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Enolate anions halogenation involving

The methyl group of a methyl ketone is converted into an a ,a ,a -trihalomethyl group by three subsequent analogous halogenation steps, that involve formation of an intermediate enolate anion (4-6) by deprotonation in alkaline solution, and introduction of one halogen atom in each step by reaction with the halogen. A... [Pg.149]

Thus, ketone enolates easily substitute chlorine in position 2 of the electrophilic nucleus of pyrazine (1,4-diazabenzene), and even in the dark, the reaction proceeds via the Sj l mechanism (Carver et al. 1981). It is expected that the introduction of the second chlorine in the ortho position to 4-nitrogen in the electrophilic nucleus of pyrazine promotes the ion-radical pathway even more effectively. However, 2,6-dichloropyrazine in the dark or subjected to light reacts with the same nucleophiles by Sr.,2 and not S nI mechanism (Carver et al. 1983). The authors are of the opinion that two halogens in the pyrazine cycle facilitate the formation of a-complex to the extent that deha-logenation of anion-radicals in solution and a subsequent nucleophilic attack of free pyrazine radical become virtually impossible. Thus, the reaction may either involve or exclude the intermediate a-complex, and only special identification experiments can tell which is the true one. [Pg.223]

The reaction involves an attack by the tellurium anion at the halogen atom followed by a rapid elimination of ketene from the resulting enolate. [Pg.160]

The above mechanism for the acid-catalyzed formation of the enol accords with Lapworth s interpretation of the halogenation, but for basic catalysis some modification is necessary. The proposed mechanism involves the anion (II) as an intermediate in the formation of the enol,... [Pg.166]


See other pages where Enolate anions halogenation involving is mentioned: [Pg.128]    [Pg.128]    [Pg.242]    [Pg.944]    [Pg.128]    [Pg.83]    [Pg.103]    [Pg.342]    [Pg.685]    [Pg.346]    [Pg.291]    [Pg.340]    [Pg.457]    [Pg.944]    [Pg.340]    [Pg.370]    [Pg.185]    [Pg.788]    [Pg.146]   
See also in sourсe #XX -- [ Pg.356 ]




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Enolate anions

Enolate anions halogenation

Enolates anion

Enolates anionic

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