Pinacol: 2,3-Butanediol, 2,3-dimethyl

Photolysis products from ergosterol pro-, pre-, lumi-, and tachy-, 76, 283 Phthalic anhydride 1,3-lsobenzofurandione (85-44-9), 76,123 Pinacol 2,3-Butanediol, 2,3-dimethyl- (76-09-5) 75, 98 Pinacol rearrangement, 76, 296... 

DimethyI-2 3-butanediol has the common name piiuicol. On heating with aqueous acid, pinacol rearranges to pinacolone, 3,3-dimethyl-2-butanone. Suggest a mechanism for this reaction. 

Because reductions by metals often occur as one-electron processes, radicals are involved as intermediates. When the reaction conditions are adjusted so that coupling competes favorably with other processes, the formation of a carbon-carbon bond can occur. The reductive coupling of acetone to form 2,3-dimethyl-2,3-butanediol (pinacol) is an example of such a process. 

Pinacol rearrangement is a dehydration of a 1,2-diol to form a ketone. 2,3-drmethyl-2,3-butanediol has the common name pinacol (a symmetrical diol). When it is treated with strong acid, e.g. H2SO4, it gives 3,3-dimethyl-2-butanone (methyl r-butyl ketone), also commonly known as pinacolone. The product results from the loss of water and molecular rearrangement. In the rearrangement of pinacol equivalent carbocations are formed no matter which hydroxyl group is protonated and leaves. 

The Pinacol Coupling of acetone gives 2,3-dimethyl-2,3-butanediol which is also known as pinacol and the source of the name of this reaction ... 

The pinacol rearrangement is a useful reaction that proceeds via a carbocation rearrangement. Treatment of 2,3-dimethyl-2,3-butanediol, also known as pinacol, with acid results in the formation of a ketone, pinacolone ... 

The alditol crystal structures are conformationally homogeneous. The cocrystallization of different conformers of the same molecule is not common, but sufficient examples are known, especially in hydrogen-bonded crystal structures, for it to be a phenomenon with which crystallographers are familiar. It occurs when there is a population of conformers in solution, all of which have similar energies. A classical example is that of 2,3-dimethyl-2,3-butanediol (pinacol)... 

Jeffrey GA, Robbins A (1978) 2,3-Dimethyl-2,3-butanediol (pinacol). Acta Cryst B34 3817-3820... 

Dimethyl-2,3-butanediol (pinacol) (2.12) on treatment with H2SO4 generates 3,3-dimethyl-2-butanone, commonly known as pinacolone (2.13). Pinacol itself is produced by magnesium reduction of acetone, probably by way of a ketyl intermediate. 

As catalytic tests four reactions, isomerization of 1-butene and methyloxirane, dehydration of 2-propanol and the pinacol rearrangement of 2,3-dimethyl-2,3-butanediol were used. 

Upon treatment with mineral acids, 2,3-dimethyl-2,3-butanediol (often called pinacol) is converted into methyl terf-butyl ketone (often called pinacolone). The... 

The catalysts were pre-activated before use at 450 °C. The olefin 2,3-dimethyl-2-butene (purchased from ACROS, 95%) was distilled before use. H2O2 (30 wt% aqueous) was purchased from Merck, l,3,5-tri-/e/-/-butylbenzeen from Fluka (>97%), pinacol (2,3-dimethyl-2,3-butanediol) from Aldrich (98%), pinacolone (3,3-dimethyl-2-butanone) from ACROS... 

The pinacol rearrangement was first described by Fittig in 1860 [10]-treatment of pinacol (2,3-dimethyl-2,3-butanediol, 1), a ditertiary 1,2-diol, with sulfuric acid resulted in the formation of pinacolone (3,3-dimethyl-2-butanone, 2) (Scheme 1). The overall reaction is dehydration with concomitant migration of a methyl substituent. 

Simple diols have been subjected to the pinacol rearrangement in the presence of Amberlyst 15, a polystyrene sulfonic resin with a high concentration of acidic centers. When excess catalyst is used (g catalyst/g diol = 1.25) pinacol gives 3,3-dimethyl-2-butanone in near quantitative yield (batch reactor, 373 K, 2 h) [33]. Of the two isomeric ketones 3,3-diphenyl-2-butanone (10), formed with phenyl migration, is the sole product when 2,3-diphenyl-2,3-butanediol (9) is reacted (Scheme 6). This feature is very similar to that observed under homogeneous conditions in the presence of sulfuric acid [2]. An arylsulfonic silica catalyst prepared by grafting and sulfonation proved to be less selective [33]. 

A rather limited possibility is the dehydration of certain 1,2- or 1,3-diols to form conjugated dienes. Pinacol (2,3-dimethyl-2,3-butanediol) can be transformed to... 

R-exchanged zeolites are acid materials, and therefore they have been used for carrying out hydration and dehydration of hydrocarbons. This is the case for the hydration of bycyclo[2.2.1]hepta-2,5-diene (Azbel et al. 1989), the cyclodehydration of /V-ethanolamine (Pillai 1995) and the dehydration of 2,3-dimethyl-2,3-butanediol, pinacol (Bezouhanova and Jabur 1994). 

Perhaps the quintessential cationic rearrangement reaction used for synthesis is the Pinacol rearrangement. Fittig was the first to discover that treatment of 2,3-dimethyl-2,3-butanediol (118) with sulfuric acid... 

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