Sodium films

Materials 1,3-Dioxolane (1) and 1,3-dioxepane (5) were prepared and purified conventionally. Compound 1 contained no impurities detectable by GLC, but 5 contained a trace of tetrahydrofuran (THF) which could not be removed even by distillation on a Fenske column with a reflux ratio of 50 1 4-methyl-l,3-dioxolane (4) was prepared by Astle s method [10]. All monomers were dried preliminarily by storage over LiAlH4 in reservoirs attached to a conventional high-vacuum line fitted only with all-metal valves, and then stored with liquid Na-K alloy until used. Methylene dichloride was purified conventionally, distilled on a Normatron 1.5 m column, dried i.vac. over LiAlH4 on a conventional high-vacuum line, and then stored for 24 h over a fresh sodium film immediately before use, in a reservoir attached to the vacuum line. 

Note It is very dangerous to bring CH2Cl2 into contact with a sodium film except i.vac. and after drying it very carefully. 

A detailed study of the electronic, vibrational, and e.s.r. spectra of a series of substituted dipyrromethane complexes of nickel(ii) has been reported." The reduction of the nickel(ii) 1,19-diethoxycarbonyltetradehydrocorrin cation with a sodium film in THF under high vacuum gives both one- and two-electron reduction products. The one-electron reduction product is a very stable free radical, and the other product is formulated as a Ni" species with the two extra electrons located in ligand n-orbitals. The structures of nickel-(ii)-octaethylporphin and nickel(ii)-deoxophylloerythrin methyl ester-1,2-... 

I. Sodium. Probably the best known active hydrogen remover is sodium. When used outside a vacuum system, for instance as sodium wire to dry solvents, the sodium is little more than a support for a skin of sodium hydroxide. Inside a vacuum system, however, one can prepare films of sodium metal and one can prepare really clean sodium which will give a colourless solution of sodium ethoxide (see Section 5.2.1.). The method of making sodium films for the removal of acidic compounds from liquid reagents will be described and also a very much less well-known method involving sodium vapour and colloidal sodium. 

Evidently, the types of compound compatible with this mixture are not many, but it has been used successfully for various 1,3-dioxacycloalkanes and hydrocarbons. It must not be used with halogen compounds although chloro- and bromo-alkanes can be dried safely over sodium films, provided that they are initially at least Grignard dry and free of oxygen. In the author s laboratory specimens of CHjClj and MeBr which had been over sodium films under vacuum for several years were analysed and found to contain only traces of the Wurtz-condensation products. 

The results obtained by Citrin and coworkers are shown in Figure 3. For sodium clusters on a metal support (wigl ML Kr/Pt, filled circles), the Kr 4s binding energy decreases with cluster coverage. This shows that the Fermi levels of the sodium and platinum equilibrate. As the sodium is added, the work function decreases from the value for platinum to the value for a sodium film. Conversely, the Na 2p peak position does not shift with cluster coverage. The rapid electron transfer between the sodium and platinum prevents any accumulation of charge on the cluster in the photoemission final state (41). 

The cobalt(II) corrole anion prepared as above was characterized primarily by electron spin resonance (esr) and absorption spectroscopy. When prepared via sodium film reduction, the cobalt(II) corrole oxidizes rapidly to the corresponding Co(III) corrole on exposure to air. When prepared by the other methods, it is moderately stable in air in the presence of a reducing agent. Attempts to prepare the neutral form of the initial Co(II) corrole anion, by protonation with perchloric acid, resulted in formal oxidation to the Co(III) derivative. Interestingly, further protonation of the Co(III) corrole with perchloric acid led to what appeared to be a protonated Co(III) corrole. Certainly, the absorption spectrum of this species is similar to that of the corresponding neutral nickel(II) corrole complex. However, the exact nature of this protonated material has not been fully elucidated. 

The stoichiometric EDA complexes between anthracene and sodium were prepared in the following manner The apparatus consisted of two vessels ccmnected with a tube equipped with a glass filter. One of the vessels (I) contained anthracene and the other (II), sodium evaporated film. The solvent tetrahydrofuran (THE) was introduced into the vessel (I) by vacuum distillation to prepare the anthracene solution, which was brought into contact with the sodium film by being passed... 

The most obvious reason for the removal of undrained sodium films stems from the chemical activity of the metal. Scrap piles of sodium-system components, if left uncleaned, present the possibility of hydrogen fires and the added hazard of caustic burns to personnel. This is particularly true if the scrap is exposed to rain or humid atmospheric conditions. Similarly, in making extensive repairs to sodium systems or components, the removal of sodium facilitates working conditions, since it eliminates the possibility of the above-mentioned complications. After sodium recleaning, maintenance can be performed by personnel who need not be trained in the specific disciplines of sodium technology. 

It is a desirable objective to clean the least complex arrangement possible, and therefore, the system should be kept simple. For a complex arrangement, components or sections of systems should be disassembled and cleaned individually. In the recleaning of sodium films, either alcohol or steam is used in the initial phase, followed by a final water rinse. Both of the initial agents have advantages and disadvantages for the recleaning application and, thus, the choice of technique is influenced by the application. 

Based on this coefficient and assuming the validity of Pick s law, it is calculated that at 400°P. and for humid-gas concentrations in the 9 to 50% water range, approximately 400 hours would be required for a 1-inch thick pocket of sodium to react. This order of magnitude calculation indicates the desirability of extreme turbulence in recleaning. To avoid high temperatures, such turbulence should best be introduced by a humid gas of low-water content or after the bulk of the thin sodium films of a system have been reacted. The diffusion rate also points out the undesirability of relatively deep, stagnant pockets. 

The first point is that the carbonation of the sodium films should not present any particular problem. 

C32H16CUN8 Copper(II)phthalocyanine di-anion Nr. 122 Sodium film reduction/ THF EPR/ 2.0021 ) 67Clal... 

Tisja and Tci are obtained by multiplying the nominal average central subassembly temperature rise (ATcsa)j sodium film drop (ATAm) and cladding middle to outer surface drop (Aid) with appropriate hotspot factors as follows ... 

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