2-butanone, 3,3-Dimethyl

Other Rea.ctlons, The anhydride of neopentanoic acid, neopentanoyl anhydride [1538-75-6] can be made by the reaction of neopentanoic acid with acetic anhydride (25). The reaction of neopentanoic acid with acetone using various catalysts, such as titanium dioxide (26) or 2irconium oxide (27), gives 3,3-dimethyl-2-butanone [75-97-8] commonly referred to as pinacolone. Other routes to pinacolone include the reaction of pivaloyl chloride [3282-30-2] with Grignard reagents (28) and the condensation of neopentanoic acid with acetic acid using a rare-earth oxide catalyst (29). Amides of neopentanoic acid can be prepared direcdy from the acid, from the acid chloride, or from esters, using primary or secondary amines. 

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. 

Pinacolone (3,3-dimethyl-2-butanone) adds to aldehydes in an enantioselective manner when advantage of the induction by a C 2-symmetric boron enolate derived by addition of (2/ ,5/ )-l-chloro-2,5-diphenylborolane is taken. In this way, /i-hydroxy ketones, whose absolute configuration is unknown, arc obtained with 32- 84% cc58. 

Acetone, 2-butanone, 3-methyl-2-butanone, 2-pentanone, 3,3-dimethyl-2-butanone, cyclopentanone, 3-heptanone. 4-methyl-cyclohexanone, 2-octanone, and acetophenone 2 m Porapak Q column, 100-200° at 107min. 

At this temperature 4-(dimethylamino)-3,3-dimethyl-2-butanone, which is formed initially, isomerizes to l-(dimethyl-amino)-4-methyl-3-pentanone. 

The reactions depicted in Fig. 32 are most often carried out at low temperatures. The incursion of a thermal process at elevated temperatures has occasionally been observed. In some cases the thermal oxygenation products are identical to the photochemical products and in other cases are different. For example, when 2,3-dimethyl-2-butene/02 NaY is warmed above — 20 °C a reaction was observed which led to pinacolone (3,3-dimethyl-2-butanone) as the major product.98,110 Pin-acolone is not formed in the photochemical reaction at the same temperature. On the other hand, identical products were observed in the thermal and photochemical intrazeolite oxygenations of cyclohexane.114,133 135 These intrazeolite thermal processes occur at temperatures well below that necessary to induce a classical autooxidation process in solution. Consequently, the strong electrostatic stabilization of oxygen CT complexes may also play a role in the thermal oxygenations. Indeed, the increase in reactivity of the thermal oxygenation of cyclohexane with increasing intrazeolite electrostatic field led to the conclusion that initiation of both the thermal and photochemically activated processes occur by the same CT mechanism.134 Identical kinetic isotope effects (kH/kD — 5.5+0.2) for the thermal and photochemical processes appears to support this conclusion.133... 

Example In the El mass spectrum of 3,3-dimethyl-2-butanone no fragment ion due to McLafferty rearrangement can be observed, because there is no y-hydrogen available (Fig. 6.23). Instead, the products are exclusively formed by simple cleavages as evident from their odd-numbered m/z values. The highly stable tert-butyl ion, m/z 57, predominates over the acylium ion at m/z 43 (Chap. 6.6.2). 

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