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Structure of 1‐(Arylselanyl)naphthalenes − Y Dependence in 1‐( p ‐YC 6 H 4 Se)C 10 H 7
Author(s) -
Nakanishi Warô,
Hayashi Satoko,
Uehara Tetsutaro
Publication year - 2001
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200110)2001:20<3933::aid-ejoc3933>3.0.co;2-l
Subject(s) - chemistry , crystallography , conformational isomerism , type (biology) , benzene , molecule , naphthalene , homo/lumo , stereochemistry , organic chemistry , ecology , biology
The structures of 1‐(arylselanyl)naphthalenes [1‐( p ‐YC 6 H 4 Se)C 10 H 7 ( 1 ), where Y = H ( a ), OMe ( b ), Me ( c ), Cl ( d ), Br ( e ), COOEt ( f ), and NO 2 ( g )] were determined. The structures of 1 were well classified using types A , B , and C , where the Se−C Ar bond in 1 is placed almost perpendicular to the naphthyl plane in type A and is located on the plane in type B . The type C structure is intermediate between type A and type B . The structures of 1d − 1f are demonstrated to be type A whereas that of 1b is type B by X‐ray crystallographic analysis. The type B conformer is suggested to be favorable in solutions for 1a and 1c based on the NMR‐spectroscopic data. The structure of 1g is assumed to be type A . These results show that the stable structure of 1 must be type A or type B , contrary to early observations of type C for 1,8‐bis(alkyl‐ or arylchalcogeno)naphthalenes. Consequently, the structure of 1 changes dramatically depending on Y in the solid state. We propose that these structures can be explained by the electron affinities, together with the energies of LUMO and LUMO+1 of benzene, substituted benzenes, and naphthalene, which are the components of 1 . In order to clarify the reason for the dramatic change in the structure of 1 with change in Y, ab initio MO calculations were performed on 1 and related compounds. The type A and type B conformations were optimized as stable molecules. Although 1a (type A ) is predicted to be more stable than 1a (type B ) by 1.3 kJ mol −1 , the latter becomes more stable than the former by 8.4 kJ mol −1 if the solvent effects of chloroform are taken into account in the calculations, which was done by applying the IPCM method. The transition state between type A and type B in 1a is similar to type C , which must prevent the monotonical change in the structure of 1 . Compound 1 would be in equilibrium between type A and type B in solutions. The results of the MO calculations on 1 suggest that type A is exclusive for 1g , and probably exclusive for 1f , and predominant for 1d and 1e , while type B is predominant for 1b . The type A and type B would be comparable for 1a and 1c .