57321-17-2Relevant academic research and scientific papers
1,3,5-Trineopentylbenzene and Related 1,3,5-Trialkylbenzenes Containing Groups with Both Steric and Conjugative Effects. 1H NMR Band Shape and 13C Spin Lattice Relaxation Time Measurements and Force Field Calculations
Anderson, Sven,Carter, Robert E.,Drakenberg, Torbjoern
, p. 579 - 596 (2007/10/02)
2,4,6-Trialkylsubstituted styrenes, benzaldehydes and N-methylbenzaldimines were studied by the 1H NMR band shape and 13C spin lattice relaxation time techniques.The results were in most cases found to be well reproduced by molecular mechanics calculations with the Allinger MMP1 and MMP2 programs.In the case of 2,4,6-trineopentylstyrenes, it was found that a cis-β-vinylic methyl group is responsible for the high barrier to internal rotation (74 kJ mol-1) observed.The compound with a trans-β-vinylic methyl group has a barrier (-1), of similar magnitude to that of 2,4,6-trineopentylstyrene itself.For the benzaldehydes and N-methylbenzaldimines, an upper limit to the barrier of -1 in all cases was estimated by 13C spin lattice relaxation time measurements.A model involving free diffusion in a restricted range was used to calculate internal correlation times from T1 data.The influence of librational motions on rotational barriers from spin lattice relaxation time measurements is discussed.
