Control of Coupling

Hydrogenation of anilines normally gives cyclohexylamines and varying amounts of the coupled products, dicyclohexylamines. The ratio of these products is influenced by temperature, catalytic metal, support, additives, and solvent. It is possible to exert substantial control over the product composition. Coupled products increase with increasing temperature (23). 

In a study on the influence of supports on rhodium, the amount of dicyclohexylamine was found to decrease in the order carbon barium carbonate alumina barium sulfate calcium carbonate. Plain carbon added to rhodium-on-alumina-catalyzed reactions was found to cause an increase in the amount of dicyclohexylamine, suggesting that carbon catalyzes the formation of the intermediate addition product (59). 

The amount of coupled product was found to depend importantly on the catalytic metal a sequence for increased coupling to dicyclohexylamine was found to be Ru Rh Pd Pt (59), a sequence that reflects one reason for the industrial preference for rhodium and ruthenium in hydrogenation of anilines. 

The extent of coupling is also influenced by the solvent. In the hydrogenation of aniline over ruthenium oxide, coupling decreased with solvent in the order methanol ethanol isopropanol t-butanol. The rate was also lower in the lower alcohols, probably owing to the inhibiting effect of greater concentrations of ammonia (44). Carboxylic acid solvents increase the amount of coupling (42). 

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K.Y. Chang and W.L. Luyben. Design and control of coupled reactor/column systems- Part 3. A reactor/stripper with two colnmns and recycle. Comput. Chem. Eng., 21(l) 69-86, 1997. 

LT048 Moinuddin, S. G., S. Hishiyama, M. H. Cho, L. B. Davin, and N. G. Lewis. Synthesis and chiral HPLC analysis of the dibenzyltetrahydrofuran lignans, larreatricins, 8 -epi-larreatricins, 3,3 -didemethoxyverrucosins and meso-3,3 -didemethoxynectandrin B in the creosote bush (Larrea tridentata) evidence for regiospecific control of coupling. Org Biomol Chem 2003 1(13) 2307-2313. 

In conclusion, the concept of SPODS as discussed on atomic systems in the preceding sections is readily extended to the control of coupled electron-nuclear... 

Control of coupled turbomachinery and positive displacement machinery,... 

Wu, Y., 2011. On the modeling and control of coupled multi-loop thermosyphons. In Applications of Mathematics and Computer Engineering, 2011 American Conference on Applied Mathematics, pp. 105—110. 

The control of the airborne sound location system, the coupling monitor and the real-time evaluation of all signals, including the echo indications from the ultrasonic instrument, is carried out on two additional boards in the PC. The graphic user interface (under Windows 95), including online help, enables an easy operation of the system. The evaluation program links all echo indications in real time with the probe position and displays them in a graphic repre-... 

Potential-step teclmiques can be used to study a variety of types of coupled chemical reactions. In these cases the experiment is perfomied under diffrision control, and each system is solved with the appropriate initial and boundary conditions. 

Wang C, Mohney B K, Williams R, Hupp J T and Walker G C 1998 Solvent control of vibronic coupling upon intervalence charge transfer excitation of (NC)gFeCNRu(NH3)g- as revealed by resonance Raman and near-infrared absorption spectroscopies J. Am. Chem. Soc. 120 5848-9... 

Three-component coupling with vinylstannane. norbornene (80). and bro-mobenzene affords the product 91 via oxidative addition, insertion, transme-tallation, and reductive elimination[85]. Asymmetric multipoint control in the formation of 94 and 95 in a ratio of 10 1 was achieved by diastereo-differ-entiative assembly of norbornene (80), the (5 )-(Z)-3-siloxyvinyl iodide 92 and the alkyne 93, showing that the control of four chiralities in 94 is possible by use of the single chirality of the iodide 92. The double bond in 92 should be Z no selectivity was observed with E form[86]. 

An important advancement in carburizing has been the development of diffusion models to calculate the carbon gradient as a function of time as the gas composition and temperature change (13). Such models can be coupled with computer control of the gas composition and temperature to produce desired carbon profiles. 

Monolayers of alkyl chains on siUcon are a significant addition to the family of SAMs. An abiUty to directly connect organic materials to siUcon allows a direct coupling between organic materials and semiconductors. The fine control of supedattice stmctures provided by the self-assembly technique offers a route for building organic thin films with, for example, electrooptic properties on siUcon. 

Atomic Absorption/Emission Spectrometry. Atomic absorption or emission spectrometric methods are commonly used for inorganic elements in a variety of matrices. The general principles and appHcations have been reviewed (43). Flame-emission spectrometry allows detection at low levels (10 g). It has been claimed that flame methods give better reproducibiHty than electrical excitation methods, owing to better control of several variables involved in flame excitation. Detection limits for selected elements by flame-emission spectrometry given in Table 4. Inductively coupled plasma emission spectrometry may also be employed. 

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