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Engineering Neutral Organic Bases and Superbases by Computational DFT Methods – Carbonyl Polyenes
Author(s) -
Despotović Ines,
Maksić Zvonimir B.,
Vianello Robert
Publication year - 2006
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/ejoc.200600582
Subject(s) - chemistry , proton affinity , polyene , affinities , cationic polymerization , carbonyl group , radical , hydrogen bond , relaxation (psychology) , conjugate acid , oxygen , proton , computational chemistry , oxygen atom , stereochemistry , molecule , organic chemistry , protonation , ion , social psychology , psychology , physics , quantum mechanics
The gas‐phase proton affinities and basicities of a large number of open‐chain zig‐zag polyenes involving a carbonyl functional group were examined by using the B3LYP/6‐311+G(d,p)//B3LYP/6‐31+G(d) computational scheme. Absolute proton affinities (APAs) increased with the number of polyene subunits. The most basic site in all cases was the carbonyl oxygen. It was conclusively shown that basicity of polyenes was dramatically amplified by substitution of NMe 2 and Me groups at the strategic positions on the molecular backbone. Triadic analysis revealed that the dominating effect was relaxation energy released upon formation of the molecular radical cations. Relation between the relaxation and cationic resonance effect was briefly discussed. Moreover, it was shown that the carbonyl oxygen was more basic than the amino nitrogen of the NMe 2 groups because of the larger bond association energy of the hydrogen atom attached to O compared to N atoms, in the conjugate acid in question. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)