Compound 4-methoxybenzene

Kresge and Chiang15 showed that the dependence of rate coefficient upon the Hammett acidity function was not a safe criterion of mechanism and also explained how different dependencies of rate upon acidity function for different compounds could arise. Rate coefficients for detritiation of [3H]-2,4,6-tri-methoxybenzene followed the acidity function h0 in perchloric acid up to 3 M, i.e. k = 0.484 (Ao)1 07. so that a plot of log k versus —H0 would have a slope of 1.07, which implies the A-l mechanism. (New acidity function values479 would make this slope 1.14.) However, the diagnostic value of such a correlation was... 

Say you have to separate a mixture of benzoic acid (1), phenol (2), p-tolui-dine (4-Methylanaline) (3), and anisole (methoxybenzene) (4) by extraction. The numbers refer to the class of compound, as previously listed. We re assuming that none of the compounds react with any of the others and that you know we re using all four types as indicated. Phenol and 4-methylanaline are corrosive toxic poisons and if you get near these compounds in lab, be very careful. When they are used as an example on these pages, however, you are quite safe. Here s a sequence of tactics. 

The initiator formed from VCLt and A1(C2H5)2C1 is one of the most efficient means for syndioselective polymerization of propene, especially in the presence of a Lewis base such as anisole (methoxybenzene) [Doi, 1979a,b Natta et al., 1962 Zambelli et al., 1978, 1980], Other vanadium compounds such as vanadium acetylacetonate and various vanadates [VO(OR)xClp x), where x — 1,2,3] can be used in place of VCI4 but are more limited in their stereoselectivity [Doi et al., 1979]. Trialkylaluminum can also be used as a coinitiator, but only for VCI4. Syndiotacticity increases with decreasing temperature most of these syndioselective polymerizations are carried out below —40°C and usually at —78°C. The initiators must be prepared and used at low temperatures since most of them undergo decomposition at ambient and higher temperatures. There is considerable reduction of V(III) to V(II) with precipitation of ill-defined products that are low in activity and do not produce syndiotactic polymer, when the initiators are prepared at or warmed to temperatures above ambient. 

The genus Pimpinella (Apiaceae) produces rare phenylpropanoids with an unusual substitution pattern at the phenyl ring the (1 )-propenyl-2-hydroxy-5-methoxybenzene skeleton of these compounds... 

Menon presented a set of interesting liquid crystals 48 (Scheme 25) based on dibenzo[18]crown-6 modified with 2-hydroxy-3-methoxybenzene (48a), 3,4,5-trimethoxybenzene (48b), thiophene (48c), and pyrrole (48d) linked via a Schiff base [63]. All compounds are lacking long alkyl chains in the periphery. Nonetheless, broad mesophases with different geometries (SmC, SmA, N) were observed. 

Aromatic dibromides (1,2-dibromobenzene, 1,4-dibromobenzene, 1,2-dibromo-6-methoxybenzene, 2,7-dibromo-3,6-dimethoxynaphthalene, 5,10-dibromoanthracene) can be converted to lithioaryl bromides and subsequently to lithium bromoarenetellur-olates (Table 1 p. 155). An example of such a reaction sequence is given for 1,4-dibromobenzene3-4. With four moles of tert.-butyl lithium per mole of dibromoarene, the dilithio compounds that were formed were converted to the ditellurolates4 (Table 1 p. 155). 

Tellurium tetrachloride readily reacts with aromatic compounds that contain substituents promoting electrophilic attack. Thus, heating an excess of methoxybenzene and tellurium tetrachloride at 180° leads to the formation of bis[4-methoxyphenyl tellurium dichloride (Vol. IX, p. 1068). At lower temperatures, e.g., refluxing chloroform, only 4-methoxyphenyl tellurium trichloride is formed. This two-step reaction to diaryl tellurium dichlorides is promoted by elevated temperatures and the presence of an excess of the organic compound. 

Difunctional compounds will have 3 values larger than either of the mono-substituted compounds. For example, for benzaldehyde 3 = 0.23 and for methoxybenzene 3 = 0.15, but the 3 value for methoxybenzaldehyde will be larger than 0.23 by an increment which depends upon the difference between values (A 3) of the mono substituted compounds as follows ... 

Pichat et al. [119] previously reported an increase in the apparent first order rate constant with increasing hydrophobicity of a series of chlorophe-nols. In a follow up study of meta and para substituted methoxybenzenes no simple correlation was observed between the hydrophobicity (Kow) of the compound and the first order rate constant for the photocatalytic decomposition process [120]. They proposed this discrepancy was possibly due to an interaction between adsorbate molecules resulting from van der Waals forces. 

Plant phenolics represent a very large group of defensive compounds defined here as having a phenol (hydroxybenzene) moiety. In some instances substances having a phenolic precursor (e.g. methoxybenzene derivatives) have conveniently also been included in this category. Phenolics derive biosynthetically from hydroxycinnamoyl coenzyme A (yielding a phenyl-propanoid moiety). 

Hypervalent iodine compounds, such as l-(difluoroiodo)-4-methylbcnzcnc or l-(difluoroiodo)-4-methoxybenzene, can serve as oxidant and simultaneously as the source of fluoride ions. They are used for fluorodesulfurization reactions under mild conditions.229 230 The reagents arc crystalline and soluble in organic solvents. 

Arrange the following compounds in order of their reactivity towards nitration and give the formulae of the major products of the reactions (a) benzene, benzonitrile, methoxybenzene, tri-fluoromethyObenzene (b) acetanilide, benzoic acid, chlorobenzene, acetophenone (c) phenol, ethyl benzoate, nitrobenzene, bro-mobenzene. 

We have seen in Chapter 2 that electrophilic attack of methoxybenzene gives a mixture of the 2- and 4-isomers. The significance of the orthometallation process is the ease with which the 2-substituted compound can be obtained exclusively through reaction of the organolithi-um product with a variety of electrophiles (Scheme 10.4). 

NaBr/H20, LiBr on Amberlyst-15 resin, TiCU-LiCl, " SiCL, I2 with a Sml2 catalyst, and Lil on silica gel. Epoxides can be converted directly to 1,2-dichloro compounds by treatment with SOCI2 and pyridine, or with Ph3P and CCl4. These are two-step reactions a halohydrin is formed first and is then converted by the reagents to the dihalide (10-48). As expected, inversion is found at both carbons. Meso epoxides were cleaved enantioselectively with the chiral B-halodiisopinocampheylboranes (see 15-16), where the halogen was Cl, Br, or I. ° Diatomic iodine gives an iodohydrin with a 2,6-bis[2-(o-aminophenoxy) methyl]-4-bromo-l-methoxybenzene catalyst. ... 

Aryl tellurium trichlorides and tribromides condense with methoxybenzene 1,3-dihydroxybenzene, and dimethylaniline to give unsymmetrical diaryl tellurium dihalides. The condensations occur with the hydrogen atom in the para-position to the activating group in the aromatic compound. Aryl tellurium triiodides did not react . 

Orendt, A. M., R. Biefofsky, A. B. Pomilio, R. Contreras, and J. C. Facelli. 1991. Ab initio and NMR study of aromatic compounds with dicoordinate oxygenations Intramolecular hydrogen bonding in hydroxy- and methoxybenzene derivatives. J. Phys. Chem. 95 6179-6181. 

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