Dehydration sodium hydroxide effects

Ring D inversion seems to be a crucial step in biogenetic transformations of protoberberines to related alkaloids such as rhoeadine, retroprotoberberine, spirobenzylisoquinoline, and indenobenzazepine alkaloids. 8,14-Cyclober-bin-13-ol 478 derived from berberine (15) was successively treated with ethyl chloroformate, silver nitrate, and pyridinium dichromate (PDC) in dimethyl-formamide to give the keto oxazolidinone 479 (Scheme 98). Heating of 479 with 10% aqueous sodium hydroxide in ethanol effected hydrolysis, retro-aldol reaction, cyclization, and dehydration to provide successfully the... 

Methyl alcohol of very high purity can be obtained by fractional distillation using a column of 1-3 metres effective length and then refluxing with aluminium amalgam. It is then refluxed under a column packed with dehydrated copper sulphate, to remove ammonia. A sensitive test for acetone and formaldehyde is the addition of cone, mercuric cyanide solution, in 6N-sodium hydroxide. A white precipitate indicates ketone if it darkens on standing aldehyde is also present. (J. C. S., 127, 2552.)... 

Alumina has found wide application in GSC. It is a highly polar material with a typical surface area of 250 m g . It interacts strongly with polar molecules such as water, and also has some catalytic activity, for example, it may convert acetone to diacetone alcohol or dehydration may occur. Much of the early work on alumina was carried out by Scott who subsequently concentrated his research on surface modified materials [37,38]. He measured polarity in terms of the retention of ethylene relative to non-polar ethane and propane. Activation by heating at temperatures up to 500°C increased the polarity by loss of water and adsorption of water reduced polarity until a minimum was reached when the amount required for a monolayer had been adsorbed. Further water continued to reduce the activity (by reducing the surface area) but increased the polarity [39-41]. Scott later extended his work on alumina to substances modified with sodium hydroxide and obtained results similar to those obtained for the water-modified alumina without the need to presaturate the carrier gas. Retention of benzene relative to heptane increased markedly on alumina modified with sodium salts in the order OH > Cl > Br > I . A recent comparative study of the modifier effects alkali... 

In our experience, in addition to moisture, commercial methanol may also contain of organic impurities such as acetone, formaldehyde, ethanol, methyl formate and even acetaldehyde. The water content can be reduced to less than 0.01% by fractional distillation. Further drying may be effected with calcium hydride or calcium sulphate, but most efficiently with metallic sodium. Experiments in this laboratory showed that treatment with sodium, twice repeated, decreased the water content to S x 10 %. If a larger amount of acetone is present as an impurity, it can be precipitated first in the form of iodoform, by treatment with iodine and sodium hydroxide. Methanol is then distilled off from the precipitate, and the dehydration process is performed afterwards. 

To the percolate add 30 ml of N sulphuric acid, or sufficient to render the mixture faintly acid, shake well, allow to separate and run off the lower layer. Continue the extraction with 10-ml portions of 0-lN sulphuric acid until extraction of the alkaloids is complete, as shown by the iodine test. Wash the mixed acid solutions with about 10 ml of chloroform and run off the latter into a second separator containing 20 ml of 0 1 N sulphuric acid, shake, allow to separate and reject the chloroform. Repeat the washing of the liquid in the first separator with two further 5-ml quantities of chloroform, transfer each in turn to the second separator, wash with the same aqueous acid liquid, allow to separate and reject the chloroform layer as before. Transfer the acid liquid from the second separator to the first separator, make just alkaline with dilute ammonia solution and add 2 ml in excess shake with successive portions of chloroform until complete extraction of the alkaloids is effected, washing each chloroform extract with the same 20 ml of water contained in another separator. Remove the chloroform by distillation, add to the residue 2 ml of dehydrated ethanol, evaporate at a temperature not exceeding 60, and dry at a temperature below 60for thirty minutes. Dissolve the residue in 2 ml of neutral 95 per cent ethanol, warm until dissolved, add 20 ml of 0 02N sulphuric acid and 10 ml of water cool and titrate with 0-02N sodium hydroxide, using methyl red as indicator. 1 ml of 0-02N acid = 0-01291 g of the alkaloids of aconite calculated as aconitine. 

These thermal effects associated to the hydrolysis reaction have been studied on a fully dehydrated NaBH4 powder by means of an IR imaging camera and a differential titration calorimeter. Various amounts of solid sodium hydroxide were added to the system (NaBH4 -I- metallic nanoCobalt catalyst) allowing an increase of the maximum reaction temperature (up to 140 °C). The reaction maximum temperature and the hydrogen yield were considerably modified by varying the amount of NaOH and the amount of catalyst (Fig. 11.13). At a temperature of more than 140 °C, it is reasonable to expect the formation of low hydration borate phases. In fact, at temperatures above 105 °C water is expected to participate preferentially in the hydrolysis reaction rather than in the hydration of the... 

Some of the gas dissolves in the aqueous solution, and the gas pressure developed within the apparatus forces the mixture out through the nozzle, which is directed onto the flame. If some heavy molasses or similar gluelike material is added to the sodium carbonate solution and some aluminum sulfate is added to the sulfuric acid, the solution discharges from the nozzle in the form of a foam in which the carbon dioxide gas is trapped. This heavy blanket of foam containing carbon dioxide settles over and around the burning object. The aluminum sulfate hydrolyzes to form aluminum hydroxide, which, at the temperature of the flame, dehydrates to produce a crust of aluminum oxide over the flame. Both effects serve to extinguish the flame. The common Foamite fire extinguisher is an example of this type. 

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