The Activation Energy of Inversion in Substituted 1-Methylaziridines (N-Methylethylenimines) Measured by the Nuclear Magnetic Resonance Technique¹

The Rate of the Chair-Chair Interconversion of Cyclohexane

“…All chemical information suggests that this interconversion is rapid, and estimates based upon qualitative energetics4 and upon spectroscopic assignments6 have been made. Shoppee estimated the barrier to be 9-10 kcal./mole and Beckett, Pitzer and Spitzer estimated the barrier to be 14 kcal./mole.…”

N.m.r. Studies of rate processes and conformations. Part VI. Ring inversion in hexahydro-1,3,5-triazines

“…If, similarly, allowance is made for the transmission coefficient of $ the AG* values in Table 2 must be corrected by subtracting ca. 0.3 k~al./mole.~' SoZvent E$ects.-It has been found that the barrier to nitrogen inversion in aziridines 23 and in diaza-bicyclic systems la increases by ca. 2 kcal./mole on changing from pure liquid or pentane solution to solutions in D,O.…”

Hindered nitrogen inversion in N-halogenoaziridines and in N-halogenoazetidines

“…These results show that in the N-halogenoaniines (VI) and (VII) [and therefore also in (11) and in (111)] nitrogen inversion is very slow at 30" and that the inversion barrier (as measured by AG:) is very high (see Table ). In comparison, a AGz value of ca.…”

“…This also represents the first study of hindered nitrogen inversion in azetidines .' The N-halogeno-amines (11) and ( 111), (VI) and (VII), and (X) and (XI) have been prepared by treatment of the amines (I), (IV), and (VIII)* with a solution of the corresponding hypohalite.D The n.m.r. spectrum of (11) has been reported to be a single line a t 20 MHz.…”