Table 2.

Acid–base transitions in fluoroprolines.^a

	ammonium moiety		carboxylic acid moiety
			cis-amide conformation		trans-amide conformation
entry	structure	pKa	structure	pKa	structure	pKa
Pro		10.68		2.85		3.55
R-Flp		9.10		2.37		3.19
S-Flp		9.10		2.87		3.39
Dfp		7.15		2.34		2.93

^aDetermined in aqueous solution at 298 K. The error for the pK_a value is ±0.10 for the ammonium group and ±0.05 for the carboxylic acid group. For details see references [16,19,57–58].