Thermochemistry of organosilicon compounds

Воронков, М. Г.; Klyuchnikov, V.A.; Mironenko, E.V. Mironenko; Shvets, G.N.; Danilova, T. F.; Khudobin, Yu. I.

doi:10.1016/0022-328x(91)83174-3

Cited by 22 publications

(7 citation statements)

References 10 publications

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“…Cyclosiloxanes are considered to be less strained than cyclic ethers and acetals of the same ring size because of the greater flexibility of the SiOSi linkage. Thus, the values reported in ref c seem to be too high.…”

Section: Resultsmentioning

confidence: 82%

“…However, the strain in permethylcyclosiloxanes is subject to some controversy. For example, according to calorimetric measurements of equilibration reactions (i.e catalytic decomposition of the starting siloxane leading to the thermodynamic mixture of cyclic and open chain polysiloxanes), 3a,b the strain energy of the D 3 ring is about 2−4 kcal/mol and D 4 is practically strainless (0.25 kcal/mol). 25a,b In contrast, combustion enthalpy measurements gave strain energies of 19 kcal/mol for D 3 and 14 kcal/mol for D 4 25c. The latter values are, however, inconsistent with the thermodynamic data for the polymerization of cyclosiloxanes 3 and with the data for other heterocyclic monomers .…”

Section: Resultsmentioning

confidence: 99%

“…The most appropriate reaction to compute the strain energy of 5a seems to be the conversion of cyclotrisiloxane into a larger unstrained ring like cyclotetrasiloxane (eq 4) 25b. The energy released in this reaction (for 4 mol of 5a ) is 19.7 kcal (4.9 kcal/mol, 1.6 kcal per SiO bond) at MP4/6-31G*//HF/6-31G* and 26.4 kcal at HF/6-31G* (74.2 kcal, 17.7 kcal/mol at 3-21G 17a ).…”

Section: Resultsmentioning

confidence: 99%

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Ab Initio Study of Silyloxonium Ions

Cypryk

Apeloig

1997

Organometallics

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The geometries and proton and silylenium cation (H3Si+) affinities as well as ring strain energies of several hydrogen-substituted cyclic siloxanes, cyclotrisiloxane (H2SiO)3 (5a), cyclotetrasiloxane (H2SiO)4 (6a), and 1,3-oxadisilacyclopentane (7a), were calculated by ab initio quantum-mechanical methods using the polarized 6-31* basis set. Protonation and silylenium cation addition to siloxanes lead to secondary and tertiary silyloxonium ions, respectively. The calculated strain energies follow the order: 7a > 5a > 6a ≈ 0. Upon protonation or silylation, the strain in the five-membered ring of 7b and 7c is significantly reduced, while in the cyclotrisiloxane silyloxonium ions 5b,c the strain is preserved. The endocyclic Si−O bonds in 7a and 5a are weakened upon protonation or addition of H3Si+ more than the exocyclic bonds and are therefore predicted to be cleaved more readily by nucleophiles, resulting in a ring opening rather than in splitting of the exocyclic SiH3 group. 7a is by ca. 10 kcal/mol more basic than the other siloxanes due to the angular strain in the five-membered ring. Its basicity is comparable to that of dialkyl ethers and alkoxysilanes. A linear correlation was found between the gas-phase proton and H3Si+ affinities. On the basis of SCRF calculations interaction with solvent (cyclohexane or CH2Cl2) has only a moderate effect on the energies of protonation and ring-opening reactions. The role of silyloxonium ions as possible active centers in the cationic ring-opening polymerization of cyclosiloxanes is discussed in light of the calculated basicities and ring strain energies. The calculations suggest that the polymerizations of the cyclic monomers 5a, 6a, and 7a should reveal different kinetic and thermodynamic behavior. 7a is predicted to be the most reactive monomer, and its polymerization is the most favored thermodynamically.

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Section: Resultsmentioning

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Ab Initio Study of Silyloxonium Ions

Cypryk

Apeloig

1997

Organometallics

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“…The first fragment has been determined on the base of the formation enthalpies of over fifty peroxides, the second one was determined on the base of five compounds with a triple bound. The value of C-(Si)(H) 3 fragment (kJ×mol -1 ) can be found in the following articles: [21] 44.27; [22][23][24] 40.27; [25] 42.17. All the fragments of organosilicon compounds have been recalculated [21][22][23][24].…”

Section: Resultsmentioning

confidence: 99%

Thermodynamic properties of silicon containing acetylene peroxides

Dibrivny¹,

Van-Chin-Syan²,

Melnyk³

2008

ChChT

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A technique for the explosion combustion of liquid organosilicon peroxides has been developed. Five Silicon containing acetylene peroxides have been investigated thermodynamically. Their combustion and evaporation enthalpies have been determined. Formation enthalpies of the compounds concerned in the condensed and gaseous states have been calculated. The magnitudes of two fragments for Benson additive scheme of formation enthalpies have been determined.

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“…We know of no measurements of the enthalpy or the Gibbs energy of formation or of polymerization of any silacyclohexane. However, should we generalize this concern to include general silicon-containing 6-membered ring heterocycles, we note the measurements on hexasubstituted cyclotrisiloxanes [34,35] and those on solid silicon carbide.…”

Section: Issuementioning

confidence: 99%

Interplay of thermochemistry and structural chemistry, the journal (volume 24, 2013, issues 3–4) and the discipline

et al. 2014

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The contents of issues 3 and 4 for the calendar year 2013 are summarized in the current review of the journal Structural Chemistry. A brief thermochemical commentary is added to the summary of each paper. Abbreviations AIM Atoms in molecules BNNT Boron nitride nanotube CNC Carbon nanocone CSD Crystal structure determination DFT Density functional theory DNB 1,5-Dinitrobiuret EDA Energy decomposition analysis HF Hartree-Fock GED Gas electron diffraction GIAO Gauge-independent atomic orbital HOMA Harmonic oscillator measure of aromaticity MD Molecular dynamics MP Møller-Plesset perturbation MP2Second-order Møller-Plesset perturbation NRT Natural resonance theory ONIOM Our own N-layered integrated molecular orbital and molecular mechanics QTAIM Quantum theory of atoms-in-molecules NAO Natural atomic orbital NBO Natural bond orbital PES Potential energy surface

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Thermochemistry of organosilicon compounds

Cited by 22 publications

References 10 publications

Ab Initio Study of Silyloxonium Ions

Ab Initio Study of Silyloxonium Ions

Thermodynamic properties of silicon containing acetylene peroxides

Interplay of thermochemistry and structural chemistry, the journal (volume 24, 2013, issues 3–4) and the discipline

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