Conformations and rotation of -propyl groups attached to the same saturated carbon centre. A dynamic N.M.R. and molecular mechanics study of 1,1,1-tris--propylethane, di- -propyl--butylmethane and 1,1-di--propyl--butylethane

Conformational Dynamics of Triple Rotors: Tris(dimethylamino)methane, Triisopropylamine, and Related Molecules1

“…Substituents of the first type are encountered in published studies of tris(chloromethyl)ethane,3a triethylamine,3b and tribenzylamine 3c. With the latter two substituent types there is more congestion round the central atom, and examples already reported are triisopropylmethane, triisopropylethane, tricyclohexylmethane, and triisopropylamine . As an addition to this class we now report an analysis of triple rotors tris(dimethylamino)methane ( 1 ) and tris(diethylamino)methane ( 2 ) based on dynamic NMR measurements and molecular mechanics calculations, and we comment on studies of triisopropylamine 7 ( 3 ) and N,N- diisopropyl-3-pentylamine ( 4 ), with some further results.…”

Dynamic NMR and Computational Studies Inform the Conformational Description of Dendrillane Terpenes from the Nudibranch Goniobranchus coi

“…This led us to consider whether a rate process involving rotation about the pentasubstituted C-8/C-14 bond might be involved. The energy barrier in regular hydrocarbons is 3 kcal mol –1 , but is 5–10 kcal mol –1 in isopropyl- and tert -butyl-substituted hydrocarbons . Further information was sought from a computational study on 1 .…”

“…The energy barrier in regular hydrocarbons is 3 kcal mol −1 , but is 5−10 kcal mol −1 in isopropyl-and tert-butyl-substituted hydrocarbons. 15 Further information was sought from a computational study on 1. A Monte Carlo Multiple Minimum (MCMM) conformational search was undertaken using Macromodel (Schrodinger Inc.), 16 providing eight conformers, and selected conformers (<3 kcal mol −1 of the global minimum) were next optimized by density functional theory (DFT) calculations at the B3LYP/6-31G(d,p) level with IEFPCM chloroform solvent (Gaussian16W (Revision B.01) 17 ) (Supporting Information).…”

Insights into the chemical composition and ecology of nudibranchs of the genus Goniobranchus

“…199 The barrier to rotation in isopropyl-and t-butyl-substituted hydrocarbons is generally within 5-10 kcal mol -1 . 200 A computational investigation, carried out in parallel with the variable temperature NMR study described above, provided further insight into the origin of the conformational averaging in 3.1.…”

“…199 Conversely, the energy barrier to rotation in isopropyl-and t-butyl-substituted hydrocarbons is generally within 5-10 kcal mol -1 . 200,201 Classic examples from the natural product literature include restricted rotation about amide bonds in the sesquiterpene formamide metabolites isolated from marine sponges and their dietary molluscs, 153 as well as in peptides. 202 In amides such as N-methyl acetamide and N-methyl formamide, slow exchange at room temperature enables observation of both conformers, with an activation barrier up to ~15 kcal mol -1 .…”