Understanding chemistry with thesymmetry‐decomposed Voronoideformation density charge analysis

Journal of Computational Chemistry, Journal Year: 2023, Volume and Issue: 44(27), P. 2108 - 2119

Published: July 5, 2023

Abstract The symmetry‐decomposed Voronoi deformation density (VDD) charge analysis is an insightful and robust computational tool to aid the understanding of chemical bonding throughout all fields chemistry. This method quantifies atomic flow associated with chemical‐bond formation enables decomposition this into contributions (1) orbital interaction types, that is, Pauli repulsive or interactions; (2) per irreducible representation (irrep) any point‐group symmetry interacting closed‐shell molecular fragments; now also (3) open‐shell (i.e., radical) fragments. VDD augments energy (EDA) so repulsion interactions can be quantified both atom irrep, for example, σ, π, δ electrons. provides detailed insights fundamental aspects are not accessible from EDA.

Language: Английский

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How Solvation Influences the S_N2 versus E2 Competition

The Journal of Organic Chemistry, Journal Year: 2021, Volume and Issue: 87(3), P. 1805 - 1813

Published: Dec. 21, 2021

We have quantum chemically investigated how solvation influences the competition between SN2 and E2 pathways of model F– + C2H5Cl reaction. The system is solvated in a stepwise manner by going from gas phase, then via microsolvation one to three explicit solvent molecules, last bulk using relativistic density functional theory at (COSMO)-ZORA-OLYP/QZ4P. explain why mechanistic pathway shifts phase upon strong Lewis base (i.e., nucleophile/protophile). preferred under weak dichloromethane, whereas switch reactivity observed water. Our activation strain Kohn–Sham molecular orbital analyses reveal that has significant impact on strength base. show furnishes weaker unable overcome high characteristic distortivity associated with pathway, thus becomes viable.

Language: Английский

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Origin of asynchronicity in Diels–Alder reactions

Physical Chemistry Chemical Physics, Journal Year: 2021, Volume and Issue: 23(36), P. 20095 - 20106

Published: Jan. 1, 2021

Quantum chemical activation strain analyses reveal that asynchronicity in Diels–Alder reactions reduces both destabilizing Pauli repulsion as well stabilizing orbital interactions, and occurs if the former dominates.

Language: Английский

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S_N2 versus S_N2′ Competition

The Journal of Organic Chemistry, Journal Year: 2022, Volume and Issue: 87(14), P. 8892 - 8901

Published: June 24, 2022

We have quantum chemically explored the competition between SN2 and SN2′ pathways for X– + H2C═CHCH2Y (X, Y = F, Cl, Br, I) using a combined relativistic density functional theory coupled-cluster approach. Bimolecular nucleophilic substitution reactions at allylic systems, i.e., Cγ═Cβ–Cα–Y, bearing leaving-group α-position, proceed either via direct attack α-carbon (SN2) or an γ-carbon, involving concerted rearrangement (SN2′), in both cases leading to expulsion of leaving-group. Herein, we provide physically sound model rationalize under which circumstances nucleophile will follow aliphatic pathway. Our activation strain analyses expose underlying physical factors that steer SN2/SN2′ and, again, demonstrate concepts reaction's "characteristic distortivity" "transition state acidity" explanations design tools understanding predicting reactivity trends organic synthesis.

Language: Английский

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Backside versus Frontside SN2 Reactions of Alkyl Triflates and Alcohols

Chemistry - A European Journal, Journal Year: 2024, Volume and Issue: 30(25)

Published: Feb. 22, 2024

Nucleophilic substitution reactions are elementary in organic chemistry that used many synthetic routes. By quantum chemical methods, we have investigated the intrinsic competition between backside S

Language: Английский

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C−X Bond Activation by Palladium: Steric Shielding versus Steric Attraction

Chemistry - A European Journal, Journal Year: 2022, Volume and Issue: 28(44)

Published: April 14, 2022

The C-X bond activation (X = H, C) of a series substituted C(n°)-H and C(n°)-C(m°) bonds with C(n°) C(m°) H

Language: Английский

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Nature of C−I⋅⋅⋅π Halogen Bonding and its Role in Organocatalysis

European Journal of Organic Chemistry, Journal Year: 2021, Volume and Issue: 2021(45), P. 6102 - 6110

Published: Nov. 11, 2021

Abstract The nature of the C−I⋅⋅⋅π halogen bonding and its mode activation in organocatalysis have been quantitatively explored detail by means Density Functional Theory (DFT) calculations. To this end, uncatalyzed homo‐[4+2]‐cycloaddition reaction involving 2‐alkenylindoles is compared to analogous process mediated iodine‐substituted azolium salts. It found that catalysts establish relatively strong noncovalent interactions with indole reactant, which are characterized a high degree covalency. This interaction results significant acceleration cycloaddition lowering barrier up 6 kcal/mol respect reaction. calculations predict can be further reduced increasing electrophilicity catalyst. Our quantitative analyses reveal origin catalysis mainly reduction steric (Pauli) repulsion between diene dienophile, therefore confirming generality recently introduced Pauli‐repulsion concept.

Language: Английский

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C(spⁿ)−X (n=1–3) Bond Activation by Palladium

Chemistry - A European Journal, Journal Year: 2021, Volume and Issue: 28(26)

Published: Dec. 27, 2021

We have studied the palladium-mediated activation of C(sp

Language: Английский

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Rational Tuning of the Reactivity of Three‐Membered Heterocycle Ring Openings via S_N2 Reactions

Chemistry - A European Journal, Journal Year: 2022, Volume and Issue: 28(60)

Published: July 28, 2022

Abstract The development of small‐molecule covalent inhibitors and probes continuously pushes the rapidly evolving field chemical biology forward. A key element in these molecular tool compounds is “electrophilic trap” that allows a linkage with target enzyme. reactivity this entity needs to be well balanced effectively trap desired enzyme, while not being attacked by off‐target nucleophiles. Here we investigate intrinsic substrates containing class widely used electrophilic traps, three‐membered heterocycles nitrogen (aziridine), phosphorus (phosphirane), oxygen (epoxide) or sulfur atom (thiirane) as heteroatom. Using quantum approaches, studied conformational flexibility nucleophilic ring opening series model substrates, which traps are mounted on cyclohexene scaffold (C 6 H 10 Y Y=NH, PH, O, S). It was revealed activation energy does necessarily follow trend expected from C−Y leaving‐group bond strength, but steeply decreases S. We illustrate HOMO Nu –LUMO Substrate interaction an all‐important factor for observed reactivity. In addition, show aziridines phosphiranes can tuned far below corresponding epoxides thiiranes addition proper electron‐withdrawing substituents. Our results provide mechanistic insights rationally tune popular guide experimental design enzymatic activity.

Language: Английский

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Origin of Stereoselectivity in S_E2′ Reactions of Six‐membered Ring Oxocarbenium Ions

Chemistry - A European Journal, Journal Year: 2022, Volume and Issue: 29(14)

Published: Dec. 13, 2022

Oxocarbenium ions are key reactive intermediates in organic chemistry. To generate a series of structure-reactivity-stereoselectivity principles for these species, we herein investigated the bimolecular electrophilic substitution reactions (SE 2') between allyltrimethylsilane and archetypal six-membered ring oxocarbenium using combined density functional theory (DFT) coupled-cluster approach. These preferentially proceed following reaction path where ion transforms from half chair (3 H4 or 4 H3 ) to conformation. The introduction alkoxy substituents on ions, dramatically influences conformational preference canonical 3 conformers, thereby stereochemical outcome SE 2' reaction. In general, find that stereoselectivity correlates "intrinsic preference" cations, as dictated by their shape. However, C5-CH2 OMe substituent, steric factors override preference", showing more selective than expected based shape ion. Our energetics correlate well with experimentally observed stereoselectivity, use activation strain model has enabled us quantify important interactions structural features occur transition state precisely understand relative energy barriers diastereotopic addition reactions. fundamental mechanistic insight provided this study will aid understanding reactivity complex glycosyl cations featuring multiple facilitate our general glycosylation

Language: Английский

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