Aromatic nucleophilic substitution reactions in high temperature, high pressure water
- Los Alamos National Lab., NM (United States)
Aromatic nucleophilic substitution reactions in anoxic supercritical water were examined both for their synthetic and waste remediation potential. The substrates were halogenated aromatic compounds, and the nucleophiles were hydroxide and halide salts. Hydroxide reacts rapidly with bromo-, chloro-, and fluorobenzene at 400{degrees}C and 5300 psi, and phenol is produced almost quantitatively. In batch studies, the reaction rate order was bromo > fluoro > chlorobenzene. Mechanistic studies using halogenated toluenes showed that fluorotoluenes yield ipso substitution, possibly via the S{sub N}Ar mechanism, Chlorotoluenes and bromotoluenes yield cine substitution, likely via the benzyne mechanism. Sodium chloride reacts with bromotoluenes to yield ipso-substituted chlorotoluenes as the major product; cesium fluoride yields cine substituted cresols as the major products, with small amounts of cine substituted fluorotoluenes. The results indicate that fluoride is a very strong base under supercritical conditions, and that the benzyne mechanism results. Chloride is a weaker base and reacts by a direct substitution mechanism such as S{sub N}Ar.
- OSTI ID:
- 126732
- Report Number(s):
- CONF-950402--
- Country of Publication:
- United States
- Language:
- English
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