The rotation-inversion dichotomy in trialkylamines. Direct proton DNMR observation of distinctly different rates of nitrogen inversion and carbon-nitrogen bond rotation in isopropylmethylethylamine

Abstract

Examination of the 'H[zH] D N M R spectrum of (isopropyl-2-d)(methyl-d3)(ethyl-2,2,2-d3)amine in CBrF3 reveals for the first time in an acyclic trialkylamine two distinctly different coalescence phenomena one of which can be assigned to nitrogen inoersion (AH* = 8.3 f 0.5 kcal/mol; AS* = 5.5 f 4.0 gibbs; AG* = 7.5 f 0.2 kcal/mol at -1 21.3 "C) and the other to C-N bond rotation (AH* = 5.3 f 0.3 kcal/mol; AS* = -3 f 2 gibbs; AG* = 5.6 f 0.2 kcal/mol at -157.8 "C).

Concurrent hypermethylation of multiple tumor-related genes in gastric carcinoma and adjacent normal tissues

“…(1)]. This base features one of the simplest amines with a stereogenic nitrogen atom and its behavior has been closely examined in solution 3, 4. The nitrogen atom inverts rapidly at room temperature, a motion that can be frozen out at low temperatures.…”

Isolation of an Acid/Base Complex in Solution Puts the Brakes on Nitrogen Inversion

“…(1)]. This base features one of the simplest amines with a stereogenic nitrogen atom and its behavior has been closely examined in solution 3, 4. The nitrogen atom inverts rapidly at room temperature, a motion that can be frozen out at low temperatures.…”

Asymmetric synthesis of N-stereogenic molecules: diastereoselective double aza-Michael reaction

“…1 As a consequence of fast racemization via N-inversion of the trigonal pyramidal geometry (e.g. for (isopropyl-2-d)(methyl-d 3 )(ethyl-2,2,2-d 3 )amine, DG ‡ = 31.4 kJ mol À1 ), 2 amines with three different substituents usually show no optical rotation. However, there are molecules in which such rapid conversion can be suppressed.…”