3.5- Dimethylphenol, methylation with

In analogy to alkylation with chloroalkyl ethers, methyl ot-methoxyperfluoro-propionate reacts with 2,6-dimethylphenol to give the bispheiiol [7] (equation 7)... 

Figure 15.11 (a) Total ion clnomatogram of a Grob test mixture obtained on an Rtx-1701 column, and (b) re-injection of the entire clnomatogram on to an Rtx-5 column. Peak identification is as follows a, 2,3-butanediol b, decane c, undecane d, 1-octanol e, nonanal f, 2,6-dimethylphenol g, 2-ethylhexanoic acid h, 2,6-dimethylaniline i, decanoic acid methyl ester ], dicyclohexylamine k, undecanoic acid, methyl ester 1, dodecanoic acid, methyl ester. Adapted from Journal of High Resolution Chromatography, 21, M. J. Tomlinson and C. L. Wilkins, Evaluation of a semi-automated multidimensional gas chromatography-infrared-mass specti ometry system for initant analysis , pp. 347-354, 1998, with permission from Wiley-VCH. 

Methyl 2,7- and 3,6-dimethyl-l//-azepine-1-carboxylate also show marked differences towards acid hydrolysis. The 3,6-dimethyl isomer, with 10% sulfuric acid at 20°C, forms the expected A,-(ethoxycarbonyl)-2,5-dimethylaniline in high yield (82%) however, the 2,7-dimethyl isomer requires more forcing conditions to effect ring contraction and yields a mixture of A-(methoxycarbonyl)-2,6-dimethylaniline (16% mp 103-105°C), A-(methoxycarbonyl)-2,3-dimethylaniline (1% mp 90-92°C), 2,6-dimethylphenol (1%), and 3,4-dimethylphenol (6% mp 66-67 C).115 A mechanistic rationale for these results has been proposed. 

This reaction is similar to 13-1 and, like that one, generally requires activated substrates. With unactivated substrates, side reactions predominate, though aryl methyl ethers have been prepared from unactivated chlorides by treatment with MeO in HMPA. This reaction gives better yields than 13-1 and is used more often. A good solvent is liquid ammonia. The compound NaOMe reacted with o- and p-fluoronitrobenzenes 10 times faster in NH3 at — 70°C than in MeOH. Phase-transfer catalysis has also been used. The reaction of 4-iodotoluene and 3,4-dimethylphenol, in the presence of a copper catalyst and cesium carbonate, gave the diaryl ether (Ar—O—Ar ). Alcohols were coupled with aryl halides in the presence of palladium catalysts to give the Ar—O—R ether. Nickel catalysts have also been used. ... 

The literature on basic- and acid-catalyzed alkylation of phenol and of its derivatives is wide [1,2], since this class of reactions finds industrial application for the synthesis of several intermediates 2-methylphenol as a monomer for the synthesis of epoxy cresol novolac resin 2,5-dimethylphenol as an intermediate for the synthesis of antiseptics, dyes and antioxidants 2,6-dimethylphenol used for the manufacture of polyphenylenoxide resins, and 2,3,6-trimethylphenol as a starting material for the synthesis of vitamin E. The nature of the products obtained in phenol methylation is affected by the surface characteristics of the catalyst, since catalysts having acid features address the electrophilic substitution in the ortho and para positions with respect to the hydroxy group (steric effects in confined environments may however affect the ortho/para-C-alkylation ratio), while with basic catalysts the ortho positions become the... 

Fig. 14.8. Chromatogram and mass spectrum showing typical GC/MS data. The mass spectrum shown was obtained from the peak indicated with the arrow. Peak identification ldecane, 2 = 1-octanol, 3 = 2,6-dimethylphenol, 4 = 2-ethylhexanoic acid, 5 = 2,3-dimethylaniline, 6 = dodecane, 7 = decanoic acid, methyl ester, 8 = dicyclohexyl amine, 9 = undecanoic acid, methyl ester, 10-dodecanoic acid, methyl ester.

The reaction of o-xylene showed the formation of dimethylphenols in about 63% yield together with 21% of the dimer of 6,6-dimethyl-2,4-cyclohexadien-l-one, which involves ipso attack followed by a methyl shift and cycloadditive dimerization of the intermediate 6,6-dimethyl-2,4-cyclohexadien-l-one catalyzed by the acid (Scheme 5). 

Xylenol is an important starting material for insecticides, xylenol—formaldehyde resins, disinfectants, wood preservatives, and for synthesis of a-tocopherol (vitamin E) (258) and x//-CC-tocopherol acetate (USP 34-50/kg, October 1994). The Bayer insecticide Methiocarb is manufactured by reaction of 3,5-xylenol with methylsulfenyl chloride to yield 4-methylmercapto-3,5-xylenol, followed by reaction with methyl isocyanate (257). Disinfectants and preservatives are produced by chlorination to 4-chloro- and 2,4-dichloro-3,5-dimethylphenol (251). 

Poly(arylene oxide) copolymers were prepared by simultaneous and sequential oxidation of 1 1 mixtures of 2, 6-dimethylphenol (DMP), 2-methyl-6-phenylphenol (MPP), and 2,6-diphenylphenol (DPP), and methods were developed for determination of their structure. DMP and DPP yielded either random copolymers or block copolymers with crystallizable DMP and DPP blocks, depending on the order of oxidation and reaction conditions. Four types of copolymers were produced from MPP and DPP random copolymers, block copolymers with crystallizable DPP blocks, short block copolymers with DPP segments too short to permit crystallization, and mixed block copolymers containing DPP blocks and randomized MPP-DPP segments. Redistribution is so facile in the DMP-MPP system that only random copolymers were obtained, even on oxidation of a mixture of the two homopolymers. 

This reaction has been actively studied since it was first reported by Hay in 1959 (I), but most of the extensive literature, which includes several recent reviews (2-8), deals primarily with the complex polymerization mechanism. Few copolymers have been prepared by oxidative coupling of phenols, and only one copolymer system has been examined in any detail. Copolymers of 2,6-dimethylphenol (DMP) and 2,6-diphenylphenol (DPP) have been prepared and the effect of variations in polymerization procedure on the structure and properties of the copolymers examined (4, 9) this work has now been extended to copolymers of each of these monomers with a third phenol, 2-methyl-6-phenylphenol (MPP). This paper presents a study of the DMP-MPP and MPP-DPP copolymers and a comparison with the DMP-DPP system previously reported. 

Copolymers of 2,6-dimethylphenol with 2-methyl-6-ter -butylphenol, 2,6-diisopropylphenol, 2-methyl-6-phenylphenol, and 2,6-diphenylphenol have been reported (16) but only the 2,6-dimethylphenol (DMP)-2,6-diphenylphenol (DPP) pair, which is described in this report, has been examined in detail. This system is particularly attractive because high molecular weight homopolymers can be obtained under suitable conditions from both monomers, facilitating the analysis of the copolymers. Both random and block copolymers have been obtained by varying the polymerization conditions (1). 

Pd-catalyzed CO- bond forming reactions were performed by Buchwald [8] et al. with 2-dimethylamino-2 -di-(tert.-butyl)-biphenyl as ligand. 3,4-Dimethylphenol can be arylated smoothly with 2-chloro-4-methyl-toluene in the presence of sodium hydride [eq. (f)]. 

A key factor in the QA program is the performance control of the instrumentation. A number of test compounds have been recommended for checking the performance of a GC/MS instrument for the analysis of scheduled chemicals (34). These include DMMP, DMMP-rf9, trimethylphosphate, 2,6-dimethylphenol, 5-chloro-2-methylaniline, tri-n-butylphosphate, dibenzothiophene, malathion, and methyl stearate. DMMP is a moderately polar compound and is considered to be a good test compound for checking the GC performance. The deuterated form is recommended because it does not give cross-contamination in the analysis of authentic samples. However, because no scheduled chemicals can be brought on-site during an inspection, the use of DMMP-<79 has been replaced by trimethylphosphate for on-site analysis. The correctness of the intensity ratios in the El mass spectra can be verified by means of the test compounds with the different isotopic peaks 5-chloro-2-methylaniline... 

For the stabilization of various insoluble hydrocarbon polymers in carbon dioxide, it has been found that no one surfactant works well for all systems. Therefore it has become necessary to tailor the surfactants to the specific polymerization reaction. Through variation of not only the composition of the surfactants, but also their architectures, surfactants have been molecularly-engineered to be surface active—partitioning at the interface between the growing polymer particle and the CO2 continuous phase. The surfactants utilized to date include poly(FOA) homopolymer, poly(dimethylsiloxane) homopolymer with a polymerizable endgroup, poly(styrene-b-FOA), and poly(styrene-b-dimethylsiloxane). Through the utilization of these surfactants, the successful dispersion polymerization of methyl methacrylate (MMA), styrene, and 2,6-dimethylphenol in CO2 has been demonstrated. 

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