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The factors which are responsible for the preferential exchange of one diastereotopic proton over another have been examined in studying a series of benzyl alkyl sulfoxides. Comparison of relative rates with stereochemistry shows that at least two effects contribute to the observed results. These are the orientation of the carbanion with respect to the lone pair on sulfur and with respect to the benzene ring.
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The factors which are responsible for the preferential exchange of one diastereotopic proton over another have been examined in studying a series of benzyl alkyl sulfoxides. Comparison of relative rates with stereochemistry shows that at least two effects contribute to the observed results. These are the orientation of the carbanion with respect to the lone pair on sulfur and with respect to the benzene ring.
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Nous avons synthétisé quelques composés dans la série du phtalide et du phenyl-3 phtalane, substitués en position para au groupement méthylène. Les résultats obtenus en RMN montrent que les déplacements chimiques des protons du groupement méthylène sont en relation linéaire avec les valeurs d'Hammett. Des résultats semblables ont été obtenus pour les constantes de couplage des protons méthyléniques dans la série du phtalane. On discutera brièvement de la possibilité d'appliquer ces relations à la conformation de la molécule.
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Of the many methods which have been used to synthesize benzyne, most of them have involved elimination of an anion in the final step. We have obtained evidence for the formation of benzyne by elimination of a cationic group. Ortho-amino-triphenyl carbinol gives on diazotization in acetic acid, benzophenone and phenyl acetate, in addition to 9-phenyl-fluorenol, the product of ring closure.
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The assignment of configuration to substituted olefines can be made by n-m-r spectroscopy. Three different methods of assignment have been reported recently, each one limited to certain types of olefines. A fourth method of distinguishing between cis and trans isomers appears valid from an examination of the spectra of a series of α-β unsaturated carbonyl compounds.
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The assignment of configuration to substituted olefines can be made by NMR spectroscopy. Three different methods of assignment have been reported recently, each one limited to certain types of olefines. A fourth method of distinguishing between cis and trans isomers appears valid from an examination of the spectra of a series of α-β unsaturated carbonyl compounds.
