Posts Tagged ‘Electrophile’
Tuesday, June 21st, 2016
Tags:Asymmetric hydrogenation, benzene, benzo, Electrophile, Furan, Indole, Pyridine, Pyrrole, search query, Simple aromatic rings, Substitution reaction, Thiophene
Posted in crystal_structure_mining | No Comments »
Wednesday, May 11th, 2016
I have previously commented on the Bürgi–Dunitz angle, this being the preferred approach trajectory of a nucleophile towards the electrophilic carbon of a carbonyl group. Some special types of nucleophile such as hydrazines (R2N-NR2) are supposed to have enhanced reactivity[1] due to what might be described as buttressing of adjacent lone pairs. Here I focus in on how this might manifest by performing searches of the Cambridge structural database for intermolecular (non-bonded) interactions between X-Y nucleophiles (X,Y= N,O,S) and carbonyl compounds OC(NM)2.
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References
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G. Klopman, K. Tsuda, J. Louis, and R. Davis, "Supernucleophiles—I", Tetrahedron, vol. 26, pp. 4549-4554, 1970. http://dx.doi.org/10.1016/S0040-4020(01)93101-1
Tags:Bases, Bürgi–Dunitz angle, Carbonyl, Chemical IT, Electrophile, Ester, Flippin–Lodge angle, Functional groups, hydrazine, non-metal attachments, Nucleophile, Physical organic chemistry, search query, Superbase
Posted in crystal_structure_mining | 1 Comment »
Thursday, January 7th, 2016
This is the third and final study deriving from my Ph.D.[1]. The first two topics dealt with the mechanism of heteroaromatic electrophilic attack using either a diazonium cation or a proton as electrophile, followed by either proton abstraction or carbon dioxide loss from the resulting Wheland intermediate. This final study inverts this sequence by starting with the proton abstraction from an indolinone by a base to create/aromatize to a indole-2-enolate intermediate, which only then is followed by electrophilic attack (by iodine). Here I explore what light quantum chemical modelling might cast on the mechanism.
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References
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B.C. Challis, and H.S. Rzepa, "Heteroaromatic hydrogen exchange reactions. Part VIII. The ionisation of 1,3-dimethylindolin-2-one", Journal of the Chemical Society, Perkin Transactions 2, pp. 1822, 1975. http://dx.doi.org/10.1039/P29750001822
Tags:Arenium ion, Bases, diazo, Diazonium compound, Electrophile, Electrophilic aromatic substitution, Equilibrium chemistry, Fortran, Historical, Indole, light quantum chemical modelling, Metal ions in aqueous solution, Nuclear physics, Simple aromatic rings, Solutions
Posted in reaction mechanism | No Comments »
Friday, April 17th, 2015
The knowledge that substituents on a benzene ring direct an electrophile engaged in a ring substitution reaction according to whether they withdraw or donate electrons is very old.[1] Introductory organic chemistry tells us that electron donating substituents promote the ortho and para positions over the meta. Here I try to recover some of this information by searching crystal structures.
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References
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H.E. Armstrong, "XXVIII.—An explanation of the laws which govern substitution in the case of benzenoid compounds", J. Chem. Soc., Trans., vol. 51, pp. 258-268, 1887. http://dx.doi.org/10.1039/CT8875100258
Tags:above search, Aromatic compounds, aromaticity, Birch reduction, Chemical IT, Chemistry, electron donating, Electrophile, Electrophilic aromatic substitution, Ether, Functional groups, little search, Organic chemistry, Physical organic chemistry, Substitution reactions
Posted in crystal_structure_mining | 1 Comment »