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Electrophilic displacement

This view is supported by the fact that if diazominobenzene is dissolved in dimethylaniline in the presence of the hydrochloride of the latter, the main product is p-dimethylamino-azobenzene, CgHjN=NCgHgN(CH3)2 this is because dimethylaniline couples in the nucleus more readily than does aniline. The reaction is an electrophilic displacement of hydrogen by the diazonium ioii ... [Pg.622]

Aromatic compounds may be chlorinated with chlorine in the presence of a catalyst such as iron, ferric chloride, or other Lewis acids. The halogenation reaction involves electrophilic displacement of the aromatic hydrogen by halogen. Introduction of a second chlorine atom into the monochloro aromatic stmcture leads to ortho and para substitution. The presence of a Lewis acid favors polarization of the chlorine molecule, thereby increasing its electrophilic character. Because the polarization does not lead to complete ionization, the reaction should be represented as shown in equation 26. [Pg.510]

The carbonium ion rearrangement is essentially an internal displacement reaction in which a carbonium ion becomes bonded to some other portion of the same molecule. Certain base-catalyzed rearrangements have been discussed in the section on carbonium ion rearrangements because they have the distinguishing characteristic of being internal electrophilic displacements by an atom bearing at least a partial positive charge. [Pg.227]

Alkylaryldichlorogermanes produce substituted cyclogermanes. In the case shown in reaction 9, three of the four possible configurations of the tetragermane product 29 are formed, but none is all-c/s. It is possible to carry out an electrophilic displacement of the phenyl groups to form the 1,2,3,4-tetrachloro derivative 30, which is aW-lrans, the configuration of 29 notwithstanding120. [Pg.356]

In complete parallel to the discussion in Section 3.5, the conditions for forming a stable 2c->-lc complex or T-bonded compound are intimately related to those for catalyzing the corresponding electrophilic displacement reaction. Thus, the implications of 3c/2e T-bonding go far beyond the chemistry of boron compounds. [Pg.319]

In Lambert s approach, the triarylstannylium ion is generated by the reaction of an electrophile with an allyltri-arylstannane. The bulky aryl groups sterically protect the tin center in the stannylium ion from attack by nucleophiles, yet the allyl ligand permits unhindered conjugate electrophilic displacement of the tin (Equation (42)).145... [Pg.821]

Compound 21d reacted with bromine in carbon tetrachloride to give 76g in high yield, probably by electrophilic displacement of nitrogen and subsequent combination of the bromide with the carbocation (64JOC3577). [Pg.120]

Electrophilic substitution reactions are those where an electrophile displaces another group, usually a hydrogen. Electrophilic substitution occurs in aromatic compounds. [Pg.232]

The electrophilic displacement mechanism for catalystic cracking is further confirmed by the negative slopes of the Hammett and Taft correlations (Table 14) and has been supported by MO calculations in which electrophilic, nucleophilic and free radical mechanisms were compared [228]. [Pg.318]

When 2,4,6-trimethylpyrylium perchlorate is heated with [0-2H]acetic acid, the 3- and 5-hydrogens are deuterated. This substitution is unlikely to occur by direct electrophilic displacement in the cyclic compound but may proceed through an acyclic dienone formed by prior addition of acetate ion at C-2 (69RRC247). [Pg.649]

Mercury(II) chloride also forms a 1 1 complex with 3-methyloxa-diazole, which in a buffered solution forms a new complex with the electrophilic displacement product [Eq. (67)]. [Pg.104]

Some of the most important electrophilic displacement reactions of lignins are listed in Table I with the reactive species indicated. In general, the complexity of the products from these reactions makes structural evaluation extremely difficult. Therefore, an approach using model compounds related to lignin appears desirable. [Pg.51]

Table III summarizes the observed rate constants, some of which were determined in 57% perchloric acid solution. It is interesting to note that the ortho and para positions of phenol are slightly less reactive towards protodedeuteration than those of anisole. In most electrophilic displacement sections the reverse order is observed. Table III summarizes the observed rate constants, some of which were determined in 57% perchloric acid solution. It is interesting to note that the ortho and para positions of phenol are slightly less reactive towards protodedeuteration than those of anisole. In most electrophilic displacement sections the reverse order is observed.
Obviously then, the relative reactivities of the aromatic positions in lignin units do not fit a uniform pattern but depend largely on the specific nature of the electrophile. Consequently, the information obtainable from protodedeuteration data is somewhat limited at the moment. Since the protodedeuteration rate constants can be determined conveniently and precivSely, they can probably be used better in the future to predict reactivities in other electrophilic displacements as the interrelations between these reactions become more thoroughly understood. [Pg.61]

Bromosilatrane (50) can be involved in electrophilic displacement reactions with silver compounds26,27 to give products 21, 37, 61 and 62 (equations 77-80). [Pg.1489]

Again, reaction (43) occurs subsequent to the bimolecular electrophilic displacement (47). [Pg.207]

Under Friedel-Crafts-type conditions, many electrophilic displacements of the silyl moiety occur, so l-phenylsulfonyl-2-TMS-ethyne (49) can be prepared from 12 with benzenesulfonyl chloride in presence of catalytic amounts of aluminum chlo-... [Pg.37]


See other pages where Electrophilic displacement is mentioned: [Pg.13]    [Pg.170]    [Pg.171]    [Pg.122]    [Pg.229]    [Pg.95]    [Pg.44]    [Pg.257]    [Pg.231]    [Pg.836]    [Pg.226]    [Pg.350]    [Pg.93]    [Pg.93]    [Pg.51]    [Pg.51]    [Pg.52]    [Pg.52]    [Pg.52]    [Pg.54]    [Pg.56]    [Pg.58]    [Pg.60]    [Pg.62]    [Pg.112]    [Pg.254]   
See also in sourсe #XX -- [ Pg.258 ]




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