Butane-2,4-dione

Biacetyl (butan-2,3-dione) [431-03-8] M 86.1, b 88 , d 0.981, ni 1.3933. Dried with anhydrous CaS04, CaCl2 or MgS04, then vacuum distd under nitrogen, taking the middle fraction and storing it at Dry-ice temperature in the dark (to prevent polymerization). 

The EPR spectra of semidione radical anions can provide information on the spin density at the individual atoms. "The semidione derived from butane-2,3-dione, for example, has a spin density of 0.22 at each oxygen and 0.23 at each carbonyl carbon. The small amount of remaining spin density is associated with the methyl groups. This extensive delocalization is consistent with the resonance picture of the semidione radical anion. 

Oihydrohjran CfDtonakJehyde Melhacrolein Methytvinylketone 2-But>TO-1,4-diol Butane-2,3-dione Crotonic(E)acid Methacrylic acid Vinylacetate Methyl aaylate... 

Intermolecular photocycloadditions of alkenes can be carried out by photosensitization with mercury or directly with short-wavelength light.179 Relatively little preparative use has been made of this reaction for simple alkenes. Dienes can be photosensitized using benzophenone, butane-2,3-dione, and acetophenone.180 The photodimerization of derivatives of cinnamic acid was among the earliest photochemical reactions to be studied.181 Good yields of dimers are obtained when irradiation is carried out in the crystalline state. In solution, cis-trans isomerization is the dominant reaction. 

This result suggests that the 1,4-dipolar intermediate (133) is involved in this last reaction, and in accord with this is the formation of a 1 1 1 adduct of tetrachlorobenzyne, acetone and butan-2,3-dione, which has been shown to have the structure (134) 168>. 

Further research within in our laboratory has illustrated that certain substrates bearing trans-hydroxyl groups can be directly protected using cyclic and acyclic diones, thus alleviating the requirement for prior formation of the tetramethoxydiacetals.6 For example, butane-2,3-dione has proved particularly useful for the preparation of butane diacetal (BDA) derivatives, which serve as useful alternatives to cyclohexane diacetal (CDA) derivatives. 

Individually indexed compounds are f Acetaldehyde oxime, 0865 Acetone oxime, 1258 Azoformaldoxime, 0815 Benzaldehyde oxime, 2760 Bromoacetone oxime, 1201 Butane-2,3-dione dioxime, 1595... 

Bromocyclohexanone, 2392 Butane-2,3-dione dioxime, 1595 f Butyl isocyanate, 1931 Chloroacetamide, 0788 4-Chloro-2-aminophenol, 2303... 

Butanediol dehydration, 41 155 Butane-2,3-dione synthesis, 41 302-303 Butanethiol, dissociation, 37 292 -Butanol, see 1-Butanol 2-Butanol... 

We start with butane-2,3-dione dioxime, more commonly known as dimethylglyoxime (dmg). It is a classic reagent for the analysis of NP, the green aqueous solution of metal ions transforming into a vibrantly red precipitate of Ni(dmg)2 complex it is one of the stars of the show in Ponikvar and Liebman s analytical chemistry chapter in the current volume. Here the stereochemistry is well-established and well-known—both OH groups are found on the same side as their adjacent CH3 group on the butanedione backbone. There have been several measurements of the enthalpy of formation of this species for which we take the one associated with this inorganic analytical chemistry application, i.e. with diverse metal complexes and chelates . 

FIGURE 6. Novel Br0nsted-type plots log k vs pA"a for the reaction of butane-2,3-dione monoxi-mate (Qx , ) and 4-chlorophenoxide (4-ClC5H40 , O) with 4-nitrophenyl diphenylphosphinate (PNPDPP) at 25.0 °C. Reprinted with permission from Tarkka and Buncel, J. Am. Chem. Soc., 117, 1503. Copyright (1995) American Chemical Society... 

Pyrazoldiamines were reported in CHEC-II to react with hydroxy ketones to yield pyrazolo[3,4-/ ]pyrazines. Similar to this, pyrazolopyrazines 285 are obtained at room temperature from reaction of 284 with glyoxal (and butane-2,3-dione) in good yield (Equation 39) <2004TL4105>. 

More complex is the oxidation of 2,3-butandiol (I) the first oxidation product, acetoin (II), can be obtained at 333 K. with 96% selectivity at 62% conversion if the solvent is water. When methanol is used as the solvent, the reaction rate is decreased, but the product distribution is the same. When acetone is used as the solvent, a larger amount of butane-2,3-dione (III) is obtained, as summarized in Table IV. 

Acetic acid (IV) is formed when acetoin or butane-2,3-dione is oxidized in acetone, even at low temperatures. The use of acetone significantly changes the relative rates of the different oxidation reactions. The possibility that acetone takes part in promoting the oxidation of acetoin deserves further investigation. 

Second-order rate constants for reactions of hydroxide ion and butane-2,3-dione monoximate ion with various phosphate, phosphinate, and thiophosphinate esters pass through minima with decreasing water content of water-MeCN and water-/-BuOH mixtures. The initial inhibition is offset by stabilization of die charge-delocalized TSs.234... 

In the example included here (Expt 5.100) ethyl methyl ketone is nitrosated to butane-2,3-dione monoxime, which is then reacted with hydroxylamine to give the dioxime, dimethylglyoxime, the well-known reagent for nickel. 

---