Observations of the Thermal Decomposition of Brucite

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100101980 ◽

1968 ◽

Vol 26 ◽

pp. 446-447

Author(s):

P. L. Burnett ◽

W. R. Mitchell ◽

C. L. Houck

Keyword(s):

Thermal Decomposition ◽

Magnesium Oxide ◽

Basal Plane ◽

Magnesium Ions ◽

A Value ◽

Reaction Proceeds

Natural Brucite (Mg(OH)2) decomposes on heating to form magnesium oxide (MgO) having its cubic ﹛110﹜ and ﹛111﹜ planes respectively parallel to the prism and basal planes of the hexagonal brucite lattice. Although the crystal-lographic relation between the parent brucite crystal and the resulting mag-nesium oxide crystallites is well known, the exact mechanism by which the reaction proceeds is still a matter of controversy. Goodman described the decomposition as an initial shrinkage in the brucite basal plane allowing magnesium ions to shift their original sites to the required magnesium oxide positions followed by a collapse of the planes along the original <0001> direction of the brucite crystal. He noted that the (110) diffraction spots of brucite immediately shifted to the positions required for the (220) reflections of magnesium oxide. Gordon observed separate diffraction spots for the (110) brucite and (220) magnesium oxide planes. The positions of the (110) and (100) brucite never changed but only diminished in intensity while the (220) planes of magnesium shifted from a value larger than the listed ASTM d spacing to the predicted value as the decomposition progressed.

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Chlorination of Natural Rubber Solutions by Means of Phenyl Iododichloride

Rubber Chemistry and Technology ◽

10.5254/1.3542821 ◽

1955 ◽

Vol 28 (2) ◽

pp. 598-605 ◽

Cited By ~ 1

Author(s):

C. S. Ramakrishnan ◽

D. Raghunath ◽

J. B. Pande

Keyword(s):

Thermal Decomposition ◽

Carbon Tetrachloride ◽

Natural Rubber ◽

Hydrogen Chloride ◽

Atmospheric Oxygen ◽

A Value ◽

Reaction Proceeds ◽

Chlorine Radicals ◽

Slight Amount ◽

Additive Reaction

Abstract The loss of unsaturation attending the chlorination of carbon tetrachloride solutions of unmasticated pale crepe and deproteinized rubbers by means of phenyl iododichloride was followed by quantitative ozonization of the chlorinated products, ranging in chlorine contents from 2.3 to 73.6 per cent. It is concluded from such studies that the reaction proceeds mainly by the additive reaction of the chlorine radicals produced by the thermal decomposition of phenyl iododichloride. The hydrogen chloride found in the preparation of these chlorinated products was determined. It has a value below 1 per cent up to about 15 per cent chlorine content and thereafter it increases. However, this value generally does not exceed 4 per cent. This indicates the occurrence of only a slight amount of substitutive reaction by chlorine. Cyclization also takes place, probably following an additive reaction of the chlorine radicals. The main difference between the deproteinized rubber and pale crepe rubber reactions is confined to the very early stages, wherein the nonrubber components have a directive influence in bringing about a slightly earlier onset of cyclization. It is also concluded that atmospheric oxygen has a negligible effect on the reaction.

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A synthesis and some reactions of 7-Oxabicyclo[2.2.1]heptan-2-one

Australian Journal of Chemistry ◽

10.1071/ch9832473 ◽

1983 ◽

Vol 36 (12) ◽

pp. 2473 ◽

Cited By ~ 17

Author(s):

J Moursounidis ◽

D Wege

Keyword(s):

Thermal Decomposition ◽

Alder Reaction ◽

Diels Alder ◽

Acid Mixture ◽

Diels Alder Reaction ◽

Reaction Proceeds ◽

Atom Migration ◽

Acyl Azide ◽

Mild Hydrolysis ◽

Hydrolysis Of

Diels-Alder reaction between furan and α-chloroacrylonitrile gives a mixture of exo-2-chloro-and endo-2-chloro-7-oxabicyclo[2.2.1]hept-5-ene-2-carbonitrile (4) and (5). Mild hydrolysis affords the corresponding α-chloro acid mixture, from which the endo carboxylic acid may be removed through iodo lactone formation. Catalytic hydrogenation of (4) and (5) followed by hydrolysis, acyl azide formation, Curtius rearrangement, and hydrolysis of the resulting mixture of a-chloro isocyanates yields 7-oxabicyclo[2.2.l]heptan-2-one (1) in preparatively useful amounts. Reduction of (1) gives only endo alcohol, and Baeyer-Villiger reaction proceeds with exclusive bridgehead atom migration. Thermal decomposition of the sodium salt of the p-toluenesulfonylhydrazone of (1) affords 7-oxatricyclo[2.2.1 .02,6]heptane.

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The thermal decomposition of nitrogen pentoxide at low pressures

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

10.1098/rspa.1925.0142 ◽

1925 ◽

Vol 109 (751) ◽

pp. 526-540 ◽

Cited By ~ 5

Keyword(s):

Thermal Decomposition ◽

The Other ◽

Nitrogen Tetroxide ◽

Nitrogen Pentoxide ◽

Other Hand ◽

Rate Of Reaction ◽

Reaction Proceeds ◽

Products Of Reaction ◽

Glass Surfaces ◽

Low Pressures

Unimolecular reactions possess a unique interest in that, as Perrin (‘Ann. Physique,’ vol. 11, p. 5, 1919) first pointed out, for the occurrence of such, some type of interaction between radiation and matter must take place. Although such reactions appear to be extremely rare, many physical processes such as evaporation, ionisation in gases at high temperatures and radio-active decay, proceed at rates conforming to a unimolecular law; true chemical reactions which are definitely unimolecular and not pseudo-unimolecular in character are, on the other hand, stated by many ( e. g ., Lowry, ‘Trans. Farad. Soc.,’ vol. 17, p. 596 (1922) ) to be non-existent. In order to substantiate this statement, it is clearly necessary to prove the more complex character of any reaction which satisfies the usual criteria of unimolecular change. The thermal decomposition of gaseous nitrogen pentoxide apparently fulfils these conditions, for Daniels and Johnston (‘J. Am. C. S.,’ vol. 43, p. 53 (1921)) showed that the reaction proceeded according to a unimolecular law over wide ranges of variation of pressure, and Lueck ( ibid ., vol. 44, p. 757 (1922)) obtained practically identical unimolecular constants for the decomposition in solution in carbon tetrachloride and chloroform. On the other hand, Daniels, Wulf and Karrer ( ibid ., vol. 44, p. 2402 (1922) ) suspected the reaction to be autocatalytic, owing to the apparent retardation of the reaction velocity in the presence of ozone, but the experiments of one of us (Hirst, ‘J. C. S.,’ vol. 127, p. 657 (1925), and of White and Tolman (‘J. Am. C. S.’ vol. 47, p. 1,240 (1925)) proved this to be erroneous. In addition, it has been shown that the reaction proceeds uniformly according to the unimolecular law even in the presence of extensive glass surfaces, or of gases which may be either indifferent, such as argon and nitrogen, or the products of reaction, such as nitrogen tetroxide or dioxide or oxygen. The rate of reaction may be expressed in the form - d C/ dt = 4·98 × 10 13 e -24.700/RT . C. Attempts have been made to interpret the experimental results on the hypothesis that the reaction is in reality bimolecular, and only apparently unimolecular in character; but owing to the abnormally large value of the energy of activation, namely, 24,700 calories per gram. molecule, the number of molecules which could be activated per second by inelastic collision, calculated according to the kinetic theory, falls far short of the observed reaction rate, being, in fact, some 10 5 times smaller.

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Study on the Direct Oxidation Thermal Decomposition of Magnesium Chloride by Product in the Sponge Titanium Production Process to Prepare Magnesium Oxide

The Minerals, Metals & Materials Series - Magnesium Technology 2017 ◽

10.1007/978-3-319-52392-7_32 ◽

2017 ◽

pp. 209-213

Author(s):

Liping Niu ◽

Ting-an Zhang ◽

Guozhi Lv ◽

Baojing Zhang

Keyword(s):

Thermal Decomposition ◽

Production Process ◽

Magnesium Oxide ◽

Magnesium Chloride ◽

Direct Oxidation ◽

Sponge Titanium

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Doxorubicin Loaded Magnesium Oxide Nanoflakes as pH Dependent Carriers for Simultaneous Treatment of Cancer and Hypomagnesemia

Nanomaterials ◽

10.3390/nano9020208 ◽

2019 ◽

Vol 9 (2) ◽

pp. 208 ◽

Cited By ~ 7

Author(s):

Tharindu Ranathunge ◽

D.G.G.P. Karunaratne ◽

R.M.G. Rajapakse ◽

Davita Watkins

Keyword(s):

Magnesium Oxide ◽

Drug Loading ◽

Dual Therapy ◽

Drug Carriers ◽

Magnesium Ions ◽

Simultaneous Treatment ◽

Mgo Nanoparticles ◽

Acidic Conditions ◽

Ph Dependent ◽

Cytotoxicity Effects

Doxorubicin (DOX) is an anticancer drug commonly used in treating cancer; however, it has severe cytotoxicity effects. To overcome both the adverse effects of the drug and mineral deficiency (i.e., hypomagnesemia) experienced by cancer patients, we have developed magnesium oxide (MgO) nanoflakes as drug carriers and loaded them with DOX for use as a targeted drug delivery (TDD) system for potential application in cancer therapy. The synthesis employed herein affords pure, highly porous MgO nanoparticles that are void of the potentially harmful metal contaminants often discussed in the literature. Purposed for dual therapy, the nanoparticles exhibit an impressive 90% drug loading capacity with pH dependent drug releasing rates of 10% at pH 7.2, 50.5% at pH 5.0, and 90.2% at pH 3. Results indicate that therapy is achievable via slow diffusion where MgO nanoflakes degrade (i.e., dissolve) under acidic conditions releasing the drug and magnesium ions to the cancerous region. The TDD system therefore minimizes cytotoxicity to healthy cells while supplying magnesium ions to overcome hypomagnesemia.

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The decomposition of magnesium hydroxide in an electron microscope

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1958.0188 ◽

1958 ◽

Vol 247 (1250) ◽

pp. 346-352 ◽

Cited By ~ 72

Keyword(s):

Electron Beam ◽

Electron Microscope ◽

Electron Diffraction ◽

Single Crystals ◽

Magnesium Oxide ◽

Magnesium Hydroxide ◽

Basal Plane ◽

Morphological Changes ◽

Water Molecules ◽

Two Stages

The beam of an electron microscope has been used to dehydrate single crystals of magnesium hydroxide to magnesium oxide. Electron diffraction photographs and electron micrographs were taken at various stages to follow the crystallographic and morphological changes which accompany decomposition. The decomposition may be considered to occur in two stages. First, there is a small shrinkage in the basal plane, and the resulting strain causes a maze of cracks in the crystal. This change is followed by a collapse of the planes down the original [0001] of magnesium hydroxide. The collapse is controlled by the migration of water molecules from between the planes to a surface where they can escape. The product is a highly oriented aggregate of micro-crystallites of magnesium oxide. More intense irradiation in the electron beam occasionally causes bulk movement of the solid.

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The thermal decomposition of n-propyl bromide

Australian Journal of Chemistry ◽

10.1071/ch9680973 ◽

1968 ◽

Vol 21 (4) ◽

pp. 973 ◽

Cited By ~ 5

Author(s):

JTD Cross ◽

VR Stimson

Keyword(s):

Thermal Decomposition ◽

Rate Constant ◽

Hydrogen Bromide ◽

Bromine Atom ◽

Order Reaction ◽

Chain Mechanism ◽

Initial Concentration ◽

First Order ◽

Reaction Proceeds ◽

Atom Chain

Mechanisms already proposed or formally possible for the decomposition of n-propyl bromide as a 312-order reaction are shown to be unsatisfactory, and the reaction has been reinvestigated. Two reactions occur simultaneously: (a) a first-order reaction identifiable with the maximally inhibited reaction and presumably molecular; (b) a reaction second order in the initial concentration and somewhat autocatalysed as the reaction proceeds. The rate constant is given by k2 == 1018.1exp(-49300/RT)sec-1ml mole-1 Reaction (b) is catalysed by hydrogen bromide and inhibited by propene, and a bromine atom chain mechanism with hydrogen bromide catalysed initiation is proposed. Bromine-catalysed decomposition has also been studied. The mechanism of the inhibition is discussed.

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Síntese de éster de cadeia longa via catálise básica heterogênea (Synthesis of long chain ester by heterogeneous base catalysis)

Eclética Química Journal ◽

10.26850/1678-4618eqj.v34.2.2009.p49-57 ◽

2018 ◽

Vol 34 (2) ◽

pp. 49

Author(s):

Dorsan Dos Santos Moraes ◽

G. N. R. Filho ◽

José Roberto Zamian

Keyword(s):

Thermal Decomposition ◽

Magnesium Oxide ◽

Structural Properties ◽

Methyl Palmitate ◽

Base Catalysis ◽

Chain Alcohol ◽

Long Chain Alcohol ◽

Heterogeneous Base ◽

Long Chain ◽

Chain Ester

A long chain ester was prepared by transesterification of methyl palmitate with long chain alcohol using magnesium oxide as catalyst prepared by thermal decomposition of different precursors with the intention of establish relations among structural properties and activities. Temperature and catalyst amounts were modified in order to evaluate the yield of the ester in function the precursors used in preparation of the oxide.

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Osmotic and Ionic Regulation in a Terrestrial Snail, Pomatias Elegans (Gastropoda, Prosobranchia) With a Note on Some Tropical Pomatiasidae

Journal of Experimental Biology ◽

10.1242/jeb.57.1.205 ◽

1972 ◽

Vol 57 (1) ◽

pp. 205-215

Author(s):

T. J. RUMSEY

Keyword(s):

Ionic Composition ◽

Calcareous Soils ◽

Buffering Capacity ◽

Magnesium Ions ◽

Bicarbonate Concentration ◽

Yearly Cycle ◽

Mantle Fluid ◽

A Value ◽

Calcium And Magnesium ◽

Calcium And Magnesium Ions

1. The haemolymph concentration in the pomatiasids is higher than in any other terrestrial gastropods so far studied. 2. P. elegans shows a yearly cycle of haemolymph concentration, showing maximum values in January and February 1971, and June and July 1971. Minimal values were obtained between March and May 1971. 3. The concentration of calcium in the haemolymph (especially of Pomatias) is high, a value of 20.2 mM/l being obtained for one group of Pomatias. This reflects their dependence on calcareous soils for survival. 4. Haemolymph and urine are isosmotic and isoionic. 5. The mantle fluid is generally less concentrated than the haemolymph and urine, ionic reabsorption presumably occurring over the mantle epithelium. Potassium, calcium and magnesium ions are selectively reabsorbed. 6. The highest haemolymph concentrations in pomatiasids were found in animals that inhabited areas with the least rainfall, and vice versa. 7. During inactivity the percentage ionic composition of the haemolymph of P. elegans altered as the O.P. increased. Sodium decreased, magnesium increased, and bicarbonate decreased. It is suggested that the fall in bicarbonate concentration is due to a change in the buffering capacity of the haemolymph.

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