Substituents benzene

Line No. Benzene substituents Nucleophile Solvent Rate constant (temp. °C) 106 jc liter mole-1 see-i Energy of activation keal mole-1 Frequency factor logioA Ref. 

Consuming hydrogen is mainly a function of the number of benzene substituents. Dealkylation of polysubstituted benzene increases hydrogen consumption and gas production (methane). For example, dealkylating one mole xylene mixture produces two methane moles and one mole of benzene it consumes two moles of hydrogen. 

These alkaloids bear close resemblance to peepuloidine (140), the main alkaloid of Piper peepuloides Roxb., a medicinal plant from India. The main structural problem with 140 was the location of the five benzenic substituents,... 

Previous work has shown that the electronic characteristics of the benzene substituent in triarylphosphine chlororhodium complexes have a marked influence on the rate of olefin hydrogenation catalyzed by these compounds. Thus, in the hydrogenation of cyclohexene using L3RhCl the rate decreased as L = tri-p-methoxyphenylphosphine > triphenylphosphine > tri-p-fluorophenylphosphine (14). In the hydrogenation of 1-hexene with catalysts prepared by treating dicyclooctene rhodium chloride with 2.2-2.5 equivalents of substituted triarylphosphines, the substituent effect on the rate was p-methoxy > p-methyl >> p-chloro (15). No mention could be found of any product stereochemistry studies using this type of catalyst. 

Figs. 3-4. The failure of the Hammett cj-constants for the correlation of log (kjk-g) for (3) the nitration of monosubstituted benzenes—substituents with large resonance interactions are denoted by broken circles and (4) the chlorination of monosubstituted benzenes. 

For all benzene substituents which are resonance donors, ap > ap 1. It follows from equation 23 that the differences ap 1 — ap characterizing the strengthening of the a-n conjugation increase with the enhancement of the polarizability of all the bonds within the substituent bonded to the aromatic ring. The quantitative characteristic of the overall substituent polarizability is the sum of the refractions of its bonds, E R > (see Section I). The values of ap+ and ap are approximately equal for organic substituents which are resonance acceptors. If the R3- X M substituents had only a resonance acceptor effect (the d-7T conjugation), the correlation in equation 23 would fail for compounds R3-nX MPh. In fact, equation 24... 

Positions marked B show reactivity comparable to that of ring carbons in benzene. Substituents can be introduced by electrophilic substitution reactions (Section 3.4.1.4) and show reactivity similar to those of the analogous benzene. Thus, amino groups can be diazotized (Section 3.4.3.5.3) and halogens are unreactive. 

A benzene substituent (CgHs-) is called a phenyl group, and it can be abbreviated in a structure as Ph-. 

Nitration and sulfonation of benzene introduce two different functional groups on an aromatic ring. Nitration is an especially useful reaction because a nitro group can then be reduced to an NH2 group, a common benzene substituent, in a reaction discussed in Section 18.14. 

Hall LH, Kier LB. Structure-activity relationship studies on the toxicides of benzene derivatives II. An analysis of benzene substituent effects on toxicity. Environ Toxicol Chem 1986 5 333-7. 

The nature of the benzene substituents strongly influences the fate of the reaction, controlling the position and the number of reactive double bonds. Note that at 20 °C, the norcaradienes 2 are not in equilibrium with their cycloheptatriene isomers. 

L. M., McCann, D. J., Molero, V., Reilly, J. E., Richett, M. E., Shih, C., Teicher, B., Wikel, J. H., White, W. T., Mader, M. M. Acyl sulfonamide anti-prolrferatives benzene substituent structure-activity relationships for a novel class of antitumor agents. J. Med. Chem. 2004,47(22), 5367-5380. 

The shape resonances of benzene and some of its derivatives have been explored by a number of investigators using ETS (16,17,20, 36). With the exception of questions regarding pseudo-Jahn-Teller problems (37), for example in the alkyl-benzenes, substituent effects on the doubly-degenerate ground state anion near 1.1 eV... 

As a consequence, it is not surprising that there appears to be only one isolated structure claimed. This is of the indium(I) and thallium(I) complexes with a single M—C bond from a o--bonded benzene anion that carries two bulky tri-substituted benzene substituents in ortho positions these partially block approach of other potential donors to the metal cation (Figure 4.3). An X-ray crystal structure has been determined, defining the shape. It is a rare observation, as other complexes (such as Mn(I) and Fe(I)) of the same ligand bind another ligand at the open side of the molecule, as expected. In any case, this coordination number is trivial in the sense that it can have only one shape - a linear M—L arrangement. 

Benzene Substituent Acidic medium Alkaline medium ... 

Electrophilic Attack on Derivatives of Benzene Substituents Control Regioselectivity... 

Chemistry of Benzene Substituents Alkylbenzenes, Phenols, and Benzenamines... 

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