4067-80-5Relevant articles and documents
Stereodynamics of N-Ethyl-N-methyl-2-aminopropane. 1H and 13C DNMR Studies. Molecular Mechanics Calculations
Brown, Jay H.,Bushweller, C. Hackett
, p. 11411 - 11419 (1994)
N-Ethyl-N-methyl-2-aminopropane (EMAP) is one of the simplest tertiary aliphatic amines that has a chiral center at nitrogen.Racemization occurs by inversion-rotation at the pyramidal nitrogen.For each EMAP enantiomer, additional conformational interconversions occur via isolated rotation about carbon-nitrogen bonds.The 1H and 13C dynamic NMR (DNMR) spectra of EMAP and a selectively deuterated derivative decoalesce into four subspectra at 95 K.The spectrum at 95 K is best rationalized in terms of five equilibrium conformations present at concentrations high enough to be NMR-detectable including two conformations that interchange rapidly even at 95 K.A two-letter designation is used to name the various conformations.The first letter defines the orientation of the ethyl methyl group (G denotes gauche to the lone pair and to the N-methyl group; G' denotes gauche to the lone pair and to the isopropyl group; A denotes anti to the lone pair).The second letter defines the orientation of the isopropyl methine proton (G denotes gauche to the lone pair and to the N-methyl group; G' denotes gauche to the lone pair and to the ethyl group; A denotes anti to the lone pair).The major subspectrum at 95 K is assigned to a family of G'G' and GG' conformations (59percent) that interconvert rapidly at 95 K.The other three subspectra are assigned to the GG (34percent), AA (5percent), and GA (2percent) conformations.Simulations of the DNMR spectra reveal a barrier to inversion-rotation at nitrogen (ΔG(excit.) = 7.5 kcal/mol at 160 K) that is higher than the barriers for a number of observable isolated rotations about the N-CH2 and N-CH bonds (ΔG(excit.) = 4.7-6.4 kcal/mol).A 5000-point optimized energy surface computed as a function of two dihedral angles by using Allinger's MM2(87) computer program, MM2(87) energy calculations for all the optimized equilibrium conformations of EMAP, and MM2(87)-calculated isolated rotation barriers show excellent agrreement with the DNMR data.
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Shiner
, p. 5285,5287 (1952)
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DEUTERIUM-SUBSTITUTED OXADIAZOLES
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Paragraph 00168, (2016/10/31)
Described are deuterated modulators of S1P1 receptors, pharmaceutical compositions thereof, and methods of use thereof.
Mechanism of Elimination Reactions. 38. Why Is the Effect of Successive β-Alkyl Substitution on the Rates of Elimination from Quaternary Ammonium Salts Nonadditive?
Wu, Shune-Long,Tao, Yu-Tai,Saunders, William H.
, p. 7583 - 7588 (2007/10/02)
Possible reasons are examined for the nonadditivity of the effect of successive β-methyl substitution on the rates of elimination reactions of quaternary ammonium salts.The temperature dependences of the deuterium isotope effects in E2 reactions of R1R2NMe2+ show that tunneling is not a significant source of nonadditivity.Neither is a change of gross mechanism or stereochemistry, for studies with C4H9CHDCHDNMe3+ and C4H9(CH3)CHCHDNMe3+ show the reactions to be very predominantly (>88percent) anti-E2 in both cases.Secondary tritium isotope effects with R1R2CHCHTNMe3+ increase, however in the order ethyl (1.108 +/- 0.002), propyl (1.150 +/- 0.015), isobutyl (1.216 +/- 0.012).This result suggests increasing rehybridization at the α-carbon in the transition state and therefore a shift toward less E1cB and more central-E2 character.Since methyl substitution is expected to favor a developing double bond, the much smaller rate-depressing effect of the second β-methyl is accounted for by such a shift in transition-state character.
