Promising New Methods

Ionization potentials of transient species have been measured by photoelectron spectroscopy and this technique may be sufficiently sensitive to be used for monitoring energy states of diatomic and perhaps polyatomic product molecules. Although quantitative energy disposal data have not been reported yet, the photoelectron spectroscopic method appears to be useful for diatomics which cannot be observed by conventional spectroscopic techniques. Like laser-induced fluorescence, the Franck-Condon factors of the ground state and the ion must be known to obtain vibrational populations from the intensity data. 

Measuring Doppler widths of rotational lines by laser-probe techniques gives velocity distributions in just the same way as measuring Doppler widths of atomic lines by conventional means. In this method a laser beam with a very narrow band width is tuned over the spectral line to determine the profile of the Doppler broadened line. The line shape can be interpreted to give the average velocity of the product. As yet, this method has been applied only to rotational energy transfer studies however, with the availability of mode-locked lasers providing narrow band widths, this procedure may become more widely used. 

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Nitration of aromatic rings is possible by use of Pd(N03)2[356], Pd(OAc)2-NaN02[357], Pd(0Ac)2-N02[358], and Pd(0)-NO2[359], The nitration can be carried out fully catalytically by Pd(0Ac)2-N02 and oxygen. This reaction offers a promising new method of nitration without using mixed acids of HNO3 and H2SO4. 

Stable carbon isotopes (see Chap. 1) provide a promising new method of validating intrinsic bioremediation. Carbon has two stable isotopes, with 12C comprising 98.89% and 13C comprising 1.11% of the total natural abundance [476]. Because of the magnitude of this abundance gap, the ratios of 13C to 12C in carbon-bearing compounds are expressed as per mil (%o) differences relative to a standard (i.e., <513C vs PDB,see Chap. 1). 

A very promising new method for converting oxiranes, as well as ketones, into oxetanes has recently been reported. This method uses the carbanion of dimethyl(N-tosyl)sulfoximine and gave good yields in the several cases reported. When this reagent is employed with ketones, oxirane formation is presumably an intermediate stage, but the oxirane is not isolated. The method thus provides an excellent synthesis of spiro-oxetanes from ketones, as the example with camphor in equation (85) shows (79JA6135). 

Several alternative methods for the determination of sialic acid in body fluids and tissues have been described. Most of these methods make use of the classic periodate-TBA assay in combination with purification using HPLC [13]. Another method makes use of fluorometric HPLC of sialic acids after derivatization with a fluorogenic compound [9]. The most promising new method for the determination of free sialic acid in urine (and probably also other body fluids and tissues) is the HPLC-tandem mass spectrometry method [19]. This method is rapid, accurate, and sensitive, and is more robust than earlier methods. The only disadvantage is the expensive equipment that is required, which makes it only economical for specialized metabolic laboratories. Since this equipment is used for many different metabolic assays, the investment is certainly warranted, and nowadays almost essential for any metabolic laboratory. 

The preceding examples show the possibilities and also the present limitations of PTC. The conversion of the heterocycle to its /V-oxide or complex-ation of benzene with Cr(CO)3 promote reaction of unactivated compounds. But these approaches are based on a multistep procedure. A very promising new method is the one-step reaction of unactivated aryl (and heteroaryl) halides by way of the SRN1 mechanism developed by Bunnett.232,233 This has been applied to heterocyclic molecules mainly by Wolfe and Carver.234 A pyridine derivative serves as an example. 

A promising new method for the preparation of thiobarbituric acids (112) involving the reaction of carbon suboxide with various arylthio-ureas was reported by Baranova et al.2il... 

When using dithioacetals as intermediates the most tedious step is often their hydrolysis to carbonyl compounds. As a consequence, many methods have been developed to realize that conversion and, in their review [43], Grobel and Seebach give experimental details for most of the procedures known at that time. In view of the fundamental importance of dethioacetalization, we now describe some promising new methods that have appeared since. 

Essentially, any technique applicable to the measurement of physicochemical properties of compounds may be considered for the study of reaction rates, and it is up to the imagination of the researcher to exploit the principles behind the technique and devise an experimental method. A number of extremely useful electrochemical techniques are covered in Chapter 6, and Chapter 8 includes a very promising new method combining calorimetric and FTIR measurements. Mass spectrometry, a field in constant development and with an abundant literature, is ideally suited for the study of wide-ranging reaction types in the gas phase, including those related to atmospheric investigations, but is beyond the scope of this chapter. 

As described briefly in Chapter 3, a promising new method of electronic structure calculation utilizing combined molecular-dynamics and density-functional theory has recently been developed by Car and Pari-nello (1985). This approach has recently been applied to cristobalite, yielding equilibrium lattice constants within 1% of experiment (Allan and Teter, 1987), as shown in Table 7.2. New oxygen nonlocal pseudopotentials were also an important part of this study. Such a method is a substantial advance upon density-functional pseudopotential band theory, since it can be efficiently applied both to amorphous systems and to systems at finite temperature. 

In summary, a promising new method, REPSWA, has been compared and contrasted to existing techniques. Due to its mathematical structure, REPSWA scales linear with system size and has been shown to perform well in model problems. It can easily be combined with parallel tempering and Hybrid Monte Carlo methods to form interesting and exciting novel sampling schemes. These will be described in future work. 

We should, however, always be aware of that speculations in reaction mechanisms may be wrong. If a selection of a test solvent was based on a hypothesized reaction mechanism which later on was found to be false and if this erroneous assumption led to a rather narrow selection of tested solvents, and if the reaction failed in the solvent selected, there is a risk that a promising new method has been overlooked. A more dispersed set of test solvent would have made it possible to detect suitable solvent and would also have revealed that the mechanistic assumptions were wrong. 

For some important classes of compounds, methods have been developed to predict EOS parameters, including binary interaction parameters, from molecular structure. The PSRK method [44] has found significant use, and a promising new method is known as VTPR [45]. 

One of the most promising new methods of producing syn gas from methane is by partial oxidation with oxygen directly (e.g., see reference [76]) ... 

Method (1) can not (yet ) be used for proteins. Method (2) can be used to solve any protein structure de novo, but this method requires testing and measuring dozens of heavy atom derivatives, and is hardly used any more. Method (3) allows the fast determination of de, novo protein structures, provided they can be labelled with seleno methionine (expression in E. coli). Extremely promising new methods use the anomalous signal of soaked-in halide ions, or the signal of native sulfurs. When these, methods deliver what they promise, they allow any new structure to be solved in a matter of weeks. Method (4) is very fast it usually takes less than a week, but it requires that the structure of a similar protein be available, which is not always the case. This method is extremely useful in solving the structures of a protein complexed with a series of inhibitors or other ligands. 

Cellulose, which Is one of the most abundant organic substances found In nature, has been extensively studied by various techniques such as x-ray scattering, electron microscopy, IR and Raman spectroscopy, NMR spectroscopy etc. However, the crystal structure and noncrystalline state are not yet solved for cotton, ramie, bacterial and valonla celluloses which can be easily obtained in pure form. Cross-polarization/magic angle spinning(CP/MAS) C NMR spectroscopy is a promising new method to study these unsolved problems of cellulose, because this method is very sensitive to local molecular conformations and dynamics. 

The in situ procedure as proposed by Sonnet et al. (18) is much more attractive for synthetic applications. With the use of only a moderate excess of monopersulfate (C=C KHSO5 = l 2-2.4), they achieved an 80% yield for the epoxidation of oleic acid methyl ester and 81-96% for the epoxidation of various plant oils. It is a twophase reaction with a crown-ether as phase-transfer catalyst yet a considerable amount of inorganic waste (six times the weight of the product) is produced. In a recent work (21), the phase-transfer catalyst was replaced by acetonitrile as a polar solvent. In summary, epoxidation by dioxiranes is a promising new method for oleo-chemistry, especially because it also works in combination with metal catalysts to influence diastereoselectivity (22) an enantioselective epoxidation with sugardioxiranes has also been reported (23). 

This promising new method, however, has potential drawbacks, namely interference from Fe at approximately 248 nm. Additional testing of LIBS is required to understand the effects of soil properties such as texture, moisture content, and minera-logical composition (e.g., silicon content) on LIBS measurements. 

Some promising new methods are not provided in this table however, they are discussed in Section 5.2.4 below. The variety of identification and differentiation methods is extensive only a few are implemented in the routine analysis conducted in commercial laboratories, and even fewer in the microbiology laboratories of breweries. A list of some of the established and reliable routine methods for rapid yeast identification is found in Section 5.2.3. Which method is applied in brewery laboratories or combined with the established routine methods depends on the practicability and the degree of aceeptance for new techniques, which require special training and knowledge of yeast handling. 

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