Zur Frage der Isomerenbildung bei der Chlorierung von höhermolekularen Paraffinkohlenwasserstoffen mit verschiedenen Halogenierungsagenzien

Abstract

Die bei der Chlorierung von n‐Heptan, n‐Octan, n‐Decan und 2.3‐Dimethylbutan mit N‐Chlor‐succinimid, tert.‐Butylhypochlorit, Trichlormethansulfochlorid, Tetrachlorkohlenstoff, Trichlormethansulfenylchlorid, Phosphorpentachlorid sowie elementarem Chlor in den mit Chloratomen lockere Komplexverbindungen bildenden Lösungsmitteln Benzol oder Schwefelkohlenstoff resultierenden Monochloralkan‐Isomerengemische wurden quantitativ erfaßt. Dabei wurden überraschende, mit den bisherigen Erkenntnissen über die Verhältnisse bei der Substitution der Paraffinkohlenwasserstoffe nicht übereinstimmende Isomerenverteilungen festgestellt. Die Resultate ergeben sich durch das Zusammenwirken der unterschiedlichen CH‐Dissoziationsenergien der einzelnen Wasserstoffatomtypen des Alkans sowie der freien Energie des angreifenden Radikals mit polaren Effekten sowohl beim angreifenden Radikal als auch beim Paraffinkohlenwasserstoff.

Selective Alkane Transformations via Radicals and Radical Cations: Insights into the Activation Step from Experiment and Theory

“…554 Pronounced 3°C-H selectivities were found for chlorinations with the Cl 3 C radical, which is much more selective than the Cl radical and most other free-radical chlorinating agents. 555 Consequently, the 3°:2°reactivities of adamantane toward the Cl 3 C radical is 24. [556][557][558] In the absence of Cl radicals (using more easily homolyzable BrCCl 3 as the Cl 3 Cradical source), the selectivity for the adamantane chlorination is even higher (3°:2°) 27.0).…”

Chlorination of 2,3-dimethylbutane: A quantitative organic chemistry experiment

“…The use of S02C12 is preferred both for shorter reaction times (less congestion on the vpe instruments) and less selectivity (easier treatment of comparable peak areas). An additional advantage is the opportunity to demonstrate that the isomer ratio is solvent dependent (4,(13)(14)(15). Thus it is instructive to use benzene and carbon disulfide, in addition to carbon tetrachloride.1 From the vpc analysis the student, can calculate the relative amounts of 2-chloro-2,3-dimethylbutane and l-chloro-2,3-dimethylbutane and, subsequently, the relative reactivity per hydrogen at the tertiary versus the primary sites.…”

Mechanisms of the C-H halogenation of adamantane in the presence of N-hydroxyphthalimide

“…1b) when PINO ⋅ is generated from NHPI by the action of oxone and then abstracts a hydrogen atom from the AdH molecule to give an Ad ⋅ radical, which is captured by carbon tetrachloride (X-Y), forming chloroadamantane (AdX) and a trichloromethyl radical (Y ⋅ ), which then initiates another radical chain reaction. The hypothesis of the participation of the ⋅ CHal 3 in C-H bond activation finds was tested when CBr 4 is used instead of CCl 4 since the selectivity for replacement in AdH should increase in the case of chain initiation by the tribromomethyl radical ⋅ CBr 3 [8]. Functionalization of AdH in the NHPI/CBr 4 /oxidant system gave 1-bromoadamantane (2), 2-bromoadamantane (3), and dibromoadamantane (4) functionalization of AdH in the NHPI/CBr 4 /oxidant system is enhanced (3°/2°= 25-30), which is characteristic for radical reactions involving ⋅ CBr 3 .…”