H-1 and C-13 NMR spectra of betaines, N+(CH2)(n)COO-, and their hydrogen halides. Additivity rules for carbon-13 chemical shifts

The H-1 and C-13 chemical shifts of N-methylpiperidine betaines (1), C5H10N +(CH3)(CH2),COO-, and their derivatives C5H10N+(CH3)(CH2)(n)COOH.X- (2) and C5H10N+(CH3)(CH2)(n)COOC2H5.X- (3) With n = 1-5 were identified using two- dimensional homonuclear (H-1) chemical shift correlation (COSY) and heteron uclear (H-1, C-13) chemical shift correlation spectroscopy (H,C-COSY). The effects of the positively charged nitrogen and COO-, COOH, COOEt groups on the methylene protons in the tether groups [N+(CH2),COO] and the ring proto ns in 1, N-methylpyrrolidine betaines (4), pyridine betaines (6) and their hydrogen halides, were analysed. Empirical additivity rules for the C-13 ch emical shifts of tether C-1, C-2, C-3, C-4 and C-5 atoms for 1, 4 and 6 and their hydrogen halides were derived from the experimental results. The eff ect of N+ on the beta carbon vary with the ring type. Copyright (C) 2000 Jo hn Wiley & Sons, Ltd.