ISSN:
1572-8854
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Physics
Notes:
Abstract Aromatic derivatives containing two equivalent, sterically hindered, carbonyl groups can exist either as meso or as racemic (d, l) conformers, owing to the noncoplanarity of the Ar and RC=O moieties which creates two centers of chirality. Molecular Mechanics calculations (MM-2) carried out on 2,6-dimethyl-1,5-di(2-methyl)propanoylnaphthalene (1) suggest that the meso form is only 0.5 kcal mol−1 (1 kcal=4.184 J) more stable than the racemic conformer. Solid-state nmr spectra on a bulk sample are not in contrast with the result of the X-ray analysis on a single crystal that the meso conformer is the only species which is present in the solid. On the other hand low-temperature nmr spectra showed that both meso and racemic conformers are present in solution (e.g., 57% and 43% in CD2Cl2 at −85°), the corresponding interconversion barrier (as determined by line shape computer simulation) being 10.7 kcal mol−1.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01160657
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