Special Experimental Techniques

The Schotten-Baumann reaction between dicarboxylic acid dichlorides and diamines can be performed not only in organic solvents, but also, by means of a special experimental technique known as interfacial polycondensation (see Examples 4-5 and 4-11). Both variants have the advantage of short reaction times at low temperature with simple equipment. 

Nitrenes, as is the case with other electron-deficient high energy species, are sufficiently short-lived that special experimental techniques are required for positive verification. Bonding patterns, such as those above, can just as readily involve nitrenoids which are electron-deficient in character but not truly monovalent. Here we will not attempt to make a careful distinction between these intermediates, so long as cyclization is the synthetic outcome. 

The field of droplet statistics involves a strong mutual dependence between the experimental techniques which are used to obtain the drop-size data and the mathematical formalism required to interpret and summarize the data. Special experimental techniques may lead to drop-size distributions, averages, and measures of dispersion that are appropriate to no other technique. Any attempt to restrict all techniques to the use of certain prescribed distributions together with certain mean diameters appears doomed. At present, only general outlines of the mathematical criteria appropriate to all techniques are discernible. These criteria merely prescribe that the parameters appropriate to drop-size analysis should have known distributions, and that the various measures of... 

McFarlane, W. (1987). Special experimental techniques in phosphorus NMR spectroscopy. Methods in Stereochemical Anal., 8 (Phosphorus-31 NMR Spectrosc. Stereochem. Anal.), 115-150. 

The faithful representation of the shape of lines broadened greatly by dipolar and, especially, quadrupolar interactions often requires special experimental techniques. Because the FID lasts for only a very short time, a significant portion may be distorted as the spectrometer recovers from the short, powerful rf pulse. We saw in Section 2.9 that in liquids a 90°, t, 180° pulse sequence essentially recreates the FID in a spin echo, which is removed by 2r from the pulse. As we saw, such a pulse sequence refocuses the dephasing that results from magnetic field inhomogeneity but it does not refocus dephasing from natural relaxation processes such as dipolar interactions. However, a somewhat different pulse sequence can be used to create an echo in a solid—a dipolar echo or a quadrupolar echo—and this method is widely employed in obtaining solid state line shapes (for example, that in Fig. 7.10).The formation of these echoes cannot readily be explained in terms of the vector picture, but we use the formation of a dipolar echo as an example of the use of the product operator formalism in Section 11.6. 

A carbene (carbenoid) is a species of general formula (23-XLIV), in which X and X represent a great variety of nominally univalent groups. As compounds of divalent carbon, carbenes are short-lived in the free state, but they have been studied by special experimental techniques, as noted in Chapter 10. The more stable carbenes are those in which the electronic structure can be represented by the resonance (23-XLV). When this is com-... 

It has been already indicated (Fig. 7) that micelles can lead to an essential acceleration of the adsorption process. Therefore, special experimental techniques are necessary for its investigation, allowing measurements of the dynamic surface tension in a time interval of milliseconds. The maximum bubble pressure method [78, 81, 83, 89,90,93] and the oscillating jet method [77, 82, 86, 87, 88, 90, 92, 93, 156] are most frequently used for these purposes. The inclined plate method [83, 89, 90, 93], the method of constant surface dilation [85] and the drop volume method [84] have been used also for slow adsorbing surfactants. 

Investigations of ablation require special experimental techniques. For example, when glass or polyamide fibre-reinforced high-temperature phenolic resins were subjected to a high-temperature plasma arc, the mass loss rate could be represented by an Arrhenius plot as shown in Figures 3.75 and 3.76. 

In conclusion, we describe two phenomena between which there exists a certain relationship. The first phenomenon consists of a high near-surface conduction of ice the near-surface layer, several nanometers in thickness, may possess a conductivity comparable with that of a macroscopic crystal. Detection of this phenomenon necessitates use of special experimental techniques (guard ring) for measuring conductivities and undoubtedly indicates a peculiar state of the protonic system in the near-surface layer" . 

Using the experimental results with low conversions and the special experimental technique Jby Towell Martin (11), the order of propane or propylene decomposition was obtained In the copyrolysls system. It was revealed that the rate equations for the component In question were a function of only one concentration variable as follows ... 

The determination of diffusion constants in metals may be made by a number of rather special experimental techniques,... 

The progress in this area is, to a significant degree, linked to the exploitation of specialized experimental techniques such as neutron reflection, ellipsometry, fluorescence... 

---