Posts Tagged ‘Conformational isomerism’
Saturday, September 1st, 2018
I am exploring the fascinating diverse facets of a recently published laboratory experiment for undergraduate students.[1] Previously I looked at a possible mechanistic route for the reaction between an enal (a conjugated aldehyde-alkene) and benzyl chloride catalysed by base and a chiral amine, followed by the use of NMR coupling constants to assign relative stereochemistries. Here I take a look at some chiroptical techniques which can be used to assign absolute stereochemistries (configurations).
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References
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M. Meazza, A. Kowalczuk, S. Watkins, S. Holland, T.A. Logothetis, and R. Rios, "Organocatalytic Cyclopropanation of (E)-Dec-2-enal: Synthesis, Spectral Analysis and Mechanistic Understanding", Journal of Chemical Education, vol. 95, pp. 1832-1839, 2018. http://dx.doi.org/10.1021/acs.jchemed.7b00566
Tags:Absolute configuration, Biochemistry, bulk solutions, chemical transformations, Chemistry, Conformational isomerism, difficult energy difference, gas phase, higher energy forms, Interesting chemistry, Isomer, Isomerism, Nature, Physical organic chemistry, Polarization, spectroscopy, stereochemical product, Stereochemistry, Stereoisomerism, Vibrational circular dichroism
Posted in Uncategorised | No Comments »
Thursday, June 1st, 2017
Conformational polymorphism occurs when a compound crystallises in two polymorphs differing only in the relative orientations of flexible groups (e.g. Ritonavir).[1] At the Beilstein conference, Ian Bruno mentioned another type; tautomeric polymorphism, where a compound can crystallise in two forms differing in the position of acidic protons. Here I explore three such examples.
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References
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G.J.O. Beran, I.J. Sugden, C. Greenwell, D.H. Bowskill, C.C. Pantelides, and C.S. Adjiman, "How many more polymorphs of ROY remain undiscovered", Chemical Science, vol. 13, pp. 1288-1297, 2022. http://dx.doi.org/10.1039/D1SC06074K
Tags:Chemical IT, Chemistry, chloroform solutions, Conformational isomerism, Crystal, crystallography, gas phase, Ian Bruno, Isomerism, Polymorphism, Ritonavir, S-centre, Tautomer
Posted in crystal_structure_mining | No Comments »
Thursday, April 6th, 2017
Enols are simple compounds with an OH group as a substituent on a C=C double bond and with a very distinct conformational preference for the OH group. Here I take a look at this preference as revealed by crystal structures, with the theoretical explanation.
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Tags:Chemical bond, chemical bonding, Chemistry, Conformational isomerism, constrained search, Enol, free energy, Gauche effect, Hydrogen bond, Isomerism, Java, Physical organic chemistry, search query, Stereochemistry, Supramolecular chemistry
Posted in crystal_structure_mining, reaction mechanism | 2 Comments »