ChemInform Abstract: BARRIERS TO INTERNAL ROTATION IN TRINEOPENTYLBENZENES PART 3, NITRO‐SUBSTITUTED COMPOUNDS

Barriers to internal rotation in 1,3,5-trineopentylbenzenes. VI. Correlation between barriers to internal rotation (.DELTA.G.dag.) and substituent size

“…Recrystallization from nitromethane gave a product with mp 71-72°; yield 0.5 g (10%); mass spectrum m/e (% of base peak) 29 (17), 41 (26), 43 (22), 55 (6), 57 (100), 58 (5), 71 (9), 115 (9), 128 (6), 129 (5), 141 (6), 142 (5), 143 (7), 149 (13), 157 (5), 159 (5), 167 (6), 173 (9), 174 (7), 229 (14), 372 (78), 373 (8), 427 (5), 428 (46), 429 (7), 483 (7), 484 (35), 485 (7), 540 (21), 541 (5). The purpose of the synthesis was to obtain a sample of lj large enough to permit nmr measurements, and the reaction conditions were consequently not optimized.…”

“…However, there are apparently few molecular systems which allow such a study over a sufficiently wide range of substituent "sizes" by the same method of measurement, and which have barriers whose relative heights are primarily determined by differences in effective substituent "sizes." CH2-í-Bu [14][15][16][17] and a twisted nitro group16 and the estimamine, tion (by coalescence temperature measurement) of a barrier past fluorine. 18 In the present paper, we report work on the refinement of the re/Y-butyl-fluorine barrier, the determination of barriers past a proton, a methyl group, and an iodine atom, and an attempt to utilize the series of barriers to gain some insight into the problem of steric effects and substituent "sizes.…”