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Separation of the energetic and geometric contribution to the aromaticity. Part IX. Aromaticity of pyrazoles in dependence on the kind of substitution

✍ Scribed by Tadeusz M. Krygowski; Romana Anulewicz; Michal K. Cyrański; Agnieszka Puchala; Danuta Rasala

Publisher
Elsevier Science
Year
1998
Tongue
French
Weight
312 KB
Volume
54
Category
Article
ISSN
0040-4020

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✦ Synopsis

Crystal and molecular structures of the 4-(4'-N, N-dimethylaminophanyl)-3,5-dimethyl-t,7diphenyl-bis-pyrazolo[3,4-b;4',3'-e]pyridine (1) and 3,5-dimethyl-1,4,7-triphenyl-bifepyrazolo[3,4b;4',3'-e]pyridine (If) are reported, with R = 0.0505 and 0.0538, ~ly.

Application of the HOMA model ~ to molecular geometry of the title compounds enriched by the data for pyrazoles retrieved from CSD and from RHF/6-311G** ab-initio calculations led to the conclusion formulated as a rule that decrease of aromaticity of pyrazole is caused by an increase of the double bond character of the exo~clic bonds with substituents attached to C3 and C4 atoms in the ring.

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