Periodic acids preparation

Of the older methods for the preparation of periodic acid, the most satisfactory for obtaining large quantities is the electrolytic oxidation of iodic acid at an anode of platinum plated with lead dioxide, the cathode solution being dilute nitric acid.1 The iodic acid for this preparation is conveniently prepared by the electrolytic oxidation of iodine.1 However, periodic acid prepared in this way often contains... 

Preparation of ah Aqueous Solution of Periodic Acid. Aqueous solutions of periodic acid prepared from commercial paraperiodic add frequently deposit a small predpitate upon standing at room temperature. 

Preparation of ah Aqueous Solution of Periodic Acid. Aqueous solutions of periodic acid prepared from commercial parapeiiodic add frequently deposit a small predpitate upon standing at room temperature. If this occurs, the solution should be kept for twenty-foiu hours and filtered before analyds and use in oxidation experiments. When this procedure is followed, a concentration near 0.64 M is usually found by analysis for a solution prepared with 124.5 g. of crystalline paraperiodic add per liter of solution at 20°. 

Periodic acid Prepare 10 mM periodic acid by dissolving 22.8 mg in 10 ml distilled water. Prepare fresh (for total sugar stain). Selective staining of sialic acid residues can be achieved by using a 1 mM periodic acid solution (Gershoni et al., 1985). 

The existence of chloric(VII) (perchloric) and iodic(VII) (periodic) acids has long been known but bromic(VII) acid has only recently been prepared. 

These are acids which can be regarded, in respect of their formulae (but not their properties) as hydrates of the hypothetical diiodine heptoxide, liO-j. The acid commonly called periodic acid , I2O7. 5H2O, is written HglO (since the acid is pentabasic) and should strictly be called hexaoxoiodic(VII) acid. It is a weak acid and its salts are hydrolysed in solution. It can be prepared by electrolytic oxidation of iodic(V) acid at low temperatures ... 

Y-Phenylbutyric acid. Prepare amalgamated zinc from 120 g. of zinc wool contained in a 1-litre rovmd-bottomed flask (Section 111,50, IS), decant the liquid as completely as possible, and add in the following order 75 ml. of water, 180 ml. of concentrated hydrochloric acid, 100 ml. of pure toluene (1) and 50 g. of p benzoylpropionic acid. Fit the flask with a reflux condenser connected to a gas absorption device (Fig. II, 8, l,c), and boil the reaction mixture vigorously for 30 hours add three or four 50 ml. portions of concentrated hydrochloric acid at approximately six hour intervals during the refluxing period in order to maintain the concentration of the acid. Allow to cool to room temperature and separate the two layers. Dilute the aqueous portion with about 200 ml. of water and extract with three 75 ml. portions of ether. Combine the toluene layer with the ether extracts, wash with water, and dry over anhydrous magnesium or calcium sulphate. Remove the solvents by distillation under diminished pressure on a water bath (compare Fig. II, 37, 1), transfer the residue to a Claisen flask, and distil imder reduced pressure (Fig. II, 19, 1). Collect the y-phenylbutyric acid at 178-181°/19 mm. this solidifies on coohng to a colourless sohd (40 g.) and melts at 47-48°. 

The periodic acid reagent is prepared by dissolving 1 - 0 g. of paraperiodic acid HglOg in 200 ml. of distilled water. 

For light microscopic examination, liver tissue was fixed in 10 % buffered formalin, embedded in paraffin, sectioned and stained with hematoxylin and eosin. In some cases, preparations were stained with PTAH (phosphotungstic acid-haematoxylin), by the Van Gieson method and the PAS (periodic acid-Schiff)... 

During the preparation of the quaternary oxidant tetraethylammonium iodate from the aqueous reagents, the residue after vacuum evaporation of most of the water exploded, breaking the flask. This was attributed to possible presence of excess periodic acid in the reaction mixture [1]. Further details and precautions to avoid heating the salt, normally stable in storage, are given [2],... 

An aqueous solution of periodic acid, free from metal ions, may be prepared through the conversion of potassium metaperiodate to the slightly soluble barium dimesoperiodate, Ba2l207, which, through reaction with an equivalent amount of sulfuric acid, yields pure periodic acid.107 Hudson found that nitrate as an impurity in periodic acid gives rise to erroneous results in this field.239 ... 

In homogeneous reactions, the upper limits of concentration are determined by the (limited) solubility of the salts of periodic acid and by the low pH values produced by periodic acid itself. Apart from these considerations, the concentration conditions to be selected are governed by the type of information desired. A very dilute solution having a high oxidant substrate ratio is used in the exploratory or preliminary phase defined earlier (see p. 13), but a more concentrated solution, in which the oxidant is only slightly in excess of the theoretical, is recommended for the preparative phase. 

Other Methods of Preparation.—Ethyl 2-formyl-5-methyl-4-furoate has also been prepared by the oxidation of ethyl 2-(D-ara6ino-tetrahydroxybutyl)-5-methyl-4-furoate by means of periodic acid,8 sodium periodate,19 or minium ( red lead ) in acetic acid.66 It can also be prepared by the oxidation with sodium periodate of ethyl 2-(D-lyzo-tetrahydroxybutyl)-5-methyl-4-furoate,15 of ethyl 2-(D-fftreo-trihydroxy-propyl)-5-methyl-4-furoate,13 of ethyl 2-(o-erythro-trihydroxypropyl)-5-methyl-4-furoate,17 of ethyl 2-(L-eryfAro-trihydroxypropyl)-5-methyl-4-furoate,13 and of ethyl 2-(D-goIado-pentahydroxypentyl)-5-methyl-4-furoate.16... 

It is convenient to prepare the solution of periodic acid the day before, and then to decant it from some undissolved particles which nearly always remain. A small excess of periodic acid is not detrimental. 

The peptide/polypeptide product is usually hydrolysed by incubation with 6 mol l-1 HC1 at elevated temperatures (110 °C), under vacuum, for extended periods (12-24 h). The constituent amino acids are separated from each other by ion-exchange chromatography and identified by comparison with standard amino acid preparations. Reaction with ninhydrin allows subsequent quantification of each amino acid present. 

Quaternary ammonium periodates, prepared either from periodic acid and the quaternary ammonium hydroxide [21, 22] or by metathesis from sodium periodate and a quaternary ammonium salt [e.g. 23-25], have been used for a range of oxidations at stoichiometric levels in two-phase systems [21-33], The tetra-n-butyl-ammonium and hexadecyltrimethylammonium salts are both highly soluble in organic solvents (considerably less so in water), whereas benzyltriethylammonium periodate has a lower solubility and stability than either salt. 

The acids prepared by the alcoholysis of phosphorus(V) sulfide are frequently unstable to oxidative-hydrolytic action of the atmosphere thus, immediate conversion of the acids to metal complexes is recommended. The acids can be stored under nitrogen for reasonable periods of time without extensive de-... 

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