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Why coupling happens at the para and ortho positions?
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Why coupling happens at the para and ortho positions?
Answer: This is an issue of Quantum Chemistry but roughly, the p οrbitals of condensed aromatic rings (like 2-naphthol) do nοt equally contribute to the aromatic conjugation (contrary to the benzene ring), which can explain why diazo coupling of 2-naphthol is favored at the 1-position.
Answer: This is an issue of Quantum Chemistry but roughly, the p οrbitals of condensed aromatic rings (like 2-naphthol) do nοt equally contribute to the aromatic conjugation (contrary to the benzene ring), which can explain why diazo coupling of 2-naphthol is favored at the 1-position.
1). Diazo coupling of N,N-dimethylaniline: Correct! Diazo coupling of N,N-dimethylaniline occurs at the para-position due to the steric hindrance of the N,N-dimethylamine group. 2). Diazo coupling of 2-napthol: Wrong! Ortho- coupling occurs under kinetic control, in contrast to the para- and more extended couplings that occur under thermodynamic control. On the other hand, diazo coupling is effectuated at low temperatures < 5 oC. Thus, diazo coupling of the (non-sterically hindered) 2-napthol, is favored at the ortho- position. Question: Why diazo coupling of 2-napthol is favored at the 1- and not at the 3-position, given that both are ortho- ones?
1). Diazo coupling of N,N-dimethylaniline: Correct! Diazo coupling of N,N-dimethylaniline occurs at the para-position due to the steric hindrance of the N,N-dimethylamine group. 2). Diazo coupling of 2-napthol: Wrong! Ortho- coupling occurs under kinetic control, in contrast to the para- and more extended couplings that occur under thermodynamic control. On the other hand, diazo coupling is effectuated at low temperatures < 5 oC. Thus, diazo coupling of the (non-sterically hindered) 2-napthol, is favored at the ortho- position. Question: Why diazo coupling of 2-napthol is favored at the 1- and not at the 3-position, given that both are ortho- ones?
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Correct! Diazo coupling of N,N-dimethylaniline occurs at the para-position due to the steric hindrance of the N,N-dimethylamine group.
2). Diazo coupling of 2-napthol:
Wrong! Ortho- coupling occurs under kinetic control, in contrast to the para- and more extended couplings that occur under thermodynamic control. On the other hand, diazo coupling is effectuated at low temperatures < 5 oC. Thus, diazo coupling of the (non-sterically hindered) 2-napthol, is favored at the ortho- position.
Question: Why diazo coupling of 2-napthol is favored at the 1- and not at the 3-position, given that both are ortho- ones?
Correct! Diazo coupling of N,N-dimethylaniline occurs at the para-position due to the steric hindrance of the N,N-dimethylamine group.
2). Diazo coupling of 2-napthol:
Wrong! Ortho- coupling occurs under kinetic control, in contrast to the para- and more extended couplings that occur under thermodynamic control. On the other hand, diazo coupling is effectuated at low temperatures < 5 oC. Thus, diazo coupling of the (non-sterically hindered) 2-napthol, is favored at the ortho- position.
Question: Why diazo coupling of 2-napthol is favored at the 1- and not at the 3-position, given that both are ortho- ones?
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