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

Abstract

Three diastereomeric hydrocarbons 7 were formed on reaction of 1 -adamantyl-1 ,1 -dibromo-2.2-dimethylpropane with magnesium. They were separated by fractional crystallization and identified by 'H NMR spectroscopy and X-ray crystallography as meso-7 and the two rotamers of D , L -~ mentioned in the title. They are the first examples of simple aliphatic hydrocarbon rotamers, which do not interconvert at room temperature and above. Analogous 1-norbornyl derivatives were also obtained but could not be separated. The kinetics and the products of thermolysis of these hydrocarbons were investigated.Thermolabile Kohlenwasserstoffe, XXVIII 1.2) Trennnng, Struktnranalyse und Thermolyse eines stabilen Rotamerenpaares; P-(R*,R*)-und M-(R*,R*)-o.~-3,4-Di-l-adamantyl-2,2,5,5-tetramethylhexan Aus 1-Adamantyl-1 ,l-dibrom-2,2-dimethylpropan erhielt man bei der Umsetzung mit Magnesium drei diastereomere Kohlenwasserstoffe 7, die durch fraktionierte Kristallisation getrennt werden konnten. Sie wurden durch NMR-Spektroskopie und Kristallstrukturanalyse als meso-7 und die rotameren Titelverbindungen 7 erkannt. Es handelt sich um das erste Beispiel bei Raumtemperatur und dariiber nicht interkonvertierender, einfacher aliphatischer KohlenwasserstoffRotamere. Die analog hergestellten 1-Norbornylderivate konnten nicht getrennt werden. Die Thermolyse der Verbindungen wurde kinetisch und praparativ studiert.For a bond connecting two tertiary carbons (C, -C, systemsz)) in aliphatic hydrocarbons gauche-conformations 2 are preferred over anti-conformations 12). 3--

Enthalpies of Formation of Hexaethylethane, Octamethylhexane, and Tri-tert-butylmethane. Extremely Strained Hydrocarbons

“…Intramolecular van der Waals repulsions are responsible for this excess energy, the so-called strain energy, which causes unique structural distorsions . Elongated bonds up to 165 pm4b are found especially between two quaternary carbon atoms 4 and enlarged bond angles (to more than 120°) at tertiary carbons …”

Crystal structure of and conformational equilibria in 1,1′‐dihydroxybis(4H‐cyclopenta[def]phenanthrene) and related derivatives

“…A higher boiling solvent (DMSO) was used for the high-temperature NMR spectra. The room temperature 1 H NMR spectrum of 1 in this solvent is similar to that in CDCl 3 . The high-temperature spectrum of 1 at 82°C gave three signals in the aromatic region (υ 7.0-7.8 ppm) with relative intensities of 4 : 2 : 2.…”

“…Examples of this class of compounds include the triptycenes which are substituted with a bulky tertiary or secondary carbon at the bridgehead position, 1,2 and other tetrasubstituted ethanes carrying bulky substituents. 3,4 Electronic effects such as intramolecular hydrogen bonding in vicinal diols can further restrict rotation about carbon-carbon -bonds, although such interactions are not as energetically strong as hydrogen bonding in 1,3-diols where the more ideal six-centered arrangement can be achieved. 5 Nevertheless vicinal diols contain the highest proportion of intramolecular H-bonded conformers.…”

Consequences of Strain for the Structure of Aliphatic Molecules

“…These were obtainable either by Wurtz type reactions [26,[36][37][38][39] [20.28,36] [Reaction (c), [36' (d) t Bu-C-N=N-C-t Bu --> t Bu-C-C-t Bu…”