The condensation of trimethylsilylium with water and the proton affinity of trimethylsilanol

Stone, John A.; Wojtyniak, Anastasia C. M.; Wytenburg, Willum

doi:10.1139/v86-092

Cited by 21 publications

(6 citation statements)

References 6 publications

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“…The equilibrium constant was measured at different temperatures; the results are shown in the van't Hoff plot of Figure and the standard enthalpy and entropy changes, obtained from the slope and intercept respectively, are presented in Table . To be noted in Figure is the very low intensity at all times of m / z 91, the (CH 3 ) 3 Si + adduct with adventitious water, which is protonated trimethylsilanol …”

Section: Resultsmentioning

confidence: 98%

Stabilization of Vinyl Cations by β-Silicon: A Quantitative Mass Spectrometric Study

et al. 1996

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The stabilization afforded a vinyl cation by a β-(CH3)3Si substituent has been determined by measuring in a high-pressure mass spectrometer the thermodynamic data for the association of three alkynes (RCCR‘) with (CH3)3Si+ and with the proton. The measured −ΔH° (kcal mol-1) and −ΔS° (in parentheses, cal K-1 mol-1) values for the reaction (CH3)3Si+ + RCCR‘ ⇄ (CH3)3Si·C(R)CR‘+ are as follows: 1-hexyne (R = H, R‘ = n-C4H9) 25.9 ± 1.5 (19.1 ± 0.2), 2-hexyne (R = CH3, R‘ = n-C3H7) 28.8 ± 1.4 (25.5 ± 0.3), and phenylacetylene (R = H, R‘ = C6H5) 28.2 ± 2.8 (16.5 ± 0.4). By comparison the values for 1-hexene which forms an alkyl cation are 38.2 ± 0.5 kcal mol-1 (48.2 ± 0.1 cal K-1 mol-1). The deduced stabilizations (A) for all the substituents (R, R‘ and (CH3)3Si) obtained from the isodesmic reaction (CH3)3Si·C(R)CR‘+ + CH2CH2 → (CH3)3Si·C(R)C(H)R‘ + CH2CH+ are (kcal mol-1) as follows: 1-hexyne 55, 2-hexyne 58, and phenylacetylene 58. The deduced stabilization for the (CH3)3Si+ adduct of 1-hexene relative to the ethyl cation is 60 kcal mol-1. The measured proton affinities are (kcal mol-1) as follows: 1-hexyne 194.5 ± 0.5, 2-hexyne 195.8 ± 0.2, phenylacetylene 198.6 ± 0.2, and 1-hexene 194.0 ± 0.5. The stabilizations (B) due to R and R‘ in the vinyl cations RC(H)CR‘+ produced by protonaton are calculated from the isodesmic reactions RC(H)CR‘+ + CH2CH2 → RC(H)C(H)R‘ + CH2CH+ and are (kcal mol-1) as follows: 1-hexyne 44, 2-hexyne 46, and phenylacetylene 50. The comparable value for the alkyl cation from the protonation of 1-hexene is 34 kcal mol-1. The stabilizations of the vinyl cations RC(H)CR‘+ due to the presence of a β-(CH3)3Si (A − B) are (kcal mol-1) as follows: 1-hexyne 11, 2-hexyne 12, and phenylacetylene 9. For the alkyl cation formed from 1-hexene, the value is 26 kcal mol-1. The stabilization of a vinyl cation by an α-alkyl or α-aryl substituent is subtantially greater than that afforded by the same substituent in an alkyl cation. The total stabilization afforded by both an α-alkyl or α-aryl substituent and a β-(CH3)3Si substituent appears to be approximately the same in both alkyl and vinyl cations and hence the β-silicon effect is considerably smaller for the vinyl cation.

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Section: Resultsmentioning

confidence: 98%

Stabilization of Vinyl Cations by β-Silicon: A Quantitative Mass Spectrometric Study

et al. 1996

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“…It remains unclear which compounds contribute to this signal, because C 7 H 7 + does not correlate with toluene and for trimethylsilanol and diethyl sulfide a differentiation cannot be made. The ion at m/z 91 has been reported to be the result of the association of the (CH 3 ) 3 Si + ion ( m/z 73.047) with water, 106,107 which here was incommensurable and, if present, the small signal overlapped with the water cluster [(H 2 O) 3 ]H 3 O + . In SIFT‐MS measurements using H 3 O + , trimethylsilanol was shown to give the ion at m/z 91.057, and in the presence of water, it converts to (CH 3 ) 2 SiOH.…”

Section: Resultsmentioning

confidence: 89%

Determination of trace compounds and artifacts in nitrogen background measurements by proton transfer reaction time‐of‐flight mass spectrometry under dry and humid conditions

et al. 2021

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A qualitative analysis was applied for the determination of trace compounds at the parts per trillion in volume (ppt v ) level in the mass spectra of nitrogen of different qualities (5.0 and 6.0) under dry and humid conditions. This qualitative analysis enabled the classification and discovery of hundreds of new ions (e.g., [S x ]H + species) and artifacts such as parasitic ions and memory effects and their differentiation from real gas impurities. With this analysis, the humidity dependency of all kind of ions in the mass spectrum was determined. Apart from the inorganic artifacts previously discovered, many new organic ions were assigned as instrumental artifacts and new isobaric interferences could be elucidated. From 1140 peaks found in the mass range m/z 0-800, only 660 could be analyzed due to sufficient intensity, from which 463 corresponded to compounds. The number of peaks in nitrogen proton transfer reaction (PTR) spectra was similarly dominated by nonmetallic oxygenated organic compounds (23.5%) and hydrocarbons (24.1%) Regarding only gas impurities, hydrocarbons were the main compound class (50.2%). The highest contribution to the total ion signal for unfiltered nitrogen under dry and humid conditions was from nonmetallic oxygenated compounds. Under dry conditions, nitrogen-containing compounds exhibit the second highest contribution of 89% and 96% for nitrogen 5.0 and 6.0, respectively, whereas under humid conditions, hydrocarbons become the second dominant group with 69% and 86% for nitrogen 5.0 and 6.0, respectively. With the gathered information, a database can be built as a tool for the elucidation of instrumental and intrinsic gas matrix artifacts in PTR mass spectra and, especially in cases, where dilution with inert gases plays a significant role. K E Y W O R D Sgas impurities, gas traces, industrial gases, proton transfer reaction time-of-flight mass spectrometry, volatile organic compounds

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“…The reaction products are therefore equivalent to those obtained by protonation of the germanols R3GeOH. The absence of appropriate thermodynamic data for such compounds prevents the calculation of their proton affinities from the enthalpies of binding as was done for trimethylsilanol (3) [3] (R3Mf + H20 S R3MOH2+) and [4] (R3MOH2+ + H20 S R3M(OH2)2+) than the addition of the first molecules. The exothermicity is slightly greater for the latter ion than for the former while the entropy change is much more negative for latter.…”

Section: R3geoh2+ Is Further Solvated By Watermentioning

confidence: 99%

“…We have previously reported the enthalpies of binding of (CH3),Si+ to a variety of aromatic and oxygen-containing bases (2,3). The enthalpy values are based on an absolute measurement obtained from the temperature coefficient of the equilibrium constant for reaction [ 11. In this paper we report a similar measurement for the analogous reaction [2] In addition, the ready availability of other germanium tetraalkyl compounds allowed the measurement of the enthalpy of binding of water to other R3Ge+ ions (R = C2H5, n-C3H7, butyl).…”

Section: Introductionmentioning

confidence: 99%

The binding energies of trialkylgermanium cations to water molecules studied by high pressure mass spectrometry

Stone¹,

Wytenburg²

1987

Can. J. Chem.

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Can. J. Chem. 65, 2146 (1987. The binding energies of H20 to R3Ge+ have been measured using pulsed electron beam, high pressure mass spectrometry.van't Hoff plots have yielded thermodynamic data (AH', AS0) for the reactions, [5], R3Ge+ + H70 e R3GeOH2+ (R = CH3, C2Hs, C3H7, C4H9) and [7], R3GeOH2+ + H20 e R3Ge(OH2)2+ (R = CH3, C2HS). AH: decreases with increasing size of R (CH3 28.6 ? 0.5 kcal mol-', C4H9 20.6 + 1.2 kcal mol-I) while AS: shows much less change ( On a mesure les Cnergies de liaison du H20 au R3Ge+ en faisant appel a la spectromktrie de masse a haute pression et a faisceau dlClectrons pulsks. Les courbes de van't Hoff ont permis d'obtenir les donnkes thermodynamiques (AH0 et AS') pour les rkactions R3Ge+ + H20 E R3GeOH2+ (5) (R = CH3, CzH5, C3H7 et C4H9) et R3GeOH2+ + H20 E R3Ge(OH2)' (7) (R = CH3 et C2H5). Le AH! diminue avec une augmentation de la taille du groupement R (CH2, 28,6 + 0,5 kcal mol-', C4H9, 20,6 + 1,2 kcal mol-I) alors que le AS! varie beaucoup moins (34,4 + 0,9 a 30,3 + 2,8 cal K-' mol-'). Une comparaison des donnCes pour (CH3)3M+ (M = Si, Sn) dkmontre que I'knergie de liaison diminue avec une augmentation de la taille de M.[Traduit par la revue]

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The condensation of trimethylsilylium with water and the proton affinity of trimethylsilanol

Cited by 21 publications

References 6 publications

Stabilization of Vinyl Cations by β-Silicon: A Quantitative Mass Spectrometric Study

Stabilization of Vinyl Cations by β-Silicon: A Quantitative Mass Spectrometric Study

Determination of trace compounds and artifacts in nitrogen background measurements by proton transfer reaction time‐of‐flight mass spectrometry under dry and humid conditions

The binding energies of trialkylgermanium cations to water molecules studied by high pressure mass spectrometry

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