2-Methylenebornane and 2-methyl-2-bornene have previously been identified as dehydration or degradation products of 2-methylisoborneol (MIB), a compound responsible for taste and odour problems in various water environments. Previously, the identification of these products has been based on mass spectral analysis only. The dehydration of MIB under a variety of conditions was reinvestigated and the products fully characterised by 1H and 13C n.m.r. and GC-MS. Comparison of EI mass spectra of the dehydration products of MIB with those published previously indicate that earlier assignments of MIB dehydration products are incorrect. 2-Methylenebornane and 2-methyl-2-bornene have previously been identified as dehydration or degradation products of 2-methylisoborneol (MIB), a compound responsible for taste and odour problems in various water environments. Previously, the identification of these products has been based on mass spectral analysis only. The dehydration of MIB under a variety of conditions was reinvestigated and the products fully characterised by 1H and 13C n.m.r. and GC-MS. Comparison of EI mass spectra of the dehydration products of MIB with those published previously indicate that earlier assignments of MIB dehydration products are incorrect.
Reactivity of phosphonium diylids with aldehydes and ketones
Non-stabilized and semi-stabilized phosphonium diylids of the type (C6H5)2P(CHR)(CHLiR) (5) show a greater nucleophilic reactivity toward carbonyl compounds than the corresponding monoylids (C6H5)2P(CHR)(CH2R) (8).Thus diylid 5a reacts readily at room temperature with sterically hindered ketones such as fenchone or di-t-butylketone.However, the residual negative charge in the intermediate adduct 13 slows the decomposition to Wittig products and is probably responsible for the observed changes (generally enhancement) in the E-selectivity in the case of non-stabilized as well as semi-stabilized ylids.