Kinetic applications of electron paramagnetic resonance spectroscopy. XIII. Di-tert-butylmethyl and related radicals

Abstract

42%). The latter structure was based on the nmr spectrum of the crude reaction product which showed a quartet at 6.09 (J = 7.5 Hz, vinylic) and a doublet at 2.12 ppm (J = 7.5 Hz, C/73CH=) and formation of 9-isopropyl-10-ethylanthracene from acid-catalyzed rearrangement of the crude product. Isomerization took place under the conditions employed in the preceding example to afford a crude product (0.61 g) shown by glpc and nmr to contain 9-isopropyl-10-ethylanthracene (40%). Chromatography on alumina followed by crystallization from petroleum ether gave pure 9isopropyl-10-ethylanthracene: mpllO-1110; nmr(CC14) 1.45(t, 3,

Computational and Matrix Isolation Studies of Tetra‐tert‐butylethane

“…of 14 of Δ H ‡ rec = 8.2 kcal mol –1 . Note that this latter value is significantly below the lower limit for the activation enthalpy (Δ H ‡ rec,exp ≥ 22.9 kcal mol –1 ) reported by Ingold and co‐workers 19…”

“…Among the methods tested, only the M05‐2X method appears to achieve the correct balance between attractive and repulsive intramolecular interactions in this molecule. Although the M05‐2X results are in excellent agreement with the thermochemical data for 1 published by Rüchardt and co‐workers,8 they are clearly inconsistent with the lower limit for the activation enthalpy for the dimerization of the di‐ tert ‐butylmethyl radical 14 , as measured by Ingold and co‐workers employing ESR spectroscopy 19. At present, no explanation for this discrepancy can be offered 22…”

Frank C. Whitmore and steric hindrance: A duo of centennials

“…The connection of radical stability with steric bulk was apparent to Conant in the 1920's (9) and was explicitly pointed out by Bartlett and Schneider in 1945 (30), who drew attention to the obvious interest in the preparation of tri-£er£-butyl radical, as the dimeric hexa-tert-butylethane would be prohibitively strained. This prediction was confirmed when the radical was eventually prepared by Ingold and co-workers, as the molecule showed no tendency for dimerization (eq 17) (33).…”

Thermolabile hydrocarbons, XXVIII. Separation, structure analysis, and thermolysis of a pair of stable rotamers; P‐(R*,R*)‐ and M‐(R*,R*)‐D,L‐3,4‐di‐1‐adamantyl‐2,2,5,5‐tetramethylhexane

“…1.5 g (33%) colourless oily liquid remained which, according to NMR, consisted of 47% of meso-8 and 53% of the two D , L -~ rotamers in a 2: 1 ratio. I, I , 2 , 2 -T e t m -I~& m a n~l e t~~ (6): Di-1 -adamantyl ketone32) and di-l-adamantyIrnethanoP)…”