Phenoxide ions nucleophilic carbon atom

The eourBe of addition of phenols to epicMorohydrin has been a subject of some controversy, since one might suppose the Btrongly nucleophilic character of phenoxide ion to cause indiscriminate attack on the chlorine-substituted carbon atom and tbe epoxide ring... 

A displaces a chlorine atom from the primary carbon of epichlorohydrin.The phenoxide ion of bisphenol A is a good nucleophile, and chlorine on the primary carbon of epichlorohydrin is the leaving group. 

The compounds whose preparations are described in Experiments [Ilk], [22B], [22C], and [22D] are alkyl aryl ethers. The general method of preparation is the Williamson synthesis, an Sn2 reaction spedficaUy between a phe-noxide ion (ArO ) nucleophile and an aUcyl halide. This reaction is often used for the synthesis of symmetrical and unsymmetrical ethers where at least one of the ether carbon atoms is primary or methyl, and thus amenable to an Sn2 reaction. Elimination (E2) is generally observed if secondary or tertiary halides are used, since phenoxide ions are also bases. 

We recall that enolates undergo condensation reactions with the carbonyl carbon atom of aldehydes (Section 21.7). Enolates tend to react to give alkylation at carbon. A similar reaction occurs between the phenolate ion and formaldehyde. Because both C-2 and C-4 are nucleophilic, two possible condensation products may result. The following reaction shows condensation at C-4, producing a conjugation-extended enolate. Subsequent tautomerization generates the enol form, which is a phenol. Solvent-mediated proton transfer also occurs, giving a phenoxide rather than the more basic (and less stable) alkoxide ion. 

Transposition of substituents takes place from aromatic compounds based on ortho effects from hydroxyphenyl ketones via assumed nucleophilic attack on the carbonyl carbon atom of the phenoxide site to give a tight tetravalent intermediate that promptly decomposes through benzyne neutral release and formation of a carboxylate anion (Scheme 17.19a). This reaction is hindered from meta- and para-substituted phenols. Alternatively, radical alkane loss is also observed that can be rationalized by considering the formation of an ion-neutral complex (Scheme 17.19b) comprised of quinone-like and alkylide groups. The relatively low ionization energy allows the generation of odd-electron quinone-like species and the elimination of the alkane radical (Scheme 17.19b). 

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