1 .3-DIOXOLANE-4.5-DICARBOXYLIC ACID, 2,2-DIMETHYL-, BIS

DIOXOLANE-4,5-DICARBOXYLIC ACID, 2,2-DIMETHYL-, BIS(l-METHYLETHYL) ESTER, (4R-TRANS)-, 65, 230... 

DIISOPROPYL (2S,3S)-2,3-0-IS0PR0PYLIDENETARTRATE (1,3-Dioxolane-4,5-dicarboxylic acid, 2,2-dimethyl-, bis(l-methylethylJester, (4R-trans)-J... 

As Section IV will be mostly devoted to 2,4-pentanedione, acacH, it is worthwhile to dwell on this well studied species. The rate of interconversion between the keto and the enol form of acacH is rather slow at room temperature , thus they can be simultaneously detected by NMR spectroscopy it has been observed that the lower the polarity of the solvent, the higher the percentage of the enol tautomer . Electron diffraction studies indicate that in the gas phase acacH adopts the enol configuration with a keto/enol ratio of 8/92. More recently, an X-ray analysis of acacH, carried out at 110 showed that it exists as a mixture of the two enol forms 86 and 87, with the enolic hydrogen atom equally distributed over two positions close to the oxygen atoms as in 88. It should be noted that inclusion compounds containing different host molecules show different ratios of acacH in the enol form. For example, acacH exists as a dynamically averaged 1 1 mixture of 86 and 87 in an inclusion complex with l,T-binaphthyl-2,2 -dicarboxylic acid as host , while l,l-bis( >-hydroxyphenyl)cyclohexane and (4R,5R)-trawi-4,5-bis(hydroxydiphenylmethyl)-2,2-dimethyl-l,3-dioxolane include acacH in pure enolic form. ... 

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