Towards understanding solvation effects on the conformational entropy of non-rigid molecules

Gorges, Johannes; Grimme, Stefan; Hansen, Andreas; Pracht, Philipp

doi:10.1039/d1cp05805c

Cited by 23 publications

(25 citation statements)

References 72 publications

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“…While TBDPS favors the more crowded 1,6-COT, the di-OTTMSS substitution pattern prefers the “unfolded” 1,4-COT by Δ r G 313 = +0.13 ± 0.01 kcal mol –1 . While the −CH 2 O– spacer reduces internal strain, entropic contributions significantly dampen the effects of attractive NCIs; the conformational entropy penalty due to the spacer group amounts to Δ S conf ≈ +1.1 kcal mol –1 at 40 °C computed according to Grimme and co-workers. , Still, such small Δ r G 313 values are quite relevant for transition structures, where even small effects lead to large changes in rates and/or selectivities.…”

Section: Resultsmentioning

confidence: 99%

Silyl Groups Are Strong Dispersion Energy Donors

et al. 2022

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We present an experimental and computational study to investigate noncovalent interactions between silyl groups that are often employed as “innocent” protecting groups. We chose an extended cyclooctatetraene (COT)-based molecular balance comprising unfolded (1,4-disubstituted) and folded (1,6-disubstituted) valance bond isomers that typically display remote and close silyl group contacts, respectively. The thermodynamic equilibria were determined using nuclear magnetic resonance measurements. Additionally, we utilized Boltzmann weighted symmetry-adapted perturbation theory (SAPT) at the sSAPT0/aug-cc-pVDZ level of theory to dissect and quantify noncovalent interactions. Apart from the extremely bulky tris(trimethylsilyl)silyl “supersilyl” group, there is a preference for the folded 1,6-COT valence isomer, with London dispersion interactions being the main stabilizing factor. This makes silyl groups excellent dispersion energy donors, a finding that needs to be taken into account in synthesis planning.

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Section: Resultsmentioning

confidence: 99%

Silyl Groups Are Strong Dispersion Energy Donors

et al. 2022

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“…Of course, for many reactions of interest, these molecules are surrounded by solvent molecules. The pitfalls associated with modeling contributions to entropy from solvation have been discussed elsewhere, and Plata and Singleton’s discussion of these issues in the context of modeling a typical organic reaction provides an excellent jumping-off point for interested parties …”

Section: Disorderly Conductmentioning

confidence: 94%

Portable Models for Entropy Effects on Kinetic Selectivity

Tantillo

2022

J. Am. Chem. Soc.

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Differences in entropies of competing transition states can direct kinetic selectivity. Understanding and modeling such entropy differences at the molecular level is complicated by the fact that entropy is statistical in nature; i.e., it depends on multiple vibrational states of transition structures, the existence of multiple dynamically accessible pathways past these transition structures, and contributions from multiple transition structures differing in conformation/configuration. The difficulties associated with modeling each of these contributors are discussed here, along with possible solutions, all with an eye toward the development of portable qualitative models of use to experimentalists aiming to design reactions that make use of entropy to control kinetic selectivity.

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Section: Theorymentioning

confidence: 99%

“…Furthermore, the computational costs for the systems' size in the HS13L for the conformational entropy become unfeasible for larger systems (above 100 atoms) even when using forcefield methods in combination with implicit solvation models. 36 We calculate the solvation free energy with the continuum solvation models COSMO-RS 37,38 and SMD. 39 The alternative explicit consideration of solvent molecules, e.g., in our recent so-called quantum cluster growth (QCG) model 40 would be too computationally too demanding for this system size.…”

Section: Theorymentioning

confidence: 99%