Keto-type

In addition to ketone enolates, azaenolatcs with chiral auxiliary groups attached to the nitrogen atom are suitable for the introduction of an a-unsubstituted enolate of the keto-type into an aldehyde in a stereoselective manner (see Section D.1.3.5.). 

Mltsulshi et al. described (20) that 4-OH was in the hydrazo form in polar solvents, and azo form in nonpolar solvents. It was suggested that one hydrogen atom of the hydroxide group at the 4-positlon of the naphthalene ring transferred to the 3-positlon of the azo group, and the tautomerism was established between hydrazo form of the keto type and the azo form of the enol type. In this study, we consider that the spectrum with a peak at the 480 nm... 

Another method of preparing keto aldonic acids, those of the 2-keto type, is by oxidation of the corresponding osone. Neuberg and Kitasato obtained 18 g. of calcium 2-keto-D-gluconate from 20 g. of the osone by the action of bromine at 20 . Similarly, 2-keto-n-galactonic and 2-keto-maltobionic acids were prepared by Kitasato. The substances were characterized generally as the brucine salts because of the amorphous nature of the calcium salts. 

Figure 7.2 (A) Schematic representation of photoinduced proton-transfer reaction in the enol form (E ) and twisting motion in the keto-type (K ) structure to generate the keto-rotamer (KR ) ofexcited l -hydroxy,2 -acenaphthone (HAN). (B) Illustration of HAN molecule in water and complexed with one or two CD nanocavities.

Excitation of the enol species to the Sj state induces a redistribution of electronic charge. For a strong electronic coupling between the initially excited vibronic states and the keto excited state, this charge redistribution occurs on a time scale much faster than 20 fs and establishes an excited state potential energy surface with a minimum for the keto-type configuration of the molecule. 

In contrast to the on-chain phosphorescent palladium centers, which are accidentally incorporated into the polymer backbone by a transmetallation-type side reaction during the synthesis, the formation of keto-type defects in PF derivates is found to be an oxidative degradation process taking place already during synthesis as a consequence of the chemical structure of the monomer units. 

The keto aldonic acids of the hexose series are of the 2- and 5-keto types. The 2-keto acids have been called osonic acids because of their preparation by the oxidation of osones. The 5-keto acids have been termed keturonic... 

The differences between the enol type acetylacetonate complexes, i.e. oxygen bound to metal atom, and the keto type, i.e. carbon bound, are as follows (1) the y-carbon hydrogen stretching frequency is lower by about 150-100cm in the keto form (2) bands due to the asymmetric and symmetric C=0 stretching vibrations appear at I700-I650cm ... 

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