Reaction methods inert atmosphere

Three operations usually accompany the carrying out of a reaction on a synthetic scale stirring, addition of a reagent, and temperature control. Most often, a threenecked round-bottom flask allows simultaneous execution of these operations along with certain other controls that may be desirable, such as introduction of an inert atmosphere or maintenance of reflux. In what follows, a short description of a suitable method of carrying out each of the operations is given. 

For very high melting polymers (Tm > 300°C), a solution polymerization is normally employed. If this is started from the reactive acid chloride, the reaction temperature can be low. Polymers from acid chlorides can also be prepared by the interfacial method. Semicrystalline PA can be postcondensed in the solid state to higher molecular weights. To do this, the polymer powder/particles are heated for many hours below their melting temperature in an inert atmosphere. 

Decomposition of diazo compounds by iron porphyrins is a convenient method for the synthesis of non-heteroatom carbene-iron porphyrins [22]. Reaction of [Fe(F2o-TPP)] [F20-TPP = meso-tetrakis(pentafluorophenyl)porphyrinato dianion] with diazo compounds N2C(Ph)R (R = Ph, C02Et, C02CH2CH=CH2) under an inert atmosphere afforded complexes [Fe(F2o-TPP)C(Ph)R] in 65-70% yields (Scheme 2). Like the halocarbene complex [Fe(TPP)(CCl2)], [Fe(F2o-TPP)CPh2] reacted with Melm to afford six-coordinate species [(MeIm)Fe(F2o-TPP)CPh2] in 65% isolated yield. 

Measuring the relative oxidative stability of polymers is important. Measurements can be used to determine dependencies on structural and molecular weight/weight distribution or the effectiveness of an antioxidant, or to perhaps assess the amount present in a polymer sample, etc. The preferred and commonest method consists in raising the sample temperature to a predetermined level, while in an inert atmosphere, then switching the atmosphere to air or oxygen. The time to the onset of exothermic reaction is measured. 

This method, specific for the epoxidation of allylic alcohols, gives good results if the reaction is carried out under strictly anhydrous conditions, otherwise the yield or the enantiomeric excess can decrease, sometimes dramatically. This can explain the small differences between the results obtained during the validation experiments and the published results. All the different reagents are commercially available they can be used as received but in case of low yield and/or enantiomeric excess they should be distilled and dried under an inert atmosphere. Table 5.1 gives some other examples of substrates which can be epoxidized using the procedure described above. 

Half-blocked Dllsocyanates. The half-blocked diisocyanates were prepared using conventional methods (2) by adding dropwlse, over a period of one hour, 1 mole of alcohol to 1 mole of diisocyanate and 100 mg dibutyl tin dilaurate in methyl amyl ketone under an inert atmosphere. After the addition of the alcohol, the reaction was heated at 60-80°C for 2 hours. For half-blocked diisocyanates prepared from tertiary alcohols, the heating period was replaced with room temperature stirring for 24-36 hours to prevent undesirable side reactions. 

The reaction, which is very exothermic, is carried out at 700-800 °C in a steel bomb under an inert atmosphere. The method, which requires very careful control of the temperature, is capable of yielding titanium with a purity of 99.9%. It is also possible to prepare the metal by hydrogen reduction6 of the tetrachloride at approximately 2000 °C (equation 3). The difficulties of removing hydrogen from the metal, and the high temperatures required, make the method impracticable industrially. 

Electrochemical techniques are the most widely used methods to obtain nickel(III) complexes. Generally the oxidation of the nickel(II) complexes is performed in acetonitrile solutions under an inert atmosphere using a platinum electrode.3052 A tetraalkylammonium salt, usually the perchlorate, is employed as supporting electrolyte (ca. 0.1 M). The complete procedure is often carried out in the dark at ca. 5°C to prevent possible photoreduction reactions.3053-3055... 

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