1.4- Dimethoxybenzenes

It has been considered that nitric acid was responsible for the oxidation of the nitroso compoimd, but there is recent evidence from the catalysed nitration of p-dimethoxybenzene in carbon tetrachloride that dinitrogen tetroxide is involved ... 

With the oxides which are nitrated as the cations the difficulties are much less serious for the use of an acidity function is not involved. Comparison of 2,6-dimethoxy- and 3,5-dimethoxy-pyridine i-oxide with wt-dimethoxybenzene (which is nitrated at the encounter rate)... 

Halophenols without 2,6-disubstitution do not polymerize under oxidative displacement conditions. Oxidative side reactions at the ortho position may consume the initiator or intermpt the propagation step of the chain process. To prepare poly(phenylene oxide)s from unsubstituted 4-halophenols, it is necessary to employ the more drastic conditions of the Ullmaim ether synthesis. A cuprous chloride—pyridine complex in 1,4-dimethoxybenzene at 200°C converts the sodium salt of 4-bromophenol to poly(phenylene oxide) (1) ... 

Papaverine, used to treat heart diseases as a vasodilator, is a dmg that was originally made from vanillin but has since been made from veratrole and (9f2v (9-l,2-dimethoxybenzene. Vanillin is also used as a pharmaceutical excipient. 

The cyclic carbonate is easily cleaved by refluxing in water for 30 min. It can be converted to the 1,2-dimethoxybenzene derivative (aq. NaOH, Me2S04, reflux, 3 h). ... 

Dimethoxybenzene [150-78-7] M 137.2, m 57.2-57.8 . Steam distd. Crystd from hexane or benzene, and from MeOH or EtOH but these are wasteful due to high solubilities. Dried under vacuum. Also sublimes under vacuum. 

Eugenol methyl ether (4-allyl-l,2-dimethoxybenzene) [93-15-2] M 178.2, m -4 , b 127-129 /llmm, 146 /30mm, 154.7 /760mm, dj 1.0354, n 11.53411. Recrystd from hexane at low temp and redistd (preferably in vacuo). [Hillmer and Schoming Z Phys Chem [A] 167 407 1934 Briner and Fliszdr Helv Chim Acta 42 2063 1959.]... 

A solution consisting of 27.6 g. (0.2 mole) of p-dimethoxybenzene (Note 6), 4.0 g. of potassium hydroxide, and 400 ml. of methanol is placed in the apparatus. The beaker and contents are cooled with a 0° bath. The solution is electrolyzed with magnetic stirring for 6 hours at a current intensity maintained at 2.0 A (Notes 5, 7). The temperature of the solution varies between 8 and 14°. During this time small amounts of methanol are added from time to time to compensate for evaporation. 

The p-dimethoxybenzene was obtained from Aldrich Chemical Company, Inc. 

ArH = dimethoxybenzenes, anisol, xylenes, fluorene, diphenyl ether, etc R = alkyl, aryl... 

Table 12-2 gives some of Sterba s results for 1-naphthol, resorcinol, 1-methoxy-naphthalene, 3-methoxyphenol and 1,3-dimethoxybenzene. The data in the table show that the 1-naphthoxide ion is 108 times more reactive than the undissociated naphthol, which is 102 times more reactive than 1-methoxynaphthalene. The rate ratios for the monoanion of resorcinol relative to resorcinol, 3-methoxyphenol, and 1,3-dimethoxybenzene are of similar magnitudes. The dissociation of both OH groups of resorcinol gives rise to a rate constant (2.83 X 109 m -1 s-1) which, in our opinion, is probably mixing- or diffusion-controlled (see Sec. 12.9). 

Derbyshire and Waters202 carried out the first kinetic study, and showed that the chlorination of sodium toluene-m-sulphonate by hypochlorous acid at 21.5 °C was catalysed more strongly by sulphuric acid than by perchloric acid and that the rate was increased by addition of chloride ion. A more extensive examination by de la Mare et al.203 of the rate of chlorination of the more reactive compounds, anisole, phenol, and />-dimethoxybenzene by hypochlorous acid catalysed by perchloric acid, and with added silver perchlorate to suppress the formation of Cl2 and C120 (which would occur in the presence of Cl" and CIO-, respectively),... 

Br, 2,600 5-C1, 2,700 5-CN, 260277,277a. A good correlation of the substituted dimethoxybenzene data with the Hammett equation was obtained with p = —4.0 this value was taken to further confirm the heterolytic nature of the rate-determining step. The incursion of an apparently homolytic reaction was detected if the aromatics were distilled from diethyl ether, anomalously high but quite reasonably... 

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