Deuterated compounds impurity

The aliquots of the solution-state chemical synthesis samples were directly injected into a standard HPLC-NMR probe by using a robotic liquid handler. The NMR software was used to automatically find and suppress the intense NMR signals from any non-deuterated solvents used, typically using the WET sequence [5]. Unlike the characterisation of impurities in organic compounds (see the next section) or drug metabolites (see the appropriate chapter in this volume) where the proportions of the analytes can be very different, combinatorial chemistry samples tend to be all of similar quantity and this simplifies the analysis in that it is not usually necessary to worry overly about carry-over of material from sample to sample, nor it is necessary to readjust the NMR spectrometer receiver gain after every sample, thus saving considerable machine time. 

The following table lists the residual peaks that are observed in the H NMR spectra of common deuterated organic solvents. These peaks are generally attributed to the nondeuterated parent compound that serves as an impurity and are marked with an asterisk. In addition, other less significant peaks often arise due to other impurities. 

From the analysis of residual v(CH) bands of the deuterated methyl or methylene groups, it is possible to determine the nature of isotopic impurities. The comparison of their intensity to the ones relative to the pure compound indicates their percentage. So, from CD.HCHDC CH spectrum analysis, we have found that a sample of CDaCDjC CH contained 4% of l-butyne(Di-3,4,4,4) and 6% of l-butyne(D4-3,3,4,4) In the same manner, we have found that the deuterium impurities of... 

If liquid water is a mixture of some components, it is natural to expect that at some conditions they may undergo liquid-liquid phase transition, similar to the one in the binary liquid mixtures. Contrary to the mixtures of chemically different compounds, concentrations of components in liquid water cannot be imposed independently on temperature and pressure. Besides, the universality class of the liquid-liquid critical points of one-component isotropic fluids may differ from the universality class of Ising model [6]. However, many other features should be similar in both cases. Even when the liquid-liquid transition is unachievable experimentally due to crystallization or due to other processes, its critical point may have a strong distant effect on the properties of liquid water at ambient conditions. In a two-component binary mixture, effect of both the liquid-vapor and the liquid-liquid critical points on fluid properties should be taken into account [62]. The liquid-liquid critical point may be distant in terms of temperature, pressure, and also external field , which may be varied by addition of impurities or by small variation in molecular structure (for example, by deuteration) [63, 64]. For example, mixture of 3-methylpyridine with heavy water possesses a closed-loop... 

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