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Computational and Matrix Isolation Studies of Tetra‐ tert ‐butylethane
Author(s) -
Bucher Götz
Publication year - 2009
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200900378
Subject(s) - chemistry , steric effects , alkane , matrix isolation , xenon , yield (engineering) , tetra , enthalpy , photochemistry , decomposition , methane , molecule , organic chemistry , medicinal chemistry , hydrocarbon , thermodynamics , physics
Irradiation of cryogenic xenon matrices containing the sterically congested alkane tetra‐ tert ‐butylethane ( 1 ) with intense pulses from a KrF excimer laser ( λ exc = 248 nm) have resulted in the formation of methane and isobutene as the major products. Larger fragments derived from 1 , such as 2,2‐dimethylbutane ( 10 ), were also detected, whereas no evidence was obtained for the formation of the elusive tetra‐ tert ‐butylethylene ( 2 ). The results suggest that biphotonic irradiation of xenon matrices containing tert ‐butylated precursor molecules may generally result in the efficient formation of isobutene and smaller alkanes. An analysis of the decomposition reactions of 1 by various computational methods revealed that commonly used DFT methods, such as B3LYP or BLYP, and MP2 theory do not provide a good description of the energetics of the decay reactions of the sterically overloaded alkane 1 . The recently developed M05‐2X method was the only method among those tested to yield an activation enthalpy for the cleavage of 1 in agreement with the experimental value.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)