The gas-phase structures of some highly strained compounds: di-t-butylmethane, di-t-butylamine and di-t-butyl ketone

Liedle, Siegfried; Oberhammer, Heinz; Allinger, Norman L.

doi:10.1016/0022-2860(93)07850-v

Cited by 13 publications

(5 citation statements)

References 12 publications

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“…20 Furthermore, our results are also in agreement with those obtained by MM3 and lower level ab initio methods. 24 It is also noted here that the C t -C q bond (1.547 Å) of di-TBM is longer than the C t -C m bond (1.528 Å) of mono-TBM. The lengthening of the innermost C-C bonds indicates the increase of strain from mono-TBM to di-TBM.…”

Section: Di-tert-butylmethane (Di-tbm)supporting

confidence: 57%

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

Cheng

2003

J. Phys. Chem. A

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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.

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Section: Di-tert-butylmethane (Di-tbm)supporting

confidence: 57%

“… a Reference 20. b Data for mono- and di-TBM are experimental results taken from ref . Data for tri- and tetra-TBM are spectroscopically determined force field (SDFF) results taken from ref .…”

Section: Methods Of Calculation and Resultsmentioning

confidence: 99%

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

Cheng

2003

J. Phys. Chem. A

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“…The MM4 value agrees well with the MP2/BC value (125.7 vs. 125.48, Table10). When we compare the MM4 value with the more recent electron diffraction (r g ) 62 value, the agreement is poor (125.7 and 129.08 (20), respectively), but the experimental uncertainty is rather large. One can also examine the distances between the two tertiary carbons as determined by the different methods.…”

Section: Di-t-butylaminementioning

confidence: 86%

Molecular mechanics (MM4) study of amines

et al. 2007

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The MM4 force field has been extended to include aliphatic amines. About 20 amines have been examined to obtain a set of useful molecular mechanics parameters for this class. The vibrational spectra of seven amines (172 frequencies) calculated by MM4 have an overall rms error of 27 cm(-1), compared with corresponding MM4 value of 24 cm(-1) for alkanes. The rms and signed average errors of the moments of inertia of nine simple amines compared with the experimental data were 0.18% and -0.004%, respectively. The heats of formation of 30 amines were also studied. The MM4 weighted standard deviation is 0.41 kcal/mol, compared with experiment. Electronegativity effects occur in the hydrocarbon portion of an amine from the nitrogen, and are accounted for by including electronegativity induced changes in bond lengths and angles, and induced dipole-dipole interactions in the molecule. Negative hyperconjugation results from the presence of the lone pair of electrons on nitrogen, and leads to the Bohlmann bands in the infrared, and also to strong and unusual geometric changes in the molecules (Bohlmann effect), all of which are fairly well accounted for. The conformational energies in amines appear to be less straightforward than those for most other classes of molecules, apparently because of the Bohlmann effect, and these are probably not yet completely understood. In general, the agreement between the MM4 calculated results and the available data is reasonably good.

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“…Structures . Few structural studies (particularly in the gas-phase) have been carried out on the molecules studied herein. − In particular, the experimental information concerning the structures of amides is very scarce. Thus, we have only found gas-phase structural studies for acetamide , (an important neutron diffraction study in condensed phase is given in ref ).…”

Section: Discussionmentioning

confidence: 99%

“…Calculations, notably by Wiberg, Appeloig, Arad, and Rappoport (see also refs and ) on some of these compounds have already been reported, but structural information on the protonated species is much scarcer.…”

Section: Discussionmentioning

confidence: 99%

Strain Effects in Protonated Carbonyl Compounds. An Experimental and ab Initio Treatment of Acyclic Carboxamides and Ketones

et al. 1997

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Strain effects have been quantitatively evaluated for a set of 22 compounds including ketones (R(2)CO), carboxamides (RCONH(2)), and N,N-dimethylcarboxamides (RCONMe(2)), where R = Me, Et, i-Pr, t-Bu, 1-adamantyl (1-Ad), in their neutral and protonated forms. To this end, use was made of the gas-phase proton affinities and standard enthalpies of formation of these compounds in the gas phase, as determined by Fourier transform ion cyclotron resonance mass spectrometry (FT ICR) and thermochemical techniques, respectively. The structures of 1-AdCOMe and (1-Ad)(2)CO were determined by X-ray crystallography. Quantum-mechanical calculations, at levels ranging from AM1 to MP2/6-311+G(d,p)//6-31G(d), were performed on the various neutral and protonated species. Constrained space orbital variation (CSOV) calculations were carried out on selected protonated species to further assess the contributions of the various stabilizing factors. Taking neutral and protonated methyl ketones as references, we constructed isodesmic reactions that provided, seemingly for the first time, quantitative measures of strain in the protonated species. A combination of these data with the results of theoretical calculations (which also included several "computational experiments") lead to a unified, conceptually satisfactory, quantitative description of these effects and their physical link to structural properties of the neutral and protonated species.

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The gas-phase structures of some highly strained compounds: di-t-butylmethane, di-t-butylamine and di-t-butyl ketone

Cited by 13 publications

References 12 publications

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

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

Molecular mechanics (MM4) study of amines

Strain Effects in Protonated Carbonyl Compounds. An Experimental and ab Initio Treatment of Acyclic Carboxamides and Ketones

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