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Substituent Effect on N ‐Benzylideneanilines by DFT Energy Partition
Author(s) -
Ma YanPing,
Bao Peng,
Yu ZhongHeng
Publication year - 2007
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.200790059
Subject(s) - chemistry , substituent , delocalized electron , resonance (particle physics) , ring (chemistry) , polar effect , molecule , crystallography , density functional theory , computational chemistry , stereochemistry , photochemistry , organic chemistry , atomic physics , physics
To investigate the substituent effect on π‐electron delocalization of the N ‐benzylideneaniline (NBA), the vertical resonance energies Δ E V ( θ ) of eleven substituted NBAs were separated into π and σ parts at the B3LYP/6‐311G(d) level of the Density Functional Theory (DFT). When substituted with an electron‐releasing group –OH, the calculated Δ E V ( θ ) of NBA was increased, indicative of more resonance destabilization than the mother molecule. However, when substituted with an electron‐withdrawing group –NO 2 , the calculated Δ E V ( θ ) values indicated less resonance destabilization. The most destabilizing effect was observed especially when the –OH group located at the ortho ‐position of the aromatic ring in the fragment –NCH–Ar. For most of the substituted NBA molecules, it was the destabilized σ framework that determined the destabilizing feature of the vertical resonance energy, instead of the stabilized π system. When the –NO 2 substituent at the para ‐position of the aromatic ring of the –NCH–Ar group, the π system had the highest stabilizing effect while the ( framework exhibited the highest destabilizing effect. While the –NO 2 substituent was at the para ‐position of the left aromatic ring (Ar–), the NBA had the least vertical resonance energy value.