unable to understand..

as far as i know pinacole is a reaction.....which is not in syllabus...[1][1]

pinacole is formed wen acetone reacts wid Mg(Hg) + water gives pinacole. i m not very sure if it's in syllabus. bt if u want d mechn then i'l give u. also this is covered in aldehyde,keto ,and acids chap.

pinacole is in syllabus..(if its not then u shld study it as it may come in the form of a comprehension next year)

no...its okk.....!!

Reaction mechanism

The first step in the reaction mechanism is one-electron reduction of the carbonyl group by a reducing agent such as magnesium to a ketyl radical anion species. Two ketyl groups react in a coupling reaction yielding a vicinal diol with both hydroxyl groups deprotonated. Addition of water or another proton donor gives the diol. With magnesium as an electron donor, the initial reaction product is a 5-membered cyclic compound with the two oxygen atoms coordinated to the oxidized Mg2+ ion. This complex is also broken up by addition of water with formation of magnesium hydroxide. The pinacol coupling can be followed up by a pinacol rearrangement. A related reaction is the McMurry reaction, which uses titanium trichloride or titanium tetrachloride in conjunction with a reducing agent for the formation of the metal-diol complex, and which takes place with an additional deoxygenation reaction step in order to provide an alkene product.

THIS IS JST D REACTN MECHANISM OF PINACOLE FORMATION

pinacole means highly substitued alcohol .........

n we hav d rxtion
pinacole ----- converted to pinacolone in syllb

pinacolone is highly subtitued ketone

Pinacol itself is produced by magnesium reduction of acetone, probably by way of a ketyl intermediate. Since the diol is symmetrical, protonation and loss of water takes place with equal probability at either hydroxyl group. The resulting 3º-carbocation is relatively stable, and has been shown to return to pinacol by reaction in the presence of isotopically labeled water. A 1,2-methyl shift generates an even more stable carbocation in which the charge is delocalized by heteroatom resonance. Indeed, this new cation is simply the conjugate acid of the ketone pinacolone, which is the product of repeated rearrangements catalyzed by proton transfer. Each step in this rearrangement is potentially reversible, as demonstrated by the acid catalyzed dehydration of pinacolone (and pinacol) to 2,3-dimethyl-1,3-butadiene under vigorous conditions.

mechanism:

some selected pinacole rearangement