Periodic acid acids

Ozone is formed in certain chemical reactions, including the action of fluorine on water (p. 323) and the thermal decomposition ofiodic(VII) (periodic) acid. It is also formed when dilute (about 1 M) sulphuric acid is electrolysed at high current density at low temperatures the oxygen evolved at the anode can contain as much as 30% ozone. 

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 ... 

The "periodic acids and periodates are powerful oxidising agents and they will oxidise manganese to manganate(VlI). a reaction used to determine small quantities of manganese in steel. 

The pinacol hydrate may be used (i) for conversion to pina-colone (see below), and (ii) to illustrate the oxidation of 1,2-diols to aldehydes or ketones by periodic acid (p. 145),... 

Add 1 drop (0 05 ml.) of concentrated nitric acid to 2 0 ml. of a 0 5 per cent, aqueous solution of paraperiodic acid (HjIO,) contained in a small test-tube and shake well. Then introduce 1 op or a small crystal of the compound. Shake the mixture for 15 seconds and add 1-2 drops of 5 per cent, aqueous silver nitrate. The immediate production of a white precipitate (silver iodate) constitutes a positive test and indicates that the organic compound has been oxidised by the periodic acid. The test is based upon the fact that silver iodate is sparingly soluble in dilute nitric acid whereas silver periodate is very soluble if too much nitric acid is present, the silver iodate will not precipitate. 

An alternative procedure for the above test is as follows. Mix 2-3 ml. of 2 per cent, aqueous paraperiodic acid solution with 1 drop of dilute sulphuric acid (ca. 2 5N) and add 20-30 mg. of the compound. Shake the mixture for 5 minutes, and then pass sulphur dioxide through the solution until it acquires a pale yellow colour (to remove the excess of periodic acid and also iodic acid formed in the reaction). Add 1-2 ml. of Schiff s reagent (Section 111,70) the production of a violet colour constitutes a positive test. 

The polyhydric alcohols of Solubility Group II are liquids of relatively high boiling point and may be detected inter alia by the reactions already described for Alcohols (see 6). Compounds containing two hydroxyl groups attached to adjacent carbon atoms (1 2-glyeols), a-hydroxy aldehydes and ketones, and 1 2-diketones may be identified by the periodic acid test, given in reaction 9. 

Periodic acid has a selective oxidising action upon compounds having two hydroxyl groups or a hydroxyl and an amino group attached to adjacent carbon atoms and is characterised by the cleavage of the carbon - carbon bond (Malaprade reaction) ... 

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

Place 2 ml. of the periodic acid reagent in a small test tube, add one drop (no more—otherwise the silver iodate, if formed, will fail to precipitate) of concentrated nitric acid, and shake well. Add one drop or a small crystal of the compound to be tested, shake the mixture for 15-20 seconds, and then add 1-2 drops of 3 per cent, silver nitrate solution. The instantaneous formation of a white precipitate of silver iodate is a positive test. Failure to form a precipitate, or the appearance of a brown precipitate which redissolves on shaking, constitutes a negative test. 

A reaction characteristic of vicinal diols is their oxidative cleavage on treatment with periodic acid (HIO4) The carbon-carbon bond of the vicinal diol unit is broken and two carbonyl groups result Periodic acid is reduced to iodic acid (HIO3)... 

Can you remember what re action of an alkene would give the same products as the periodic acid cleavage shown here" ... 

Cyclic diols give dicarbonyl compounds The reactions are faster when the hydroxyl groups are cis than when they are trans but both stereoisomers are oxidized by periodic acid... 

Periodic acid cleavage of vicinal diols is often used for analytical purposes as an aid m structure determination By identifying the carbonyl compounds produced the con stitution of the starting diol may be deduced This technique finds its widest application with carbohydrates and will be discussed more fully in Chapter 25... 

Section 15 12 Periodic acid cleaves vicinal diols two aldehydes two ketones or an aldehyde and a ketone are formed... 

A diol (CgHig02) does not react with periodic acid Its H NMR spectrum contains three singlets at 8 1 2 (12 protons) 1 6 (4 protons) and 2 0 (2 protons) What is the structure of this dioH... 

Periodic acid oxidation (Section 15 12) finds extensive use as an analytical method m carbohydrate chemistry Structural information is obtained by measuring the number of equivalents of periodic acid that react with a given compound and by identifying the reaction products A vicinal diol consumes one equivalent of penodate and is cleaved to two carbonyl compounds... 

Only one site for periodic acid cleavage in methyl a D arabmofuranoside... 

CEBSSS Give the products of periodic acid oxidation of each of the fol lowing How many moles of reagent will be consumed per mole of substrate in... 

D Arabinose showing points of cleavage by periodic acid each cleavage requires one equivalent of FIIO4... 

Vicinal diol and a hydroxy carbonyl functions in carbohydrates are cleaved by periodic acid Used analytically as a tool for structure determination... 

HIO4 periodic acid H2S2O3 thiosulfuric acid... 

Dimethylsulfoxide Acyl and aryl halides, boron compounds, bromomethane, nitrogen dioxide, magnesium perchlorate, periodic acid, silver difluoride, sodium hydride, sulfur trioxide... 

Oxidation of a glycol can lead to a variety of products. Periodic acid quantitatively cleaves 1,2-glycols to aldehydes and is used as an analysis method for glycols (12,13). The oxidation of propylene glycol over Pd/C modified with Pb, Bi, or Te forms a mixture of lactic acid, hydroxyacetone, and pymvic acid (14). Air oxidation of propylene glycol using an electrolytic crystalline silver catalyst yields pymvic aldehyde. 

The presence of manganese can be detected by formation of the purple MnO upon oxidation using bismuth or periodate in acidic solution. A very sensitive test is the reaction of and formaldoxime hydrochloride in aqueous alkaline solution, which also leads to the production of a purple MnO ... 

Molded polyamide surfaces can be hardened by grafting with Ai,Ai-diallylacrylamide [3085-68-5] monomer under exposure to electron beam (159). AijAZ-DiaHyltartardiamide [58477-85-3] is a cross-linking agent for acrylamide reversible gels in electrophoresis. Such gels can be dissolved by a dilute periodic acid solution in order to recover protein fractions. 

The oxidation of 4-bromophenols to quinones can also be accompHshed using periodic acid (113). A detailed study of this reagent with stericaHy hindered phenols provided insight about the quinonoid product (114). The highest yield of 2,6-di-/-butyl-l,4-ben2oquinone [719-22-2] is for the case of R = OCH. The stilbene stmcture [2411-18-9] is obtained in highest yield for R = H. 

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