Diol , vicinal

Diols, meso-, enzymic oxidation to y-lactones, 63, 14 DIOLS, VICINAL, EPOXIDES FROM, 63, 140 m-D1oxane, 2-(2-bromoethyD- [33884-43-4], 62, 148... 

Vicinal diols are diols that have their hydroxyl groups on adjacent carbons Two commonly encountered vicinal diols are 1 2 ethanediol and 1 2 propanediol... 

In the laboratory vicinal diols are normally prepared from alkenes using the reagent osmium tetraoxide (OSO4) Osmium tetraoxide reacts rapidly with alkenes to give cyclic osmate esters... 

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)... 

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... 

Reaction is acid catalyzed Equilibrium constant normally favorable for aide hydes unfavorable for ketones Cyclic acetals from vicinal diols form readily... 

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... 

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

Hydrophilic (Section 19 5) Literally water loving a term applied to substances that are soluble in water usually be cause of their ability to form hydrogen bonds with water Hydrophobic (Section 19 5) Literally water hating a term applied to substances that are not soluble in water but are soluble in nonpolar hydrocarbon like media Hydroxylation (Section 15 5) Reaction or sequence of reac tions in which an alkene is converted to a vicinal diol Hyperconjugation (Section 4 10) Delocalization of a electrons... 

The reaction is based, on the one hand, on the oxidative cleavage of vicinal diols by lead(IV) acetate and, on the other hand, on the reaction of dichlorofluorescein with lead(IV) acetate to yield a nonfluorescent oxidation product. The dichlorofluorescein only maintains its fluorescence in the chromatogram zones where the lead(IV) acetate has been consumed by the glycol cleavage reaction [1],... 

Vicinal effects can also play a part in the course of the reaction utilizing Oppenauer conditions. 1,3-Diols or j5-amino alcohols may not react, presumably on account of format on of an aluminum complex. If oxida-... 

Although lead tetraacetate can attack many polar and nonpolar functions in the steroid molecule, its greatest reactivity is towards vicinal diols. These diols are generally cleaved so rapidly under stoichiometric conditions that other alcohol functions in the molecule need not be protected. Thus lead tetraacetate in acetic acid at room temperature splits the 17a,20-diol group in (9) to yield the 17-ketone (10), the allylic A -3jS-alcohol remaining intact during this oxidation. Since lead tetraacetate is solublein many anhydrous... 

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