The Polymerization of Olefins. VIII.¹ The Depolymerization of Olefins in Relation to Intramolecular Rearrangements. II²

Synthetic Applications of the Carbonyl Generating Grob Fragmentation

“…In 1945, fragmentation was also observed in the dehydration of di- tert -1,3-diols, which resulted in a C−C bond cleavage to ketones and olefins (Scheme ). , In analogy to the dehydration of di- tert -butylcarbinol 1 , an ionic mechanism is assumed. One hydroxyl group of 7 is transformed into a leaving group by protonation, which after H 2 O elimination leads to carbocation 9 .…”

Experimental and Theoretical Evaluation of Energetics for Nucleophilic Solvent Participation in the Solvolysis of Tertiary Alkyl Chlorides on the Basis of Gas Phase Bridgehead Carbocation Stabilities

“…4-Chloro-4-ethyl-2,2-dimethylhexane ( 6 Cl). The precursor alcohol, 3-ethyl-5,5-dimethylhexan-3-ol ( 6 OH), was prepared from 3-pentanone and neopentyllithium. The crude product was purified by medium-pressure liquid chromatography (SiO 2 , hexane−ether 3:1) and then distilled to give a colorless liquid: bp 67.5−68.5 °C/13 mmHg: 13 C NMR (CDCl 3 , 67.94 MHz) δ 8.1(CH 3 ), 31.4 (C), 31.8 (CH 3 ), 32.3 (CH 2 ), 50.3 (CH 2 ), 76.4 (C).…”

“…The alcohol was hydrochlo-rinated with HCl in a mixture of pentane and CH2Cl2 at 0 °C until HCl absorption ceased.The reaction mixture containing small amounts of white crystals was dried (CaCl2) and the solvent was evaporated to give a pale yellow solid, which was recrystallized from pentane at dry ice temperature to give 5Cl as white needles: mp 53-54 °C: 13 4-Chloro-4-ethyl-2,2-dimethylhexane (6Cl). The precursor alcohol, 3-ethyl-5,5-dimethylhexan-3-ol (6OH), 23 was prepared from 3-pentanone and neopentyllithium. The crude product was purified by medium-pressure liquid chromatography (SiO2, hexane-ether 3:1) and then distilled to give a colorless liquid: bp 67.5-68.5 °C/13 mmHg: 13 C NMR (CDCl3, 67.94 MHz) δ 8.1(CH3), 31.4 (C), 31.8 (CH3), 32.3 (CH2), 50.3 (CH2), 76.4 (C).…”

Einfluss der γ‐Verzweigung auf Solvolysegeschwindigkeit und Fragmentierung von Alkyl‐ und Cycloalkyl‐Halogeniden und ‐Arylsulfonaten. Fragmentierungsreaktionen, 8. Mitteilung

“…Beispielsweise erleidet das bei der sauren Dehydratisierung von Di-t-butylcarbinol (5) bei 200" durch Umlagerung gebildete Carbonium-Ion 6 zum Teil eine Fragmentierung gemass b) [8]. I n ahnlicher Weise ist die Bildung von Isobuten bei der Behandlung von Tri-t-butylcarbinol (7) mit Halogenwasserstoffsauren zu erklaren [9].…”