Cresol chlorination

MCPA, l-methyl-A-chlorophenoxyacetic acid, Methoxone, CgH ClOj. Made by chlorination of o-cresol followed by reaction with chloroethanoic acid. While crystals, m.p. 118-119 C. As usually obtained, crude MCPA contains both 4- (60%) and 6- (40%) chloro-isomers, and is a light brown solid. Selective weedkiller. 

Methylphenol. y -Cresol is produced synthetically from toluene. Toluene is chlorinated and the resulting chlorotoluene is hydrolyzed to a mixture of methylphenols. Purification by distillation gives a mixture of 3-methylphenol and 4-methylphenol since they have nearly identical boiling points. Reaction of this mixture with isobutylene under acid catalysis forms 2,6-di-/ f2 -butyl-4-methylphenol and 2,4-di-/ f2 -butyl-5-methylphenol, which can then be separated by fractional distillation and debutylated to give the corresponding 3- and 4-methylphenols. A mixture of 3- and 4-methylphenols is also derived from petroleum cmde and coal tars. 

Methylene chloride is one of the more stable of the chlorinated hydrocarbon solvents. Its initial thermal degradation temperature is 120°C in dry air (1). This temperature decreases as the moisture content increases. The reaction produces mainly HCl with trace amounts of phosgene. Decomposition under these conditions can be inhibited by the addition of small quantities (0.0001—1.0%) of phenoHc compounds, eg, phenol, hydroquinone, -cresol, resorcinol, thymol, and 1-naphthol (2). Stabilization may also be effected by the addition of small amounts of amines (3) or a mixture of nitromethane and 1,4-dioxane. The latter diminishes attack on aluminum and inhibits kon-catalyzed reactions of methylene chloride (4). The addition of small amounts of epoxides can also inhibit aluminum reactions catalyzed by iron (5). On prolonged contact with water, methylene chloride hydrolyzes very slowly, forming HCl as the primary product. On prolonged heating with water in a sealed vessel at 140—170°C, methylene chloride yields formaldehyde and hydrochloric acid as shown by the following equation (6). 

The (9-cresol novolaks of commercial significance possess degrees of polymerization, n, of 1.7—4.4 and the epoxide functionaUty of the resultant glycidylated resins varies from 2.7 to 5.4. Softening points (Durran s) of the products are 35—99°C. The glycidylated phenol and o-cresol—novolak resins are soluble in ketones, 2-ethoxyethyl acetate, and toluene solvents. The commercial epoxy novolak products possess a residual hydrolyzable chlorine content of <0.15 wt% and a total chlorine content of ca 0.6 wt % (Table 2). 

Chlorinated phenolsf (other than those listed elsewhere includes trichlorophenols and chlorinated cresols)... 

Alkylphenols, ammonia, asbestos, chlorinated paraffins, 4-chloroaniline, cyanide, detergents, di- -butyl phthalate, polyaromatic hydrocarbons (PAHs e.g. anthracene, benzopyrene, methylcholanthrene, /i-naphthoflavone), nitrate, nitrite, petroleum oil, phenol, pentachlorophenol, 4-nitrophenol, dinitro-o-cresol, polychlorinated biphenyls (PCBs especially coplanar), polychlorinated dioxins, polybrominated naphthalenes, /i-sitosterol, sulfide, thiourea, urea, acid water, coal dust... 

Thus, reduction of the Mannich reaction product (65) from acetophenone leads to alcohol 66. Replacement of the hydroxyl group by chlorine (67) followed by displacement of halogen with the anion from o-cresol affords the ether 68. Removal of one of the methyl groups on nitrogen by means of the von Braun reaction or its modem equivalent (reaction with alkyl chloroformate followed by saponification) leads to racemic 69 which is then resolved with L-(+)-mandelic acid to give the levorotary antidepressant tomoxetine (69) [16]. 

Hypochlorous acid is a poorer chlorinating agent than chlorine itself so that C-chlorination does not generally take place, although hypochlorous acid can be removed with a more reactive aromatic substrate such as p-cresol. 

Kristiansen et al. [232] identified halogenated hydrocarbon byproducts in chlorinated seawater used for drinking water. Phenol, cresols, and catechols were present at low-ppb concentrations in San Diego Bay (CA, USA) [373]. 

As will be seen, the primary product from o-cresol cannot reconstitute the aromatic ring because of the CH3-group. Hence only NaCl is eliminated. The other two chlorine atoms are not hydrolytically removed and a quinol-like substance is formed, as the formula indicates ... 

Kanno et al. (1982) studied the aqueous reaction of 2-methylphenol (o-cresol) and other substituted aromatic hydrocarbons (toluidine, 1-naphthylamine, phenol, m- and p-cresol, pyro-catechol, resorcinol, hydroquinone, and 1-naphthol) with hypochlorous acid in the presence of ammonium ion. They reported that the aromatic ring was not chlorinated as expected but was cleaved by chloramine forming cyanogen chloride. The amount of cyanogen chloride formed was increased as the pH was lowered (Kanno et al, 1982). 

Hattula, M.L., Wasenius, V.-M., Reunanen. H., and Arstila, A.U. Acute toxicity of some chlorinated phenols, catechols and cresols in trout, Bull. Environ. Contam. Toxicol, 26(3) 295-298, 1981. 

The third method of dissolution is based on the mild chlorination of chemically modified wood according to Sakata and Morita (13) (Postchlorination method). Chlorination, in fact, resulted in enhanced solubility of chemically modified wood in solvents, including phenol. For example, chlorinated cyanoethylated wood does not only dissolve in cresol even at room temperature, but it also dissolves (under heating) in resorcinol, phenol and a LiCl-dimethylacetamide solution. 

Organic compounds, aromatic solvents (benzene, toluene, nitrobenzenes, and xylene), chlorinated aromatics (PCBs, chlorobenzenes, chloronaphthalene, endrin, and toxaphene), phenols and chlorophenols (cresol, resorcinol, and nitrophe-nols), polynuclear aromatics (acenaphthene, benzopyrenes, naphthalene, and biphenyl), pesticides and herbicides (DDT, aldrin, chlordane, BHCs, heptachlor, carbofuran, atrazine, simazine, alachlor, and aldicarb), chlorinated... 

Chlorinated Novolak Resins. Mixtures of a cresol formaldehyde Novolak resin and a photoactive compound cross-link at electron doses far smaller than the dose required for the Novolak resin alone (11). The reason for this accelerated cross-linking is the reactions between the ketene (an intermediate formed from the photoactive compound upon irradiation) and the Novolak resin. This reaction may be reduced by using a Novolak resin modified for this purpose, or by using certain additives. The rationale for developing a halogen-substituted Novolak resin is the control of the reaction between the intermediate ketene and the Novolak. 

Development of Resist Patterns. Development was done in AZ2401 developer diluted with 2 to 5 times its volume of water AZ2401 is an aqueous solution of KOH with a surfactant. When the resist films were exposed to electron beam doses of 5 iC/cm2 at 25 keV, it usually took 1.5 to 2.0 min for complete development of the images using a diazo-naphthoquinone sensitizer with o-chloro-cresol-formaldehyde Novolak resin in (1 3) AZ2401/water developer. With poly(2-methyl-l-pentene sulfone) the chlorinated Novolak resin exposed to I juC/cm2, it took 2.0 min in (1 4) AZ2401 developer for complete image development. 

The UV-absorption spectra of these Novolak resins vary widely depending upon substitution. However, the m-cresol-benzaldehyde Novolak resin is characteristic in its transparency within 300-320 nm in comparison with the cresol-formaldehyde resin. The chlorinated Novolak resin made of 2-chloro-5-methylphenol and formaldehyde has a slightly stronger UV absorption in this wavelength range, but weaker absorption in the range of 250 and 300 nm in comparison with a commercially available cresol-formaldehyde Novolak resin, as shown in Figure 4. 

All the flexible polyquinolines are readily soluble in chlorinated hydrocarbons such as methylene chloride and chloroform. Semirigid polyquinolines are soluble in tetrachloroethane or / /-cresol, but rigid polyquinolines are soluble only in strong acids like sulfuric and trifluoromethane sulfonic acid. Dilute solution properties of polyquinolines have been investigated by techniques such as membrane osmometry, light scattering, viscometry, and gel-permeation chromatography (96,97). 

This is prepared by the interaction of the foregoing oxide and an excess of bromine. It separates from alcohol as silvery prisms darkening and decomposing at 253° C. From its alkaline solution dilute acetic acid precipitates the amorphous oxide, which yields 5-chloro-3-bromo-o-cresol on treatment with chlorine water. 

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