3) Chemical stability. Aliphatic diazirines undergo thermal decomposition into nitrogen and carbenes. Therefore, we next checked the stability of the synthesized trifluoromethyl diazirines. All compounds 1g‧HCl-11g‧HCl, crystalline white solids. They were air We stored them at room temperature in closed vials on the shelf for three months and observed no detectable decomposition according to H NMR. Upon heating below 100 °C, all compo remained stable. Visual decomposition was observed at temperatures >120 °C with the elimination of nitrogen. Treatment of representative amines 2g, 6g, and acid, or aq. 1M sodium hydroxide at room temperature for one hour also did not lead to any decomposition 4) Basicity of amines. Having synthesized the needed products, we next studied the influence of the trifluoromethyl fragment on the basicity of the nitrogen atom. For that, we experimentally measured pK a values of hydrochlorides standard titration method (Figure ). Incorporation of the trifluoromethyl-diazirine unit at the β decreased its basicity by more than two orders of magnitude: p (16‧HCl) = 11.3 vs pK a (1g‧HCl) = 8.8. A similar effect was observed during the incorporation of the trifluoromethyl unit at the β-position of the pyrrolidine ring nitrogen atom decreased by more than two orders of magnitude: pK a (17‧HCl) = 11.3 vs pK a (2g‧HCl) = 9.1. Introduction of the trifluoromethyl-diazirine fragment at the α pyrrolidine ring led to an even more dramatic increase of basicity by more than four orders of magnitude: p pK a (4g‧HCl) = 7.1. A similar trend was observed with piperidine (18): incorporation of the trifluoromethyl distal γ-position (6g) led to a decrease in basicity by ca. one magnitude of order, at the β-position ( the α-position (10g) -by more than four magnitudes of order: p (19‧HCl) = 11.2 vs pK a (6g‧HCl) = 9.7 (10g‧HCl) = 6.9. HCl, 13‧HCl, and 15‧HCl were crystalline white solids. They were air-stable and moisture-stable. We stored them at room temperature in closed vials on the shelf for months and observed no detectable decomposition according H NMR. Upon heating below 100 °C, all compounds also remained stable. Visual decomposition was observed at temperatures >120 °C with the elimination of nitrogen. Treatment and 8g with aq. 1M hydrochloric acid, or aq. 1M sodium hydroxide at room temperature for one our also did not lead to any decomposition.