Structural and Energetics Studies of Tri- and Tetra-tert-butylmethane

Abstract

Applying the G3 and G3(MP2) models and using both the isodesmic and atomization schemes, the heats of formation (ΔH f) at 0 and 298 K are calculated for mono-tert-butylmethane (2,2-dimethylpropane or neopentane, abbreviated as mono-TBM), di-tert-butylmethane (di-TBM), tri-tert-butylmethane (tri-TBM), and tetra-tert-butylmethane (tetra-TBM). Upon examining the results, it is found that all of the calculated ΔH f298 values are well within ±10 kJ mol-1 of the available experimental data for the first three compounds. Hence, for tetra-TBM, a compound that has not yet been synthesized, the G3(MP2) results reported in this work should be reliable estimates. Moreover, we have found that the atomization scheme is slightly more suitable for the study of the smaller molecules, while the isodesmic scheme is more suitable for the larger molecules. Structurally, it is found that the equilibrium structures of mono-TBM, di-TBM, tri-TBM, and tetra-TBM have T d , C 2, C 1, and T symmetry, respectively. The energy-minimized structure of each TBM molecule is determined and all structural parameters are generally in good agreement with the available experimental data. Furthermore, it is found that the innermost C−C bond lengths increase along the series mono-TBM < di-TBM < tri-TBM < tetra-TBM, a trend that is expected from steric consideration.

Homolytic Bond Dissociation Enthalpies of C–C and C–H Bonds in Highly Crowded Alkanes

“…In these molecules, the strain energy analysis and the DFT calculations suggest that 3,3-di-tert-butyl-2,2,4,4-tetramethylpentane is the smallest saturated alkanes that can not be made. 9,[34][35][36] In present study, the innermost C-C BDE of 3,3-di-tertbutyl-2,2,4,4-tetramethylpentane (Table 4) is 71.63 kJ/mol. Taking the exceptions at very low temperatures for a short time and thermodynamic conditions, 80.00 kJ/mol is more suitable as the standard to estimate the availability of the molecules in these series.…”

Comparison of literature models for volatile product formation from the pyrolysis of polyisobutylene at mild conditions: Data analysis, free-radical mechanistic considerations, and simulation of initial product-forming pathways

“…3, we operationally define a ''strain'' as the difference between the (Boltzmann-averaged) DH f value produced by the MMX parameterization and the GA estimate [61] without correction terms. The MMX parameterization for 2244M4C5 gave DH f only 1.7 kcal mol À1 ''too stable'' compared with the experimental value [65] and reproduced the structural features well: r(C 2 -C 3 ) = 155.3 pm, u(C 2 -C 3 -C 4 ) = 124.28, and c(C 1 -C 2 -C 3 -C 4 ) = 1678 [66]. As a result of correlated twists, the terminal methyl groups are moved apart by a twist of 248 from an ideal ''eclipsed'' relationship when viewed along the C 2 -C 4 axis [67].…”

What Is the Smallest Saturated Acyclic Alkane that Cannot Be Made?

“…Molecule 2 ( Figure 1) has never been synthesized, and studies have shown that it must be extremely strained. [5][6][7] However, this is not a proof that it is impossible to prepare. Indeed, molecules which include this carbon framework, such as tetramethyltetrabenzo [5,5,5,5]fenestrane (5, Figure 2), have been synthesized.…”