O Labeling Study

The indicated reaction mechanism was verified by O-labeling studies. " ... 

Methyl 6-deoxy-j8-D-glucopyranoside 2- and 4-toluene-p-sulphonates have been converted into the expected 2,3- and 3,4-oxirans, respectively, using a basic resin neither oxiran underwent migration under the reaction conditions used. An O-labelling study of the deamination of 2-amino-2-deoxy-D-mannose has shown that at least 62% of the D-glucose formed arises from 1,2-anhydro-D-glucopyranose, whereas the rest results from nucleophilic attack of water at C-2 of the diazonium ion. ... 

The hydration of more inert ions has been studied by O labelling mass spectrometry. 0-emiched water is used, and an equilibrium between the solvent and the hydration around the central ion is first attained, after which the cation is extracted rapidly and analysed. The method essentially reveals the number of oxygen atoms that exchange slowly on the timescale of the extraction, and has been used to establish the existence of the stable [1 10304] cluster in aqueous solution. 

The existence of the OF radical was further estabHshed by use of O-labeled compounds and O nmr studies to verify the mechanism (29) ... 

However, an elegant O nmr study using specifically labelled [CoINHslsl ONO)] " and (Co(NH3)5(ON 0)] established that spontaneous intramolecular O-to-O exchange in the nitrite ligand occurs at a rate comparable to that of the spontaneous O-to-N isomeri /ation/ ° ... 

SUMMARY - Different forms of adsorbed molecular and atomic oxygen on an Ag(UO) surface are analyzed from a theoretical point of view. It is proposed that the active intermediate for the epoxidation of ethylene is an Ag-O surface species. A parallel is made to discrete silver complexes as catalysts for alkene epoxidation as it is experimentally shown that these have similar properties at the silver surface. 180 Labelling studies indicate an Ag-O complex as the reactive catalyst. 

Labelling studies have shown27 that the unusual base-catalysed rearrangement of the P-O-4 lignin model (25) to (27) containing an a-O-4 linkage, proceeds by way of intermediate (26). Acylation of hydroxy aromatic compounds with 2-bromo-2-... 

Fig. 11.36. H202/Na0H oxidation of a trialkylborane (see Figure 3.17 for the preparation of trialkylboranes D and E and for the mechanism of the hydrolysis of the resulting boric acid ester). Deuterium labeling studies show that the conversion of the C-B into the C-O bonds occurs with retention of configuration.

Since 1,3-dioxolanes are cyclic acetals it follows that they are readily hydrolyzed by acids. The kinetics of this hydrolysis have been extensively reviewed (57MI43000). The acidic hydrolysis of 1,3-oxathiolanes is of theoretical importance in that there are conflicting reports as to whether the C—O or the C—S bond is ruptured first. It is known that protonation of 2,2-dimethyl-l,3-oxathiolane in fluorosulfonic acid leads to the exclusive formation of dication (68) (71BSF541). Based on deuterium labelling studies, however, the present data suggest that the C—O bond is broken first in aqueous systems (72TL2569). 

VVe said in. Section 2J.6 that mechanistic studies on ester hydrolysis have been carried out using ethyl propanoate labeled with in the etherlike oxygen. Assume that O-labeled acetic acid is your only source of iso-to[iic oxygen, and then propose a synthesis of the labeled ethyl propanoate. 

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