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Electrophilic Aromatic Substitution of Groups other than Hydrogen. Part I: Ipso Factors and Rate‐Limiting Steps in Dehalogenations by Diazonium Ions. 26th communication on diazo coupling reactions
Author(s) -
Fischer P. B.,
Zollinger H.
Publication year - 1972
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19720550633
Subject(s) - chemistry , diazo , substitution reaction , limiting , aqueous solution , electrophile , medicinal chemistry , ion , sulfonic acid , reaction rate constant , electrophilic substitution , group (periodic table) , inorganic chemistry , electrophilic aromatic substitution , organic chemistry , kinetics , catalysis , engineering , physics , quantum mechanics , mechanical engineering
Abstract The rates of substitution of the group X in 1‐X‐2‐naphthol‐6‐sulfonic acids (X = H, Cl, Br, and I) by p ‐chlorobenzenediazonium ions in aqueous solution have been measured. The rates of the halogenated naphthols relative to that of the parent compound (X = H) are 0.0070:0.0089:0.149 for X = Cl, Br, and I respectively. The reaction of 1‐bromo‐2‐naphthol‐6‐sulfonic acid is catalysed by thiosulfate ions; the relative rate observed for this compound does not, therefore, represent the ipso factor. It is postulated that in its substitution the release of the electrofugal leaving group (Br ⊕ ) is rate‐limiting.