Ammonium salts, labelled

The ethyl cyanoacetate and methyl ethyl ketone were Eastman Kodak Company white label grade chemicals and were used without further purification. Commercial absolute ethanol was found to give a slightly better yield of the ammonium salt of the imide. 

The synthesis and uses of isotopically labelled amino and quaternary ammonium salts... 

Studenov and Beriidge introduced a series of potential F-labeled extractable MBF tracers in the year 2001 that were accessible via reliable 1-2-step radiosynthesis sequences. Five F-labeled amines and four quaternary ammonium salts were obtained by nucleophilic substitution either at aliphatic precursors or at aromatic compounds [71]. Figure 10 summarizes the synthesis of mentioned compounds. 

Fig. 10. Radiosyntheses of F-labeled amines and quaternary ammonium salts as potential MBF tracers [71] (EOS end of synthesis).

Nitrogen NMR data have been obtained using both the low-abundance, spin = 1/2 N and the predominant spin = 1 N nuclei. Several different references have been used for nitrogen NMR including aqueous ammonia, ammonium salts, acetonitrile, nitric acid, and nitrates. Current opinion favors neat nitromethane, and the compilation of the known data for 1,4-oxazines (Table 6) is expressed with respect to this reference and arranged in order of the observed chemical shift. For the C-labeled compound 87, carbamate rotamers lead to two separate signals and the value of 7c n can be determined -283.98 (d, J 9) and -284.46 (d, 7 11) <2001JOC8010>. 

Kummer [19], Friedman and Biegeleisen [20] studied the decomposition of ammonium nitrate labelled withI5N [15N]H4 [14N]03. The completely anhydrous salt did not decompose until 300°C. Only sublimation took place. But a trace of water initiated decomposition at 180°C. The main products of the reaction were NzO and water (according to the eqn. (4)) and with the labelled salt, nitrous oxide [14N] [15N]0 was produced showing that the gas was formed by the interaction of the two ions in the molecule. They also showed that with ordinary ammonium nitrate and H2180, no N2I80 was formed, indicating that the water had a purely catalytic effect. 

A portion of the wet sol-intercalated clay was mixed with a surfactant of quaternary ammonium salts [CH3(CH2)n-i N(CH3)3Br] by stirring for 2 hours. 15.75 mmol of surfactant was added to each gram of the starting bentonite clay. The resultant mixture of clay and surfactant was transferred into an autoclave and kept in an oven at 100°C for 3 days. The wet cake was washed with water to Cl ions free and the solid was recovered by filtration. The solid was dried in room temperature and calcined at 773 K. for 4 h. The calcined products were labeled as sol-PILB-Cn, where n denotes the number of carbon atoms in the alkyl chain of the surfactants used. Four samples were prepared sol-PILB-C12, -C14, -C16 and -C18. 

J. Haberman T.C. Castorina, The Surface Chemistry of HMX , PATR 3089 (1963) [A study was made of the solution-adsorption properties of HMX using a 14C labeled quarternary ammonium salt, stearyl tri-methyl ammonium bromide (STAB). The solvent system used consisted of 10% ethanol and 90% w. The solution-adsorption system isotherms for 10-micron HMX were measured. The authors conclude that an H-type Langmuir adsorption isotherm is obtd, the adsorption of STAB on HMX is reversible and therefore physi-... 

Facile Three-Step Preparation of 180-Labeled Diastereomeric Ammonium Salts of Thymidine Cyclic 3, 5 -Monophosphate... 

This ammonium salt has two different P cartxsns, labeled and p2-... 

The tetrahedral geometry is found most commonly at a normal sp carbon centre. However, it may be found in other situations. For example, there is no need for the chiral centre to be a carbon atom, i.e. other tetravalent asymmetrical centres such as a quaternary ammonium salt would suffice. In passing, it ought to be noted that there needs only to be a very small difference in the four groups in order for optical activity to arise. This may be illustrated by the isotopically labelled sulphone, R1R2S180160, which is optically active. 

Fractional distillation of NO provides another effective route and, as the heavier isotope of oxygen is simultaneously enriched, the product has a high concentration of N 0. Many key nitrogen compounds are now commercially available with N enriched to 5%, 30% or 95%, e.g. N2, no, NO2, NH3, HNO3 and several ammonium salts and nitrates. Fortunately the use of these compounds in tracer experiments is simplified by the absence of exchange with atmospheric N2 under normal conditions, in marked contrast with labelled H, C and O compounds where contract with atmospheric moisture and CO2 must be avoided. 

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