Basicities of cycloalkylamines: Baeyer strain theory revisited

A new, accurate NMR titration method was utilized to determine relative bas icities in four solvents of the two norbornylamines 2 and a series of cyclo alkylamines 3-15, as well as some sec-alkyl amines. Cyclopentylamine (5) an d cyclohexylamine (6) are substantially more basic than the small rings 3-4 and slightly less basic than the medium rings 7-11, with cyclooctylamine ( 8) the most basic. The large rings 12-15 are significantly less basic than 6. The basicities reflect CCC angles, hybridization, and also solvation. Th ese results and their relationship to Baeyer strain theory are discussed. ( C) 1999 Elsevier Science Ltd. All rights reserved.