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1.4 CHEMICAL SCIENCES
A simple analytical LC-MS (Liquid Chromatography Mass Spectrometry) method and associated instrumentation has been adapted for use by the organic chemist to yield mg quantities of target compound from a reaction mixture. Calixarene 3 was identified as representing 51% of total peak area of a reaction mixture containing no less than 10 components, using LC-MS. This peak corresponded to a mass of 878.8, equivalent to a complex of 3 and an ammonium cation. Molecular models further rationalise this observation by showing that the asymmetric binding cavity of 3 is suitable for binding tetrahedral guests like the ammonium ion. By scaling up the LC method, using analytical instrumentation, 55mg of 98% pure 3 were isolated with a recovery yield of 90% in 1 hr. The current method represents a powerful and easily adapted tool for monitoring a challenging synthesis which combines identification, efficient separation and partial characterisation for reaction mixture components using readily available instrumentation and methods.
Schazmann, B.(2005) Identification and recovery of an asymmetric calixarene tetranitrile derivative using liquid chromatography and mass spectrometry. Supramolecular Chemistry, 2005, 17, 393-399. DOI:10.1080/10610270500138789