Thermal migration

In order to obtain dyeings that do not exhibit thermal migration behavior it is necessary to carefully select the dyes and the conditions of subsequent... 

J.V. Barth, Transport of adsorbates at metal surfaces from thermal migration to hot precursors. Surf. Sci. Rep. 40, 75-149 (2000). 

This is also a [1, 5] thermal migration of hydrogen. The hydrogen migrates so fast in preference to the methyl group that at room temperature one sees a singlet for the methyl group. 

Remarkable regioselectivity was observed in the thermal migration of the tetra-substituted alkene Z-83. Hydroboration of this compound furnishes only the migration product in the direction of the ethyl group. Furthermore, the migration was stereoselective providing, after the standard amination sequence, the benzylic amine 85 in 46% yield. The diastereoselectivity was 95 5 between C(l) and C(2) and >99 1 between C(2) and C(3) (Scheme 17) [7, 8, 13],... 

The NEMCA effect is closely related to classical promotion and to the phenomenon of metal-support interactions (MSI) with oxide supports and that MSI can be viewed as a self-driven NEMCA microsystem where the promoting O2- ions are thermally migrating from the support to the dispersed catalyst nanoparticles and replenished in the support by gaseous 02 [v]. 

The rate constant of the dark bleaching resulting from the thermal migration of the aryl group and the activation energy depended on the structure of the photochromic compounds. 

The influence of the temperature of nitration of 4-alkyl-phenol acetates was examined by the same authors [40] and simultaneously and independently by Schofield and associates [41]. The latter examined the thermal migration of the nitro group ... 

There was however a possible case of thermal migration of a silicon on a simple olefin in the largely overlooked 1985 report by Conlin [6] that a-methylenesilacyclobutane 1 cleanly isomerized to a mixture of silacyclopentenes 3 and 4 (Eq. 8). Although no mechanistic studies were performed, Conlin boldly proposed that this reaction proceeded through the intermediacy of carbene 2 which, if correct, would make this the sole example of a thermal isomerization of an untwisted olefin to a carbene. 

Gaillard C, Chevarier N, Den Auwer C, Millard-Pinard N, Delichere P, Sainsot Ph (2001) Study of mechanisms involved in thermal migration of molybdenum and rhenium in apatites. J Nucl Mater 299 43-52... 

The experimental results on the HD/Ar system can be explained as follows. The H and D atoms initially formed in the irradiated HD/Ar sample may encounter an HD molecule located in a substitutional site of solid Ar in the course of their thermal migration. The D atoms may react with HD to form an H atom and a D2 molecule in an exothermic process (AG < 0). On the other hand the H atom reaction with HD is an endothermic process (AG > 0) and is unlikely to occur [77, 94] ... 

Intrinsic sources of porosity are the molar volume change (due to the formation of the product) and the porosity generated by the thermal migration. Figure 28 shows the relationship between the molar volume of the reactants and the product for selected refractory materials. The lines represent a value of x in the relationship Fp = jcFr, where Fp and Fr are the molar volumes of the product and reactants, respectively. The figure shows that the formation of TaC, B4C, for example results in a porosity of about 10%, while the formation of SiC, MoSi2, results in a porosity of about 30%. The other intrinsic source porosity is thermal migration (the Soret... 

Z. A. Munir and L. L. Wang, The contribution of thermal migration to pore formation during SHS reactions, in Proceedings of the First US-Japan Workshop on Combustion Synthesis, Y. Kaieda and J. B. Holt (Eds), National Research Institute for Metals, Tokyo, Japan, 11-12 January 1990, pp. 123-137. 

Haase [17] has reported some observations on thermo-osmosis of water through cellophane membrane with and without deposition of copper ferrocyanide in the pores. A well-authenticated instance of thermal migration of a liquid against a hydrostatic pressure through a permeable barrier is the fountain effect in liquid He II. Like thermoosmosis, this process gives rise to a well-defined stationary pressure difference. 

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