Methane protonation

More recently, Usuki etal. studied, using NMR techniques, the conformation of spirocyclic oxaziridines 3 derived from substituted cyclohexanones <1995JOC8028>. Depending on substitution and on the stereochemistry, these compounds exhibit a substantial upfield shift of the cyclohexyl methylene or methane protons with a 1,3-diaxial relationship to the oxaziridine N-substituent. This effect is ascribed to a conformation that places an aromatic group over the plane of the cyclohexane ring. This conformation has also been observed in the solid state by X-ray crystallography and is further supported by molecular mechanics calculations. 

Conditions [rac-LA]yAl] = 100 [rac-LA] = 1.0 M in toluene, 70°C. Determined by the integration ratio of the methane protons in monomer and polymer. The number average molecular weight (MJ and molecular weight distribution (MyM ) were determined by gel permeation chromatograph, calibrated with polystyrene standards in THF, = 0.58. 

CO-RM 24 was also developed further by Schatzschneider and coworkers using some procedures developed by Regal and co-workers. The methane proton in tpm ligand 23 was removed using base to provide an anchor for further synthesis. Scheme 9 shows how CO-RM 25 was synthesised, which can then be easily functionalised by various reactions. 

In Experiment 28A, the yeast reduction of ethyl acetoacetate forms a product that is predominantly the (S)-enantiomer of ethyl 3-hydroxybutanoate. In this part of the experiment, we will use NMR to determine the percentages of each of the enantiomers in the product. The 300 MHz proton NMR spectrum of racemic ethyl 3-hydroxybutanoate is shown in Figure 1. The expansions of fhe individual patterns from Figure 1 are shown in Figure 2. The methyl protons (HJ appear as a doublet at 1.23 ppm, and the methyl protons (H, ) appear as a triplet at 1.28 ppm. The methylene protons (H and H ) are diastereotopic (nonequivalent) and appear at 2.40 and 2.49 ppm (each a doublet of doublefs). The hydroxyl group appears at about 3.1 ppm. The quartet at 4.17 ppm results from the methylene protons (HJ split by the protons (Hjj).The methane proton (H ) is buried under the quartet at about 4.2 ppm. 

Random-walk calculations have been used to explain why, in the oxidation of fatty acids, C-7—C-10 methane protons are oxidized more than others in acetic acid media ... 

In a typical 400 MHz H-NMR spectra of low-conversion S-AA bulk copolymer dissolved in deuterated dimethyl sulfoxide (DMSO-Dg) and in DMSO-Dg-CDCl3 at 50 °C, the chemical shift of different protons, respectively, are 1-2 ppm for all methane protons and the methylene proton of the styrene emits in the copolymer chain 2.3 ppm for the methylene proton of the acrylic acid emit in the copolymer chain 3.3 ppm for water in DMSO-Dg, 5.2-6.4 ppm multi-peaks for the end groups of the copolymer chains that may be double bonds and isobntylnitrile 6.4-7.4 ppm for aromatic protons and 12.1 for the proton of the carboxyl gronp on the copolymer chain. 

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