Oxygen-free conditions

Anaerobe An organism that grows without air or requires oxygen-free conditions to live. 

The corrosion of tin by nitric acid and its inhibition by n-alkylamines has been reportedThe action of perchloric acid on tin has been studied " and sulphuric acid corrosion inhibition by aniline, pyridine and their derivatives as well as sulphones, sulphoxides and sulphides described. Attack of tin by oxalic, citric and tartaric acids was found to be under the anodic control of the Sn salts in solution in oxygen free conditions . In a study of tin contaminated by up to 1200 ppm Sb, it was demonstrated that the modified surface chemistry catalysed the hydrogen evolution reaction in deaerated citric acid solution. 

Bismuth Niobium is resistant to bismuth at temperatures up to 560°C but is attacked at higher temperatures and is therefore not considered a suitable container for handling liquid bismuth even under oxygen-free conditions Furthermore, the stress-rupture properties of niobium are significantly lowered when the metal is tested in molten bismuth at 815°C . 

The equilibrium concentration of dihydrophenanthrene under oxygen-free conditions is very small. However, this reaction, in the presence of Oa and I3, has been developed to the point where it is a good method for ring formation. 

Dead bodies can be naturally mummified under a variety of environmental conditions, such as (1) at extremely low temperatures, about and below the freezing point of water, in extremely cold regions of the world (2) in very dry and hot environments, as in desert areas and in some caves and rock shelters or (3) under anaerobic (oxygen-free) conditions, as in bogs (see Chapter 8). 

Although it has been known since 19051 that very pure chromium metal reacts with acids, under oxygen-free conditions, to produce large quantities of chromium (II), this approach to the preparation of chromium(II) compounds has not been developed. Rather, syntheses generally involved (1) reduction of chro-mium(III), either by electrolytic means or by chemical agents (for example Zn/Hg), or (2) metathetical procedures. Both methods are inefficient and often lead to impure products. Recently2-8 extensive use of reactions between electrolytic chromium and various acids has led to the synthesis of a wide variety of chromium (II) complexes which would be considerably more difficult to prepare by other methods.9-11... 

Chiral allenylpalladium complexes have been prepared from non-racemic propargylic chlorides and Pd2(dba)3-PPh3 [88]. Although nominally stable, these complexes were found to racemize under certain conditions (Eq. 9.108). Reagents prepared under oxygen-free conditions racemize more slowly than those prepared in... 

Co complexes, Buchwald reported the Ti-catalyzed carbonylative coupling of enynes-the so-called Pauson-Khand-type reaction [28]-and realized the first such catalytic and enantioselective reaction using a chiral Ti complex [29]. Here, a variety of enynes were transformed into bicyclic cyclopentenones with good to high ee-values however, several steps were required to prepare the chiral Ti catalyst, while the low-valent complex proved to be so unstable that it had to be treated under oxygen-free conditions in a glove box. 

The reaction of ReClj with R4NCI (R = Et or Pr) (1 1) under anhydrous, oxygen-free conditions produces (R4N)[ReCl5]. The solubility, i.r. spectral, and magnetic properties of these air-stable salts suggest that the anions are polymeric, and they react with unidentate ligands [L = py, MeCN, H2O, DMF,... 

Most repository sites under consideration for commercial spent fuel disposal are in reducing environments, such as in Boom clay formations of the Mol site, Belgium, where U02 is thermodynamically stable. In oxygen-free conditions, Spahiu et al. (2002) have shown that fuel in an... 

Caution. All operations must be carried out under anhydrous oxygen-free conditions using standard Schlenk techniques. Tetramethyltin is toxic on inhalation and/or other contact and is also flammable. Dimethylsulfoxide is an irritant and can penetrate the skin very easily. Contact with the skin by either reactant should be avoided. It is necessary to carry out the reaction in a well-ventilated fume hood. 

Thus the heat of explosion (under oxygen-free conditions) has been determined by Wheeler, Whittacker and Pike [13] to be — Q = 77.6 kcal/mole, i.e. 853 kcal/kg, which is close to the value reported by Naotim [1]. 

Together with azobenzene, other diaryldiazenes have also been found to form complexes with nickel(O) and PEt3. All the complexes are air-unstable and have been prepared in rigorous anhydrous and oxygen-free conditions according to equation (41).210... 

BM),1941 1942 has been obtained according to equation (194). The synthesis requires strictly oxygen-free conditions, but the solid compound is relatively stable in the air. 

Caution. Butyllithium reacts violently with water and should be handled under an inert atmosphere. Until the ethanol quench, all manipulations are performed under anhydrous, oxygen-free conditions. To minimize chances for an explosion, diethyl ether should always be tested for peroxides prior to distillation from LiAlH . Additionally, under no circumstances should the distillation still be allowed to dry.5... 

Foetal and neonatal livers contain exceptionally high levels of copper compared to the adult organ. Thus, the livers of new-born rats contain as much as 20 times the level of copper and zinc metallothionein as that found in 70-day-old rats.1150 Again, a metallothionein from foetal bovine liver contained eight copper and two zinc atoms per molecule of protein.1151 These proteins can only be isolated with difficulty under oxygen-free conditions. It appears then that large amounts of copper (and zinc) are stored in the liver bound to metallothionein, and are mobilized as required for enzyme synthesis after birth. 

More recently, we have synthesized and studied the activity of 89, the first supported chiral catalyst for olefin metathesis (Scheme 20) [28]. Catalyst 89 efficiently promotes a range of ARCM and AROM processes a representative example is shown in Scheme 20. Rates of reaction are lower than observed with the corresponding monomeric complex, but similar levels of enantioselectivity are observed. Although 89 must be kept under rigorously dry and oxygen-free conditions, it can be recycled. Catalyst activity, however, is notably diminished by the third cycle. As the data and the figure in Scheme 20 show, the product solution obtained by filtration contains significantly lower levels of metal impu-... 

The a-diketone 1 (ca. 2.0 mmol) in dichloromethane (5 mL) was added to silica gel (5 g) in a 100-mL round-bottomed flask. The mixture was sonicated for 5 min after which the solvent was evaporated under reduced pressure. The coated silica gel, divided into six nearly equal portions, was then placed in Pyrex tubes (18 Xl80 mm). In the experiments under oxygen-free conditions the tubes were degassed by three freeze-pump-thaw cycles and sealed. The tubes were rotated and irradiated for 48 h with a 100-W high-pressure mercury lamp. The irradiated silica gel was collected. Acetone (20 mL) was added to the silica gel to extract... 

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