Reversible processes ambient temperature

Oxygen addition to thiyl radicals is reversible at ambient temperatures [4, 9-11, 88] and appears to be diffusion controlled [4,88]. In glasses it takes place even at 77 K if the matrix allows oxygen to diffuse [13]. ESR and optical absorption spectra of some O-labelled RSOO radicals obtained in methanol glasses at 77 K are shown in Figure 1. A gas phase rate constant has been reported to be about 10 cm molecule" s within 216-258 K temperature range, although the equilibrium is shifted towards the reactants and this allowed this process to escape detection in the past [89]. 

The role of the stress in embrittlement and stress-corrosion processes has been examined in some detail by employing the slow strain-rate technique . Specimens of alloy 7179-T651 tested in air or in vacuum after pre-exposure to water at 70° C or in water at various potentials at ambient temperature exhibited a reversible embrittlement in excess of that arising from testing in moist air . The embrittlement was attributed to hydrogen absorption, and recovery was thought to be due to loss of hydrogen (particularly under vacuum) or to diffusion to traps. Potentiostatic tests revealed... 

By introducing redox-active N-methyl-4,4/-bipyridinium ion (mbpy+) to the oxo-centered triruthenium cores, a series of triruthenium derivatives bearing two or three axially coordinated mbpy+ were prepared by Abe et al. [12, 13]. Electrochemical studies indicated that these mbpy+-containing triruthenium complexes afforded a total of seven to nine reversible or quasi-reversible redox waves in acetonitrile solutions at ambient temperature. Of these redox waves, four or five one-electron redox processes arise from RU3 -based oxidations or reductions involving five or six formal oxidation states, including... 

The immobilization of dissolved chemical species by adsorption and ion exchange onto mineral surfaces is an important process affecting both natural and environmentally perturbed geochemical systems. However, sorption of even chemically simple alkali elements such as Cs and Sr onto common rocks often does not achieve equilibrium nor is experimentally reversible (l). Penetration or diffusion of sorbed species into the underlying matrix has been proposed as a concurrent non-equilibration process (2). However, matrix or solid state diffusion is most often considered extremely slow at ambient temperature based on extrapolated data from high tem-... 

A number of different equilibria may be present in the solution of a chiral substrate and the added chiral auxiliary compound. When all equilibrium processes are fast on the NMR timescale at ambient temperature, an averaged spectrum of shifts is observed. This is also the reason why peak coalescence of the anisochronous nuclei is observed when a racemic auxiliary compound is used5,81. The observed anisochrony of the enantiomers AR sS is highest when the chiral auxiliary compound is enantiomerically pure. AR sS decreases as the enantiomeric purity of the chiral auxiliary compound is reduced. AR sS changes its sign when the chirality of the chiral auxiliary compound is inverted (peak reversal). 

When the alcohol adduct from the allenylzinc reagent and diisopropyl ketone was treated with 80 mol% of allenylzinc bromide in HMPA, a mixture containing 12% of diisopropyl ketone and 88% of recovered alcohol was obtained after 7 days at ambient temperatures (equation 1). Thus, it may be deduced that the allenylzinc additions are reversible. Presumably, the propargyl adducts are intrinsically favored, but steric interactions between the R1 and R2 substituents in the propargyl product favors an increased proportion of allenyl adducts in a reversible process (see Table 1). HMPA would expectedly facilitate reversal of the addition by decreasing the ion pairing between the alkoxide anion and ZnBr cation of the adducts. This expectation was subsequently confirmed by a study of solvent effects. 

A polyhedron silsesquioxane ladder polymer containing polymerizable components was prepared in a three-step process to address this concern. The process initially entailed preparing the reversible addition-fragmentation transfer (RAFT) ladder iniferter, polysilsesquioxane dithiocarbamate. This intermediate was then polymerized with methyl methacrylate at ambient temperature by irradiating with ultraviolet (UV) light and poly(si Isesquioxane-g-methyl methacrylate) was obtained. 

Theoretical analysis indicated that the first goal, reduced energy consumption, was realistic. A reversible acid gas removal process separating acid gases from a 1000 psia crude gas containing 30 mol % CO2 would reject carbon dioxide at ambient temperature and pressure, and be a net energy producer. 

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