2.5- Xylenol mixture

Xylenols (all six isomers) are now also in conunon use to form alkali-resistant grades of phenohc resins. High 3,5-xylenol mixtures are preferred. Also, resorcinol, which forms very reactive phenohc resins, is used in preparations of cold-setting adhesives. Higher homologs of phenol, like bisphenol A, are used to prepare special phenol-formaldehyde condensates. 

Triaryl phosphates are produced from the corresponding phenols (usually mixtures) by reaction with phosphoms oxychloride, usually in the presence of a catalyst (94—96). They are subsequently distilled and usually washed with aqueous bases to the desired level of purity. Tricresyl phosphate was originally made from petroleum-derived or coal-tar-derived cresyflc acids, ie, cresols, variously admixed with phenol and xylenols. Discovery of the toxicity of the ortho-cresyl isomers led manufacturers to select cresols having very Httle ortho-isomer. 

Dimethjlphenol (2,6-xylenol) is produced by the gas phase alkylation of phenol with methanol using modified alumina catalysis. The cmde product contains 2-methylphenol, 2,6-dimethylphenol, a minor amount of 2,4-dimethylphenol, and a mixture of trimethylphenols. The 2,6-dimethylphenol is purified by fractional distillation. The mixture of di- and trimethylphenols is sold as cresyHc acid for use as a solvent. 2,6-Dimethylphenol [576-26-1] is available in 55-gal dmms (208-L) and in bulk shipments in tank wagons and railcars. 

At other refineries, only two continuous stills in series are used, but these ate of 80—100 plate efficiency and yield pure grades of phenol and o-cresol and a base mixture of cresols, xylenols, and higher boiling tar acids. The latter are fractionated batchwise to various saleable grades of cresyHc acids. 

The cresols occur in cresylic acid, a mixture of the three cresols together with some xylenols and neutral oils, obtained from coal tar distillates. Only the /n-cresol has the three reactive positions necessary to give cross-linked resins and so this is normally the desired material. The o-isomer is easily removed by distillation but separation of the close-boiling m- and p-isomers is difficult and so mixtures of these two isomers are used in practice. 

Cresylic acid is a commercial mixture of phenolic compounds including phenol, cresols, and xylenols. This mixture varies widely according to its source. Properties of phenol, cresols, and xylenols are shown in Table 4-5 Cresylic acid constitutes part of the oxygen compounds found in crudes that are concentrated in the naphtha fraction obtained principally from naphthenic and asphaltic-based crudes. Phenolic compounds, which are weak acids, are extracted with relatively strong aqueous caustic solutions. 

By using the same molecular proportions the following m-nitrophenols were prepared in equally good yields from the corresponding m-nitroanilincs 3-methoxy-5-nitrophenol and 3-nitro-4,6-xylenol. In the former case it is advisable to use slightly more ice in the diazotization and add the diazonium solution to a mixture of equal volumes of sulfuric acid and water. 

Xylenol orange indicator. Finely grind (triturate) 0.20 g of the solid dyestuff with 50 g of potassium chloride (or nitrate). This solid mixture is used because solutions of xylenol orange are not very stable. 

The indicator solution is prepared by dissolving 0.5 g of xylenol orange in 100 mL of water. For storage it is best kept as a solid mixture with potassium nitrate (page 316). 

Pipette 25 mL of the bismuth solution (approx. 0.01 M) into a 500 mL conical flask and dilute with de-ionised water to about 150 mL. If necessary, adjust the pH to about 1 by the cautious addition of dilute aqueous ammonia or of dilute nitric acid use a pH meter. Add 30 mg of the xylenol orange/potassium nitrate mixture (see Section 10.50) and then titrate with standard 0.01 M EDTA solution until the red colour starts to fade. From this point add the titrant slowly until the end point is reached and the indicator changes to yellow. 

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. 

In the first step 2,6-xylenol is condensed with propylene oxide in the presence of NaOH at elevated temperature and pressure yielding I-(2,6-dimethyl)-phenoxy-propanoI-2 (DMFP). In the second step, ammonia is reacted with DMFP in the gas phase in the presence of hydrogen and a solid catalyst at a temperature of 450-475 K under atmospheric pressure. The product, l-(2,6-dimethyl)-phenoxy-2-aminopropane (DMFAP) is isolated from the condensed reaction mixture and purified as its hydrochloride. 

In a mixture to be fed to a continuous distillation column, the mole fraction of phenol is 0.35, o-cresol is 0.15, m-cresol is 0.30 and xylenols is 0.20. A product is required with a mole fraction of phenol of 0.952, o-cresol 0.0474 and m-cresol 0.0006. If the volatility to o-cresol of phenol is 1.26 and of m-cresol is 0.70, estimate how many theoretical plates would be required at total reflux. 

Determining the equilibrium relationships for a multicomponent mixture experimentally requires a considerable quantity of data, and one of two methods of simplification is usually adopted. For many systems, particularly those consisting of chemically similar substances, the relative volatilities of the components remain constant over a wide range of temperature and composition. This is illustrated in Table 11.2 for mixtures of phenol, ortho and meta-cresols, and xylenols, where the volatilities are shown relative to ortho-cresol. 

Raychoudhuri, A. and Gaikar, V.G. (1995) Adsorptive separations of 2,6-xylenol/cresol mixtures with zeolites. Sep. Technol, 5, 91. 

Since before World War II, multimillion pound quantities of cresols have been produced annually in the United States (O Brochta 1949), and domestic production and sales of cresols have steadily increased in recent years. Approximately 57.3 (USITC 1986), 73.3 (USITC 1988), and 82.3 (USITC 1989) million pounds of cresols were produced annually in the United States in 1986, 1987, and 1988, respectively. Respective sales were 56.6 (USITC 1986), 66.8 (USITC 1988), and 72.1 (USITC 1989) million pounds. These production totals include data on the manufacture of cresylic acid and exclude information on cresol production by coke and gas-retort ovens. The commercial mixture of cresol isomers, in which the m-isomer predominates and contains less than 5% phenol, is sometimes referred to as cresylic acid (Windholz et al. 1983). However, cresylic acids generally are composed of cresols, phenols, and xylenols they are defined as those mixtures in which over 50% will boil at temperatures above 204 C (Sax and Lewis 1987). In 1987, the national capacity for producing cresylics was 208 million pounds per year (CMR 1987). Information regarding the production levels of individual isomers and specific mixtures was unavailable. 

Chemically, wood tar is a complex mixture that contains at least 200 individual compounds, among which the following have been isolated (1) 2-methoxyphenol, 2-methoxy-4-ethylphenol, 5-methji-2-methoxyphenol, 2,6-xylenol, butyric acid, crotonic acid, l-hydroxy-2-propanone, butyrolactone, 2-methyl-3-hydroxy-4H-pyran-4-one, 2-methyl-2-propenal, methyl ethyl ketone, methyl isopropyl ketone, methyl furyl ketone, and 2-hydroxy-3-methyl-2-cyclopenten-l-one. 

Murexide Grind 10 mg of murexide with 5 g of reagent NaCl in a clean mortar use 0.2-0.4 g of the mixture for each titration, Xylenol orunge 0.5 g/100 mL H20 solution is stable indefinitely. 

All. three-necked flask is fitted with an efficient stirrer, a dropping funnel, and a gas inlet tube connected to a stream of purified nitrogen. A solution of 5 g of potassium hydroxide in 200 ml of water, 8 g (0.04 mole) of 4-bromo-2.6-xylenol and 200 ml of benzene is introduced. The stirrer is started and 1.3 g of potassium ferricyanide in 20 ml of water is added dropwise over a period of 30 minutes. After an additional 15 min of stirring, the mixture is transferred to a separatory funnel and the aqueous phase is drawn off the bottom. The yellow benzene solution is transferred to a 300 ml distilling flask and concentrated to 50 ml under water pump... 

TAR ACID. Any mixture of phenols present in tars or tar distillates and extractable by caustic soda solutions. Usually refers to tar acids from coal tar and includes phenol, cresols, and xylenols. When applie d to die products from other tars it should be qualified by the appropriate prefix, e.g., wood tar acid, lignite tar acid, etc. See also Coal Tar and Derivatives. 

Reaction of 4-methylsulphinyl-3,5-xylenol 1 in a 2 1 mixture of acetic anhydride-acetic acid at 100°C goes to completion within an hour and gives two products. The major product is 2-acetoxy-4-methylthio-3,5-xylenol 2 and the minor a crystalline solid A, (also) C11H14O3S. The... 

Binary mixtures of phenolic compounds (chlorophenol, phenol, cresol, xylenol) 182,183 Close-boiling-point problem... 

Because of the high antioxidant value of the p-cresol products, the work was extended to study the alkylation with a-olefins of three other readily available phenols phenol, 2,4-xylenol, and 2,6-xylenol. The nominal products were 2,4,6-tri(sec-alkyl)phenols, 6-(sec-alkyl)-2,4-xylends and 4-(sec-alkyl)-2,6-xylenols, as shown in the following reactions. Remember that these structural designations are for convenience the actual products are complex mixtures. Again, yields of the desired alkylated phenol were very high. The trialykylated phenol products were... 

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