Oxalic acid labelled with isotopic

When geraniol reacts with phenols in the presence of acid, the common products are usually cyclized the use of 1 % oxalic acid has now been found to minimize cyclization in the reaction between orcinol and geraniol. Nerol has been labelled with deuterium in various positions [a, b, c, and d in (32)] and then converted into the chloride (33). Kinetic isotope effects on hydrolysis of (33) were measured, and 7r-participation in the cationic intermediate (34) leading to the cyclized terpinyl derivatives is discussed. Schwartz and Dunn proposed to use the complex (35), from geranyl methyl ether, as a model for a farnesol cyclization. They were not able to isolate this complex (although there was some evidence for its formation), the main complex (36%) being a dimeric a-complex (36), together with 39 % of the ketone (37), but no cyclized material. The cyclization of the acid chloride (38) to menthone and the C9 hydrocarbon (39) with tributyltin hydride, and also the optimum conditions for the cyclization of (-i-)-citronellal... 

The performance of the FBI can be enhanced by the use of (volatile) additives, such as ammonium acetate, formate, or oxalate, to the mobile phase [92]. They are assumed to act as carriers. Similarly, the use of additives with structures related to the target analyte structures, e.g., phenoxyacetic acid in the analysis of chlorophenoxyacetic acids, was evaluated as well [93]. The carrier effects, exerted by either mobile-phase additives, coeluting compounds, and/or isotopically-labelled standards, is not really understood from a mechanistic point of view. It caimot be applied to consistently enhance the performance for some compounds it works fine, while for others no effects are observed. 

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