 (15 mol%), and p-nitrophenol (10 mol%) in refluxing THF for 12 h, (9 , 12 )-10-methyl-11-methylene-9,12-icosadiene was obtained in quantitative yield (Scheme 5). The added phenol played an important role, and no reaction took place in its absence. This reaction was effectively promoted by phenol having an electron-withdrawing group, p-nitrophenol however, the yield decreased when phenol, alkylphenol, or methoxyphenol was used. Because acetic acid also promoted the reaction, phenol was considered to function as Bronsted acid. 

Contamination of water by phenol or substituted phenols is very often due to industrial activity, because these are commercially very important chemicals. Phenol, cresylic acids, and cresols are used for making phenol-formaldehyde resins and tricesyl phosphates. Phenol, alkylphenol, and polyphenols are important raw materials for a wide variety of organic compounds, dyes, pharmaceuticals, plastizers, antioxidants, etc. Phenols are also present in effluents from coke ovens, blast furnaces, and shale oil processing [1]. 

There are many examples in the literature of the structural characterization of polymeric systems by FD-MS. Some of these will be briefly mentioned here. Saito and coworkers in Japan have studied a number of polymers by FD-MS. FD spectra were used to identify various poly(ethylene glycol) and poly(pro-pylene glycol) initiators (water, ethyleneimine, glycerol, sorbitol, sucrose). Structures of bisphenol A-based epoxy resins were elucidated. The degree of methylation in methylol melamine resins was assessed. Various novalak resins (made from phenol, alkylphenols, and epoxidized phenols) were characterized. Styrene polymerized with various initiators and chain transfer agents was studied in some cases deuterium labeling was used to help... 

Surfactants Organic material such as phenols alkylphenol (AP), aUcylphenolethoxylates (APEOs)... 

The third family (c. in Figure 9.1) less widespread, derived from the alkylphenols, offers as with the succinimides several possibilities of modification to the ratio of hydrophilic and lipophilic groups. Mannich s reaction of the alkyl-phenols also provides additives for lubricating oils. 

Detergents are metal salts of organic acids used primarily in crankcase lubricants. Alkylbenzenesulfonic acids, alkylphenols, sulfur- and methjiene-coupled alkyl phenols, carboxyUc acids, and alkylphosphonic acids are commonly used as their calcium, sodium, and magnesium salts. Calcium sulfonates, overbased with excess calcium hydroxide or calcium carbonate to neutralize acidic combustion and oxidation products, constitute 65% of the total detergent market. These are followed by calcium phenates at 31% (22). 

In 1993, worldwide phenol production was more than 5.2 million metric tons (1). The predominant uses of phenol are in phenoHc resins (qv), bisphenol A, caprolactam (qv), aniline, and alkylphenols (qv). 

Alkylphenols containing 3—12-carbon alkyl groups are produced from the corresponding alkenes under acid catalysis. Alkylphenols containing the methyl group were traditionally extracted from coal tar. Today they are produced by the alkylation of phenol with methanol. 

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). 

Of course, the physical properties of alkylphenols are comparable to phenol. The properties are strongly influenced by the type of alkyl substituent and its position on the ring. Alkylphenols, like phenol, are typically soflds at 25°C. Their form is affected by the size and configuration of the alkyl group, its position on the ring, and purity. They appear colorless, or white, to a pale yellow when pure (Table 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. 

The aromatic ring of alkylphenols imparts an acidic character to the hydroxyl group the piC of unhindered alkylphenols is 10—11 (2). Alkylphenols unsubstituted in the ortho position dissolve in aqueous caustic. As the carbon number of the alkyl chain increases, the solubihty of the alkah phenolate salt in water decreases, but aqueous caustic extractions of alkylphenols from an organic solution can be accomphshed at elevated temperatures. Bulky ortho substituents reduce the solubihty of the alkah phenolate in water. The term cryptophenol has been used to describe this phenomenon. A 35% solution of potassium hydroxide in methanol (Qaisen s alkah) dissolves such hindered phenols (3). 

There is a health benefit associated with hindering hydrogen bonding. Alkylphenols as a class are generally regarded as corrosive health hazards, but this corrosivity is eliminated when the hydroxyl group is flanked by bulky substituents in the ortho positions. In fact, hindered phenols as a class of compounds are utilized as antioxidants in plastics with FDA approval for indirect food contact. 

Alkylphenols can be synthesized by several approaches, including alkylation of a phenol, hydroxylation of an alkylbenzene, dehydrogenation of an alkylcyclohexanol, or ring closure of an appropriately substituted acycHc compound. The choice of approach depends on the target alkylphenol, availabihty of the starting materials, and cost of processing. The procedures discussed herein encompass commercial methods, general methods, and a few specific examples of commercial interest. 

All lation of Phenols. The approach used to synthesize commercially available alkylphenols is Friedel-Crafts alkylation. The specific procedure typically uses an alkene as the alkylating agent and an acid catalyst, generally a sulfonic acid. Alkene and catalyst interact to form a carbocation and counter ion (5) which interacts with phenol to form a 7T complex (6). This complex is held together by the overlap of the filled TT-orbital of the aromatic... 

The alkylation of phenol with an alkene using either acid or aluminum catalysis probably accounts for 95% of the commercially produced alkylphenols with alkyl groups of three carbons or larger. The alkenes are commercially available and environmentally kind. They do not produce by-products as do alkylations which use alcohols or alkyl haUdes. Together with an acid catalyst and the appropriate amount of phenol, mono-, di-, and trialkylphenols can be produced. 

Several methods are available to supplement the phenol alkylations described above. Primary alkylphenols can be produced using the more traditional Friedel-Crafts reaction. Thus an -butylphenol can be synthesized direcdy from a butyl haUde, phenol, and mild Lewis acid catalyst. Alternatively, butyryl chloride can be used to acylate phenol producing a butyrophenone. Reduction with hydrazine (a Wolff-Kishner reduction) generates butylphenol. 

Alkylphenols have been substituted for phenol as chain teaninatois in polycarbonates. In this role, PTBP (14) competes with the diol monomer for reactive chlorocarbonate sites. The ratio of butylphenol to diol controls the molecular weight of the polymer. 

Alkylphenols undergo a carboxylation reaction known as the Kolbe Schmidt reaction. In the following example, the phenolate anion of /)-nonylphenol (15) reacts with carbon dioxide under pressure. Neutralization generates a sahcyhc acid (16) (10). 

Reactions with Aldehydes and Ketones. An important use for alkylphenols is ia phenol—formaldehyde resias. These resias are classified as resoles or aovolaks (see Phenolic resins). Resoles are produced whea oae or more moles of formaldehyde react with oae mole of pheaol uader basic catalysis. These resias are thermosets. Novolaks are thermoplastic resias formed whea an excess of phenol reacts with formaldehyde under acidic conditions. The acid protonates formaldehyde to generate the alkylating electrophile (17). 

The versatility of this reaction is extended to a variety of aldehydes. The bisphenol derived from 2,6-di-/ f2 -butylphenol and furfural, (25) where R = furfuryl (13), is also used as an antioxidant. The utility of the 3,5-di-/ f2 -butyl-4-hydroxyben2yl moiety is evident in stabili2ets of all types (14), and its effectiveness has spurred investigations of derivatives of hindered alkylphenols to achieve better stahi1i2ing quaUties. Another example is the Michael addition of 2,6-di-/ f2 -butyl phenol to methyl acrylate. This reaction is carried out under basic conditions and yields methyl... 

Manufacture and Processing Alkylphenols of commercial importance are generally manufactured by the reaction of an alkene with phenol in the presence of an acid catalyst. The alkenes used vary from single species, such as isobutylene, to compHcated mixtures, such as propylene tetramer (dodecene). The alkene reacts with phenol to produce mono alkylphenols, dialkylphenols, and tri alkylphenols. The mono alkylphenols comprise 85% of all alkylphenol production. 

Among continuous reactors, the dominant system used to produce parasubstituted alkylphenols is a fixed-bed reactor holding a soHd acid catalyst. Figure 3 shows an example of this type of reactor. The phenol and alkene are premixed and heated or cooled to the desired feed temperature. This mix is fed to the reactor where it contacts the porous soHd, acid-impregnated catalyst. A key design consideration for this type of reactor is the removal of the heat of reaction. 

The most common approach to maintaining the desired reaction temperature is to operate with a significant excess of phenol in the reactor. An adiabatic reactor fed with 2 moles of phenol and 1 mole of isobutylene at 40°C would reach about 180°C if all the isobutylene formed PTBP. The selectivity towards the desired mono alkylphenol product almost always improves as the phenol to alkene mole ratio increases. These gains must be weighed... 

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