P-Cresol mixture

The once-mn tar acids are fractionated in three continuous-vacuum stills heated by superheated steam or circulating hot oil. These stills contain 40—50 bubble trays and operate at reflux ratios between 15 and 20 1. The overhead product from the first column is 90—95% phenol from the second, 90% (9-cresol and from the third, a 40 60 y -cresol—p-cresol mixture. Further fractionation gives the pure products. 

Polycondensates were prepared from pyrocatechol, o-cresol, p-cresol, mixtures of the latter with 2,4-dimethylphenol,2-tert-butyl-4-methylphenol, di-scc-butyl-phenol or other monoalkylphenols and their mixtures with dialkylphenols or alkoxyphenols. 

Mitsui Petrochemical Industries Limited and Sumitomo Chemical Co. Ltd., Japan have been operating two 20,000 tpa plants wherein they produce mixed cresols (60% m-cresol and 40% p-cresol mixture) for the last many years. However, they do not separate the mixture of meta- and para-cymenes but convert the cymenes mixture to meto-para-cresols. M/s. Yanshen Petrochemicals, China near Beijing have been operating a similar 20,000 tpa meto-para-cresols plant based on alkylation of toluene. Both the Japanese and Chinese plants have been producing pure meto-cresol and BHT. Through a recent agreement, Sumitomo Chemicals sell 10,000 tpa cresols mixture to Merisol and the remaining 10,000 tpa m-p-cresols are converted pure meto-cresol and BHT. From environmental point of view, cresol plants based on alkylation of toluene are much cleaner and more eco-friendly than those based on sulfonation of toluene. 

In Japan, Kobe Steel has sometime ago developed a high pressure crystallization technique known as Fine Cry Process in which m-, p-cresol mixture is introduced into a high pressure vessel of the piston-cylinder type and is crystallized adiabatically at 200 MPa. After draining off the mother liquor the system is decompressed and p-cresol emerges as the pure crystalline product [1]. 

The process is based on the fact that alkali metal-modified or alkaline earth modified zeolites of type X, A, L or ZMS-5 and also titanium dioxide, adsorb p-cresol more strongly than m-cresol. Thus m-/p-cresol mixtures can be separated in an adsorption column and can be dissolved again with a suitable desorbing liquid such as an aliphatic alcohol and ketone. The separating efficiency depends both on adsorption and desorption. 

When the lower-boiling o-cresol (boiling point 191.0 °C) has been distilled off, a m-/p-cresol mixture remains, with 70% m-content, which is difficult to separate by either crystallization or distillation (202.0 °C, and 201.9 °C resp.). 

If the separation of the isomers is carried out at the chlorotoluene stage (distilla-tion/crystallization), an o-/m-cresol mixture arises during hydrolysis of o-chloro-toluene in the ratio 1 1, from which pure m-cresol can be produced, whereas the hydrolysis of p-chlorotoluene gives a m-/p-cresol mixture. 

The optimum isomer distribution requires a low o-cymene content, since o-cymene is intricate to oxidize and inhibits the oxidation of the other cymenes. In practice, a mixture of 3% o-cymene, 64% m-cymene and 33% p-cymene is used. The oxidation of the cymene mixture is carried out to a peroxide content of around 20%, whereas the degree of oxidation of cumene in phenol synthesis is around 30%. In addition to cresols, the acid-cleaved reaction mixture contains acetone and unconverted cymene together with a wide range of co-products, such as isopropylbenzaldehyde, isopropylbenzyl alcohol, methyl acetophenone and isopropyltolyl alcohol. The m-/p-cresol mixture is over 99.5% pure the m-/p-ratio is 1.5 1. 

BHT can be produced by direct dialkylation of p-cresol with isobutene with sulfuric acid catalysis at 50 to 80 °C, or by monobutylation of m-/p-cresol mixtures. In the latter method, it is necessary to separate the monobutylated m-/p-mixture and further butylate the 2-tert-butyl-p-cresol to 2,6-di-tert-butyl-p-cresol. 

BHT consumption in Western Europe and the USA in 1985 was around 9,0001. Phosphate esters, which are used as additives for lubricants, are produced from m-/p-cresol mixtures. 

Production of pure cresols in the Western world in 1985 amounted to ca. 70,0001 o-cresol and 20,000 t p-cresol in addition, around 50,000 t of mixed cresols and 80,0001 m-/p-cresol mixtures were produced. 

Obtained by irradiation of a (Z)-(3-benzoylphenyl)azo tert-butyl sulfide and p-cresol mixture in the presence of potassium tert-butoxide in dimethyl sulfoxide for 3.5 h (53%) [1403]. 

The adaptation of the Bischler-Napieralski reaction to solid-phase synthesis has been described independently by two different groups. Meutermans reported the transformation of Merrifield resin-bound phenylalanine derivatives 32 to dihydroisoquinolines 33 in the presence of POCI3. The products 34 were liberated from the support using mixtures of HF/p-cresol. In contrast, Kunzer conducted solid-phase Bischler-Napieralski reactions on a 2-hydroxyethyl polystyrene support using the aromatic ring of the substrate 35 as a point of attachment to the resin. The cyclized products 36 were cleaved from the support by reaction with i-butylamine or n-pentylamine to afford 37. 

In some cases we may benefit from using an external agent to carry out the desired separation through crystallization. Thus, in the case of isomeric and non-isomeric mixtures of close-boiling acidic or basic materials we may use a suitable base or acid to carry out dissociative extractive crystallization, akin to dissociative extraction referred to in Section 4.2.1. For instance, for a mixture of p- and m-cresol or p-cresol and 2,6-xylenol we may use a base like anhydrous piperazine to obtain a precipitate of relatively pure p-cresol salt of piperazine, which can then be filtered and subjected to recovery of piperazine for recycle. Similarly, we may add a substance which forms an adduct with the desired substance. 

Applications Van der Maeden et al. [646] first used GE-HPLC for the qualitative and quantitative analysis of oligomeric mixtures, such as low-MW resins (epoxy up to 16-mer, o-cresol novolak up to 16-mer, p-cresol novolak up to 13-mer), prepolymers (poly-(2,6-diphenyl-p-phenylene oxide) up to 20-mer), PET (up to 14-mer) and ethoxylated octaphenol surfactants (up to 19-mer). In many GE-HPLC separations of oligomeric mixtures, a compromise has to be found between sample loading, injection volume and compatibility of the sample solvent and the initial phase system. Therefore,... 

A method suitable for quantification of the functional class of bis(ethanol)amine antistatics, which lack UV chromophores, consists of reaction with methyl orange [53]. Atmer 163 (alkyl-diethanol amine) has been determined as a yellow complex at 415 nm after interaction with a bromophenol/cresole mixture [64]. Hilton [65] coupled extracted phenolic antioxidants with diazotised p-nitroaniline in strongly acidic medium and carried out identification on the basis of the visible absorption spectrum in alkaline solution. The antioxidant Nonox Cl in... 

Linssen and de Vries [285] have examined 1 % di-f-butyl-p-cresol (DBPC) in low-MW poly(tetrahydro-furan) by means of DOSY (Figure 5.13). DOSY is a powerful tool for the analysis of polydisperse samples and complex mixtures, such as anionic surfactants. It is not to be expected that DOSY will rapidly become a standard tool in polymer/additive analysis. 

Radon forms a series of clathrate compounds (inclusion compounds) similar to those of argon, krypton, and xenon. These can be prepared by mixing trace amounts of radon with macro amounts of host substances and allowing the mixtures to crystallize. No chemical bonds are formed the radon is merely trapped in the lattice of surrounding atoms it therefore escapes when the host crystal melts or dissolves. Compounds prepared in this manner include radon hydrate, Rn 6H20 (Nikitin, 1936) radon-phenol clathrate, Rn 3C H 0H (Nikitin and Kovalskaya, 1952) radon-p-chlorophenol clathrate, Rn 3p-ClC H 0H (Nikitin and Ioffe, 1952) and radon-p-cresol clathrate, Rn bp-CH C H OH (Trofimov and Kazankin, 1966). Radon has also been reported to co-crystallize with sulfur dioxide, carbon dioxide, hydrogen chloride, and hydrogen sulfide (Nikitin, 1939). 

The FTIR spectra of the gas mixture evolved in thermal decomposition of Bisphenol AF poly(formal) (7) at various temperatures suggest the existence of benzene rings, C—O—C bonds, and C=C bonds. In a pyrogram of pyrolysis gas chromatography (Py-GC) of Bisphenol A (3), a-methylstyrene, phenol, p-cresol, 4-hydroxy-amethylstyrene, and isopropyl phenol are observed as major peak products. The cleavage reactions shown in Scheme (5) is suggested for the formation of phenol and 4-hydroxy-a-methylstyrene from Bisphenol A (3). 

While the cuprous cyanide solution is warmed gently (to 60°-70°) on the water bath, a solution of p-tolyldiazonium chloride is prepared as follows Heat 20 g. of p-toluidine with a mixture of 50 g. of concentrated hydrochloric acid and 150 c.c. of water until dissolution is complete. Immerse the solution in ice-water and stir vigorously with a glass rod so that the toluidine hydrochloride separates as far as possible in a microcrystalline form. Then cool the mixture in ice and diazotise with a solution of 16 g. of sodium nitrite in 80 c.c. of water, added until the nitrous acid test with potassium iodide-starch paper persists. The diazonium chloride solution so obtained is poured during the course of about ten minutes into the warm cuprous cyanide solution, which is meanwhile shaken frequently. After the diazo-solution has been added the reaction mixture is heated under an air condenser on the water bath fox a further quarter of an hour, and then the toluic nitrile is separated by distillation with steam (fume chamber, HCN ). The nitrile (which passes over as a yellowish oil) is extracted from the distillate with ether, the p-cresol produced as a by-product is removed by shaking the ethereal extract twice with 2 A-sodium hydroxide solution, the ether is evaporated,... 

A simulated moving bed system has been proposed for the production of p-cresol from mixtures of cresol isomers even derived from coal tar [52]. Neuzil et al. give details of the development of the adsorbent and desorbent system reviewing balancing mass transfer issues with selechvity [53]. The desorbent for the cresol system is 1-pentanol. For these Hquid adsorptive systems where highly polar molecules are adsorbed and desorbed with polar desorbents, the tolerance of the system for trace polar contaminants is higher because the feed and desorbent can more easily exchange with them on the surface of the zeolites. 

A method was proposed for the preparation of p-hydroxybenzoic acid by oxidation of p-cresol with atmospheric oxygen in an acetic acid-acetic anhydride mixture under catalysis of cobalt acetate, manganese(II) acetate, and sodium bromide (Litvintsev et al. 1994). This procedure ensures 60% yield of p-acetoxybenzoic acid and 100% conversion of the initial p-cresol. 

Cresol mixtures and the o- and p-isomers have been found to be weakly genotoxic in some in vitro assays inducing sister chromatid exchange and chromosomal aberrations in Chinese hamster ovary cells/ Results were negative with the meta-isomer, as were all in vivo assays. 

Three types of closely related cresols exist ortho-cresol (o-cresol), meta- cresol (m-cresol), and para-cresol (p-cresol). Pure cresols are colorless chemicals, but they may be found in brown mixtures such as creosote and cresylic acids (e.g., wood preservatives). Because these three types of cresols are manufactured separately and as mixtures, they can be found both separately and together. Cresols can be either solid or liquid, depending on how pure they are pure cresols are solid, while mixtures tend to be liquid. Cresols have a medicinal smell (odor) and when dissolved in water, they give it a medicinal smell and taste. Cresols do not evaporate quickly from water, but in rivers and lakes, they can be removed quickly by bacteria. Dissolved cresols can pass through soil into underground water sources. This may be a problem at hazardous waste sites where cresols are buried. Once cresols are in the water table, they may stay there for months without changing. Cresols in air quickly change and break down into smaller chemicals, some of which irritate the eyes. Cresols can also irritate the eyes. 

There are three isomers of cresol o-cresol, p-cresol, and m-cresol. These are described in detail in Chapter 3. In the following discussion, the effects of o-cresol and p-cresol, which have similar toxicities, are generally described prior to those of m-cresol, which is somewhat less toxic. Occasionally, data were available regarding the effects of cresol mixtures (containing the three isomers in varying proportions) and cresylic acids (technical mixtures containing other substances in addition to the three cresol isomers). These are generally discussed after the individual isomers. 

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