An "Ortho Effect" in Electrophilic Aromatic Nitrations: Theoretical Analysis and Experimental Validation

• Published in: Journal of the Chinese Chemical Society (Taipei) 2014-12, Vol.61 (12), p.1307-1312
• Main Authors: Li, Hui-Jing, Wu, Yan-Chao, Dai, Jian-Hong, Song, b Yan, Cheng, Runjiao, Qiao, Yuanyuan
• Format: Article
• Language: English
• Subjects: Ab initio calculation; Electrophilic aromatic nitration; Ortho effect; Positional selectivity
• ISSN: 0009-4536; 2192-6549
• DOI: 10.1002/jccs.201400092

Usually, a π‐donor substituent acts as an ortho/para directing group in an electrophilic aromatic substitution reaction, and a π‐acceptor substituent acts as a meta directing group. Interestingly, when a π‐acceptor substituent is meta to a π‐donor substituent, certain electrophilic aromatic nitration occurs ortho to the acceptor substituent rather than para. The “ortho effect”, highlighted in various text books, has been tentatively analyzed here based on ab initio calculations. The reliability of the calculations was verified by the corresponding experimental data, including a new‐designed electrophilic aromatic nitration that also gave reasonable product distributions. When a π‐acceptor substituent is meta to a π‐donor substituent, certain electrophilic aromatic nitration occurs ortho to the π‐acceptor substituent rather than para. The “ortho effect”, highlighted in various books such as Smith & March’s book, has been tentatively analyzed here based on ab initio calculations, and the reliability was verified by a new‐designed electrophilic aromatic nitration.