scholarly journals Oxatriquinane Derivatives: A Theoretical Investigation of SN1-SN2 Reactions Borderline

2016 ◽  
Vol 15 (6) ◽  
pp. 439-453
Author(s):  
Olaide WAHAB ◽  
Jide IGE ◽  
Grace OGUNLUSI ◽  
Lukman OLASUNKANMI ◽  
Kayode SANUSI
Keyword(s):  
Transition State ◽  
Nucleophilic Substitution ◽  
Reaction Mechanisms ◽  
Geometry Optimization ◽  
Geometrical Isomer ◽  
Sn2 Reactions ◽  
Azide Ion ◽  
Paper Plane ◽  
Sn2 Pathway

This study investigated the nucleophilic substitution reaction mechanisms of 5 oxatriquinane derivatives, namely: oxatriquinane (OTQ), 1,4,7-trimethyloxatriquinane (TMO), 1,4,7-triethyloxatriquinane (TEO), 1,4,7-tri-iso-propyloxatriquinane (TIO) and 1,4,7-tri-tert-butyloxatriquinane (TTO). In addition to the G3 conformation (one with the substituent groups at 1,4 and 7 positions pointing into the plane of the paper) originally proposed by the previous workers, Mascal et al. in 2008 and Gunbas et al. in 2013, one more geometrical isomer was considered again for each of the derivatives, the 2G1 isomer (one in which only 2 of the 3 substituent groups at 1,4 and 7 positions are into the paper plane). Geometry optimization and determination of transition state properties of the conformers corresponding to each molecule (in the presence of azide ion, N3-) provided theoretical evidences on the possible reaction mechanisms. The 2G1 conformer for TTO was found to be unstable. The reactions of OTQ, TMO and TEO with azide ion (N3-) followed SN2 pathway, with SN1mechanism completely lacking. This finding is in agreement with the first set of reports published on this subject in 2008 and 2010 by Mascal’s group. For TIO (in the presence of azide ion), only the presence of SN1 mechanism could be proved without any observation of transition state (TS), even though, it possesses a 2G1 conformer. TTO surprisingly, showed marked evidence of SN1 mechanism also without any evidence of TS. The results obtained showed that OTQ derivatives up to TEO undergo nucleophilic substitution predominantly via SN2, and above which (i.e. for TIO and TTO) the mechanisms predominantly become SN1.

Determination of Complex Reaction Mechanisms

2006 ◽  
Author(s):  
John Ross ◽  
Igor Schreiber ◽  
Marcel O. Vlad
Keyword(s):  
Reaction Mechanism ◽  
Reaction Mechanisms ◽  
Reaction Pathway ◽  
Chemical Species ◽  
Rate Coefficients ◽  
Chemical System ◽  
Evolutionary Development ◽  
Complex Reaction ◽  
Oscillatory Reactions

In a chemical system with many chemical species several questions can be asked: what species react with other species: in what temporal order: and with what results? These questions have been asked for over one hundred years about simple and complex chemical systems, and the answers constitute the macroscopic reaction mechanism. In Determination of Complex Reaction Mechanisms authors John Ross, Igor Schreiber, and Marcel Vlad present several systematic approaches for obtaining information on the causal connectivity of chemical species, on correlations of chemical species, on the reaction pathway, and on the reaction mechanism. Basic pulse theory is demonstrated and tested in an experiment on glycolysis. In a second approach, measurements on time series of concentrations are used to construct correlation functions and a theory is developed which shows that from these functions information may be inferred on the reaction pathway, the reaction mechanism, and the centers of control in that mechanism. A third approach is based on application of genetic algorithm methods to the study of the evolutionary development of a reaction mechanism, to the attainment given goals in a mechanism, and to the determination of a reaction mechanism and rate coefficients by comparison with experiment. Responses of non-linear systems to pulses or other perturbations are analyzed, and mechanisms of oscillatory reactions are presented in detail. The concluding chapters give an introduction to bioinformatics and statistical methods for determining reaction mechanisms.

Determination of heterogeneous reaction mechanisms: A key milestone in dust explosion modelling

2021 ◽  
pp. 104589
Author(s):  
Matteo Pietraccini ◽  
Eloise Delon ◽  
Audrey Santandrea ◽  
Stéphanie Pacault ◽  
Pierre-Alexandre Glaude ◽  
...  
Keyword(s):  
Reaction Mechanisms ◽  
Heterogeneous Reaction ◽  
Dust Explosion

Mechanisms of aromatic nucleophilic substitution by the ambident thiocyanate ion

1973 ◽  
Vol 26 (2) ◽  
pp. 273 ◽  
Author(s):  
DE Giles ◽  
AJ Parker
Keyword(s):  
Nucleophilic Substitution ◽  
Transition States ◽  
Reactivity Ratio ◽  
Substitution Reactions ◽  
Aromatic Nucleophilic Substitution ◽  
Thiocyanate Ion ◽  
Sn2 Reactions ◽  
Leaving Group ◽  
Electrophilic Reactivity ◽  
Saturated Carbon Atom

Sulphur/nitrogen reactivity ratios in a series of aromatic nucleophilic substitution reactions of ambident thiocyanate ion have been determined. There are profound differences from the pattern found in SN2 reactions at a saturated carbon atom. Abnormal transition states, involving interactions between entering and leaving group, are likely in the bond-breaking step of the intermediate complex in reactions of thiocyanate ion with 1-fluoro-2,4-dinitrobenzene and with 2,4- dinitrophenyl 4-toluenesulphonate. The nitro-substituted aryl thiocyanates are shown to be tri-functional electrophiles, with reactive centres at aromatic carbon, at cyanide carbon, and at sulphur. Aryl 4-toluenesulphonates are bifunctional electrophiles with reactive centres at aryl carbon and sulphonyl sulphur. The site of attack by nucleophiles depends on the nature of the nucleophile. The sulphur/nitrogen reactivity ratio of ambident SCN-, and the electrophilic reactivity of tri- and bi-functional substrates, are in most instances consistent with the Hard and Soft Acids and Bases principle. Exceptions to the principle in some instances reveal differences between the SNAr and SN2 mechanisms, and in others indicate abnormal transition states.

scholarly journals Reply to the Comment on “On the SN2 Reactions Modified in Vibrational Strong Coupling Experiments: Reaction Mechanisms and Vibrational Mode Assignments”

2021 ◽  
Author(s):  
Clàudia Climent ◽  
Johannes Feist
Keyword(s):  
Strong Coupling ◽  
Reaction Mechanisms ◽  
Vibrational Mode ◽  
Chem Phys ◽  
Sn2 Reactions ◽  
Original Manuscript ◽  
Supplementary Material ◽  
Phys Chem Chem Phys

<div> <div> <div> <p> </p><div> <div> <div> <p>In September 2020, we became aware that a comment (A. Thomas, L. Lethuillier-Karl, J. Moran and T. Ebbesen, 2020, DOI:10.26434/chemrxiv.12982358.v1.) on our recent paper (C. Climent and J. Feist, Phys. Chem. Chem. Phys., 2020, 22, 23545) had been posted to ChemRxiv. Since our attempts in October 2020 to reach out to the authors to discuss the points they raised did not receive a response as of April 2021, and the comment was not submitted as a formal comment to the original journal either, we here provide a brief reply based on the results that were already reported in our original manuscript. Most importantly, we show that we did not “presumably overlook” any data in the supplementary material of their original article, but that our results are actually fully consistent with those data. </p> </div> </div> </div> </div> </div> </div>

Sign in / Sign up

Export Citation Format

Share Document