Magnesium oxide, molecular weight

The mixture is kept for 3 hours at 105°C after the oxide addition is complete. By this time, the pressure should become constant. The mixture is then cooled to 50°C and discharged into a nitrogen-filled botde. The catalyst is removed by absorbent (magnesium siUcate) treatment followed by filtration or solvent extraction with hexane. In the laboratory, solvent extraction is convenient and effective, since polyethers with a molecular weight above about 700 are insoluble in water. Equal volumes of polyether, water, and hexane are combined and shaken in a separatory funnel. The top layer (polyether and hexane) is stripped free of hexane and residual water. The hydroxyl number, water, unsaturation value, and residual catalyst are determined by standard titration methods. 

Similarly, carbon disulfide and propylene oxide reactions are cataly2ed by magnesium oxide to yield episulftdes (54), and by derivatives of diethyUiac to yield low molecular weight copolymers (55). Use of tertiary amines as catalysts under pressure produces propylene trithiocarbonate (56). 

In addition to the fluoroplastics and fluororubbers already described other fluoropolymers have been marketed. Polymers of hexafluoropropylene oxide are marketed by Du Pont (Krytox). These materials have a low molecular weight (2000-7000) and are either oils or greases. The oils are uses as lubricants, heat transfer fluids and non-flammable oils for diffusion pumps. The greases are also used as lubricants. They have good heat and oil resistance but it is said that explosions may result from contact with the surfaces aluminium or magnesium cuttings. 

Alternative to m-chloroperbenzoic acid.1 This oxidant has been introduced as a suitable replacement for m-chloroperbenzoic acid, which is no longer available from commercial sources because of hazards in the manufacture. Actually MMPP is a safer reagent than MCPBA, which is shock-sensitive and potentially explosive. MMPP is soluble in water and in low-molecular-weight alcohols. The by-product, magnesium phthalate, is water-soluble and easily removed. It is generally more stable than other percarboxylic acids. It can replace MCPBA for the usual classic oxidations epoxidation, Baeyer-Villiger reactions, and oxidation of amines to N-oxides. 

TABLE A2 Thermochemical Data of Selected Chemical Compounds Magnesium oxide (M3O), crystal-liquid, molecular weight = 40.3044... 

These reactions are often conducted in water, or in acetone-water mixtures for higher molecular weight amines.Magnesium sulfate is frequently used as an additive in these reactions to control solution pH. 1,3,5,7-Tetranitroadamantane (71) has been obtained via the permanganate oxidation of the hydrochloride salt of 1,3,5,7-tetraaminoadamantane (70) (Table 1.7). The 45 % yield for this reaction reflects a relative yield of 82 % for the oxidation of each of the four amino groups. 

For the higher molecular weight feedstocks such as liquefied petroleum gas (usually propane CjH8) and naphtha (q.v.), nickel catalysts with alkaline carriers or alkaline-free catalysts with magnesium oxide as additive can be used. Both types of catalyst are less active than the conventional nickel catalyst. Therefore, a less rapid decomposition of the hydrocarbons is achieved. At the same time, the reaction of water with any carbon formed is catalyzed. 

The old method of heating the calcium salts of formic and a second carboxylic acid for aldehyde formation has been modified by the use of a catalytic decomposition technique. By this scheme, the acid vapors are passed over thorium oxide, titanium oxide, or magnesium oxide at 300° or the acids are heated under pressure at 260° in the presence of titanium dioxide. In the latter procedure, non-volatile acids can be used. With aliphatic acids over titanium oxide, reaction occurs only when more than seven carbon atoms are present, the yields increasing with increase in the molecular weight (78-90%). Aromatic-acids having halo and phenolic groups are converted in high yields to aldehydes, e.g., salicylaldehyde (92%) and p-chlorobenzaldehyde (8S>%). Preparation of a thorium oxide catalyst has been described (cf. method 186). 

The thermal decarboxylation of a mixture of barium salts has been used to prepare unsymmetrical ketones the yields are not stated. The earlier procedure has been modified by carrying out the reaction in vacuo in an iron flask. Glass reaction vessels are inferior. In this manner, a large number of the high-molecular-weight methyl ketone s, C9, C,o, C,j-C , and C, are prepared in 54-67% yields. Cyclopentanone has been synthesized in 80% yield by distillation of adipic acid from barium hydroxide at 295°. In a study of metallic oxides and carbonates, magnesium oxide is preferred for the liquid-phase ketonization of stearic acid at 330-360° (95%). A convenient method for the preparation of dibenzyl ketone is the reaction of phenylacetic acid, acetic anhydride. 

Again, from the results of the first experiment the molecular weight of magnesium oxide may be found. Thus. 25 gm. of oxygen formed. 62 gm. z.e.. 2.5 +. 37) of magnesium oxide. Hence the proportion —... 

The molecular weight of magnesium oxide is 40 (/.a 24 + 16), which is in fair agreement with the above experimental determination. It is generally accepted that a molecule of magnesium oxide contains one atom each of oxygen and magnesium. 

The JP 2001 states that magnesium silicate contains not less than 45.0% of silicon dioxide (SiOi molecular weight 60.08) and not less than 20.0% of magnesium oxide (MgO 40.30), and the ratio of percentage (%) of magnesium oxide to silicon dioxide is not less than 2.2 and not more than 2.5. 

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