Tracer alcohols

A side reaction of this oxygenate initiation is the production of CO2 from the added tracer alcohols. Its C-O-H group gets chemisorbed in the vicinity of an M=0 entity, which obtained its oxygen from the dissociation of CO. CO2 produced from l-[ C]-l-pentanol tracer was radioactive but it was inactive if 2-[ C]-l-hexanol was added. The complicated reaction sequence of FT is still not clarified in every detail. The role of reactor hold-up in determining the distribution of alkanes and alkenes in higher C-number products has been pointed out recently. Possible suggested reaction routes ( current mechanism and futuristic needs ) have been summarised by Davis. 

Sun-Chen examined tracer diffusion data of aromatic solutes in alcohols up to the supercritical range and found their data correlated with average deviations of 5 percent and a maximum deviation of 17 percent for their rather hmited set of data. 

The hetero ring in 4-(l -hydroxyalkylidene)-5-oxazolones is cleaved by alcoholic HCl to form alkyl a-acylaminoacylacetates, which cyclize to oxazole-4-carboxylates [Eq. (25)]. This rearrangement occurs directly in alkali, and a carbon-14 tracer study has substantiated a mechanism involving ring opening followed by the alternative ring closure. ... 

The solid base catalysed aldol condensation of acetone was performed over a CsOH/Si02 catalyst using a H2 carrier gas. The products observed were diacetone alcohol, mesityl oxide, phorone, iso-phorone and the hydrogenated product, methyl isobutyl ketone. Deuterium tracer experiments were performed to gain an insight into the reaction mechanism. A mechanism is proposed. 

The rate of dehydration of the cis diol was about fifty times slower than that of the trans diol and the product of the reaction consisted mainly of cyclohexenol. The 1,4-epoxycyclohexane formed in the reaction was formed after a prior epimerization of the cis to the trans diol this was demonstrated by means of tritium tracer technique. When irons-1,4-cyclohexanediol was dissolved in ieri-butyl alcohol-T having the hydroxyl hydrogen marked with tritium (C4H,OT) the 1,4-epoxycyclohexane produced in this reaction had a very low tritium content. A similar reaction carried out with cis-1,4-cyclohexanediol produced a highly tritiated 1,4-epoxycyclohexane. The insertion of tritium in the 1,4-epoxycyclohexane produced from the cis diol can be explained as follows ... 

Very few direct measurements of the reaction of surface silanol groups on quartz have been reported. This is apparently caused by the small effects due to the limited surface areas available. Adsorption of sodium ions on quartz was measured by radioactive tracer techniques by Gaudin et al. (293). Saturation was achieved at high pH (>10) and sodium ion concentrations above 0.07 Jlf. The calculated packing density of silanol groups was 4.25/100 A. Goates and Anderson (294) titrated quartz with aqueous sodium hydroxide and alcoholic sodium ethylate. The occurrence of two types of acidic groups was reported. 

Butanol and methanol were used in most applications of microemulsions. Ishihama et al. investigated the effect of alcohol on the migration factor of the solute in different systems and on the migration of SDS micelles with or without alcohol. Sudan III migrated as tracer for micelles of SDS faster than dodecylbenzene in the SDS/butanol system (10-12). Due to the addition of butanol to the ME solution, the CMC values decrease very sharply. 

The interpretation of the results of tracer experiments of this sort is sometimes complicated by, sO-exchange reactions. l80 from the solvent may be incorporated into the unreacted ester as hydrolysis proceeds (see below, p. 105), or into either or both of the products. The exchange reaction is significant with alcohols, such as triphenylmethyl alcohol, which give rise to relatively stable carbonium ions under acidic conditions (see, for example, refs. 67, 85), viz-... 

For general purpose tracer work, however, and particularly in polymer chemistry, the liquid scintillation counter surpasses all other instruments in its sensitivity and adaptability. There is no question on the author s mind that at the present time such an instrument would be the first choice, particularly where tritium, carbon-14 or sulphur-35 were involved. Samples for assay are dissolved in a phosphor whose major solvent usually consists of toluene, toluene-alcohol, or dioxan. Many polymers and low molecular weight compounds are readily soluble in these solvents. Prospective users should not be deterred by alleged complications due to "variable quench effects" as these effects are readily corrected for via internal or external standards or the channels ratio method (7, 46, 91). Dilution quench corrections, though valid, are tedious and unnecessary. Where samples are insoluble in phosphor they may be suspended (e.g. as gels or as paper cut from chromatograms, etc.) or they can be burnt and the combustion products absorbed in a suitable phosphor solution. A modification of the Schoniger flask combustion technique is particularly suitable for this purpose (43—45). 

At the Mellon Institute he applied l4C tracers to examine the behavior of intermediates in Fischer-Tropsch synthesis over iron catalysts. By adding small amounts of radioactively labeled compounds to the CO/H2 synthesis gas mixtures, he was able to prove that some of these compounds (e.g., small alcohols) are involved in the initiation step of the chain growth process that leads to larger hydrocarbon products. It was during this era that his associates first placed a catalytic reactor into the carrier gas stream of a gas chromatograph and developed the microcatalytic pulse reactor, which is now a standard piece of equipment for mechanistic studies with labeled molecules. While at Mellon Institute Emmett began editing his comprehensive set of seven volumes called Catalysis, which he continued at Hopkins. 

A tracer technique was employed in an effort to gain further information about the reaction mechanism (10). One alpha hydrogen atom of n-octyl alcohol was replaced with an atom of deuterium. The steps of the two reaction mechanisms under discussion are presented in Fig. 2. If the exchange between hydrogen and deuterium is small, the presence of significant quantities of deuterium in the gaseous product may be explained only by mechanism (1). The exact experimental details of this investigation will now be discussed. 

Amusingly enough, we have managed to devise not one but four more or less acceptable routes, arriving at two hypothetical (Va, Vb) and two real (Villa, Vlllb) structures by quite dissimilar approaches. Mechanistically speaking, this predicament is unacceptable and demands further experimental clarification. Fortunately, labeling experiments have been performed using 0 tracers specifically at the acetate carbonyl of I. After hydrolysis of II the label was found in the alcohol by-product. The only route that accounts for this observation is the sequence B, D of Scheme 48.2. As a consequence, were compound I really optically active (it was not in the actual experiment), only the optically active Vila should have been obtained. Since asymmetric syntheses are an important subject of research nowadays, the real experiment should be run. 

Number of C fCp) and their reactivity in a propagation reaction (propagation rate constant kp). Cp data can be used to determine the mole fraction of active metal centers, the localization of active centers on the surface of the solid catalyst, and the role of individual components of the catalytic system in the formation of active centers. Systematic data on the influence of the catalyst composition and polymerization conditions on Cp and the rate constants of individual steps are important for the determination of the composition of the active centers and the elucidation of the mechanism of these steps. Various methods for determining Cp and kp in catalytic polymerizations of olefins have been reported A direct method for the determination of Cp is the radioactive tracer technique. In this method radioactive compounds react with the AC thus introducing radioactivity into the growing polymer chain. The use of radioactive alcohols is the classical example of this technique... 

Further reports have appeared on the reaction of trivalent phosphorus compounds with acetylene dicarboxylates. In the first, alkyl diphenylphosphinites (e.g.57) are shown to react with dialkylacetylene dicarboxylates (e.g.58) in the presence of carbon dioxide to form 1,2-oxaphosphol-3-enes (e.g.59) which in the presence of excess phosphinite decompose via (60) to give di-ylids (e.g.61). On the other hand, the phosphoranes (62) from phosphonites and phosphites react with a further phosphorus component to give the ylids (63) which are readily converted by treatment with alcohol into phosphonates (65) apparently via ketene intermediates (64) as evidenced by and isotopic tracer studies. ... 

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