Enols molecular structure

Figure 4.11 Molecular structures of typical crown-ether complexes with alkali metal cations (a) sodium-water-benzo-I5-crown-5 showing pentagonal-pyramidal coordination of Na by 6 oxygen atoms (b) 18-crown-6-potassium-ethyl acetoacetate enolate showing unsymmelrical coordination of K by 8 oxygen atoms and (c) the RbNCS ion pair coordinated by dibenzo-I8-crown-6 to give seven-fold coordination about Rb.

Jackman and Szeverenyi were the first to systematically correlate the quadrupoiar interaction with molecular structure, i.e. with the aggregation of lithium enolates ". They noted that a tetrameric aggregate had a smaller QSC than a dimeric aggregate, ca 135 kHz compared to an estimate of 230 kHz for the dimer. The QSC of the tetramer was shown to be of the same magnitude in three different ethereal solvents. 

Studies of molecular spectra (UV, IR and NMR) are potentially useful in providing information about aromaticity. Further information may be obtained from magnetic susceptibilities and dipole moment measurements. The UV spectra of pyran-2-one and some of its analogues have been reported (71PMH(3)67), and are consistent with the enol lactone structure (17). 

Jones RDG (1976) The crystal and molecular structure of the enol form of l-phenyl-l,3-butanedione (benzoylacetone) by neutron diffraction. Acta Cryst B 32 2133—2136... 

The enolate and iminate ions of tetra-K-butylammonium salts of carbonyl compounds e.g. malonates) and nitriles e.g. 2-phenylpropionitrile) exhibit special dimeric molecular structures in the solid state and in solution (benzene), held together by multi-... 

Molecular structure of metal enolates TABLE 2. IR data for uranyl fi-ketoenolates [U02(dik)2l... 

Inspection of the molecular structures for n-glucosone (LIII) and kojic acid (LIV) shows that the carbon atom which contained the ketonic carbonyl group in the n-glucosone molecule contains the enolic hydroxyl group in kojic acid. 

The Gp-amido ester enolate complexes (G5Me4SiMe2NBut)TiX[OC(OPr1)=CMe2] (X = C1, Me) have been synthesized, and the molecular structure of the methyl derivative has been determined by X-ray crystallography. 

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