In this work, a conceptual DFT investigation is carried out to study the electrophilic aromatic substitution reaction (SEAr) of 1,2-dimethoxybenzene and 3-(p-nitrobenzoyloxy)-but-3-en-2-one (a captodative olefin). Her...In this work, a conceptual DFT investigation is carried out to study the electrophilic aromatic substitution reaction (SEAr) of 1,2-dimethoxybenzene and 3-(p-nitrobenzoyloxy)-but-3-en-2-one (a captodative olefin). Herein, we have studied the regioselectivity of such reactions considering the effect of solvents of different polarities and the presence of BF3 as the catalyst. Understanding the effect of the solvent and the role of the Lewis catalyst on the pathway of Friedel-Crafts reactions is important to further facilitate the introduction of side chains in aromatic rings with captodative olefins, and thus be able to synthesize compounds analogous to natural products, e.g., α-asarone. Global and local reactivity descriptors were obtained, finding a key role when these reactions take place in the presence of nonpolar solvents. In addition, the Intrinsic Reaction Coordinate diagrams (IRCs) were calculated. Such results of the free activation energy (ΔG‡) clearly show that this reaction is entirely regioselective, forming the unique product in the para position, in agreement with our predictions of the local reactivity descriptors obtained from the Parr functions, wherein the first reaction step, the carbon C4 of the aromatic compound 1,2-dimethoxybenzene is favored. Moreover, from the IRCs, we found that the reactivity of the para adduct increases in the presence of nonpolar solvents. Interestingly, considering a polar solvent (MeCN), the intermediate formed (σ-complex) is more stable since it presents a more significant charge transfer with the solvent than the intermediate in the presence of a nonpolar solvent, making a reaction more challenging to reach when the reaction is carried out in the presence of MeCN because of the increasing of the energetic barrier from σ-complex to the TS2 in the intrinsic reactive coordinate diagram. Therefore, the polarity of the solvent plays an important role, particularly in the activation energy of the TS2. Our computational results explained our experimental results quite well, confirming the importance of the solvent’s polarity to this SEAr reaction and explaining why, experimentally, the nonpolar solvent drove the reaction under catalyzed conditions.展开更多
This letter presents ab initio calculation of Captodative effect on 2,2,2-trifluoroethylamine free radical on STO-3G level. The △Ecd is -50. 15 kJ/mol, which means that this radical is of extra stabilization energy.
Ⅰ. INTRODUCTION A free radical with both electron-donating and electron-withdrawing groups attached to the central carbon atom is said to show special chemical stability. This phenomenon is known as captodative effec...Ⅰ. INTRODUCTION A free radical with both electron-donating and electron-withdrawing groups attached to the central carbon atom is said to show special chemical stability. This phenomenon is known as captodative effect. And the rate, selectivity, yield and mechanism are often influenced in a reaction involving such a radical. Therefore, captodative effect has become an interesting subject to many chemists recently.展开更多
It's urgent to develop benzocyclobutene(BCB)-based polymers with low curing temperature for temperature-sensitive applications such as liquid crystal displays(LCDs)and flexible electronics.Herein,the effect of sub...It's urgent to develop benzocyclobutene(BCB)-based polymers with low curing temperature for temperature-sensitive applications such as liquid crystal displays(LCDs)and flexible electronics.Herein,the effect of substituents on the ring-opening behavior of BCB derivatives was investigated.The ring-opening activation energy barriers(ΔGA)of BCB derivatives with one or two substituents on the four-membered alkyl ring were systematically calculated using the B3LYP function.Both mono-and di-substituted BCBs adopted the conrotatory ring-opening process,obeying the Woodward-Hoffmann's Rules upon heating.The mono-/di-substituted BCBs exhibited 8.2%—69%lowerΔGA compared with BCB,attributed to the electronic effects of the substituents.Disubstituted BCBs with both electron-donating and electron-withdrawing groups,e.g.,1-NH_(2)-8-NO_(2)-BCB,demonstrated the lowestΔGA.In addition,BCB derivatives with amide/ester/acyloxy group modified on C1 position were synthesized as model molecules,and their ring-opening temperature can be decreased by 20℃ compared to the unsubstituted one,also consistent with our calculation results.This work combined theoretical calculation methods with experimental results to provide valuable insights into the design and synthesis of BCB derivatives and next-generation BCB functional packaging materials with low ring-opening temperature.展开更多
文摘In this work, a conceptual DFT investigation is carried out to study the electrophilic aromatic substitution reaction (SEAr) of 1,2-dimethoxybenzene and 3-(p-nitrobenzoyloxy)-but-3-en-2-one (a captodative olefin). Herein, we have studied the regioselectivity of such reactions considering the effect of solvents of different polarities and the presence of BF3 as the catalyst. Understanding the effect of the solvent and the role of the Lewis catalyst on the pathway of Friedel-Crafts reactions is important to further facilitate the introduction of side chains in aromatic rings with captodative olefins, and thus be able to synthesize compounds analogous to natural products, e.g., α-asarone. Global and local reactivity descriptors were obtained, finding a key role when these reactions take place in the presence of nonpolar solvents. In addition, the Intrinsic Reaction Coordinate diagrams (IRCs) were calculated. Such results of the free activation energy (ΔG‡) clearly show that this reaction is entirely regioselective, forming the unique product in the para position, in agreement with our predictions of the local reactivity descriptors obtained from the Parr functions, wherein the first reaction step, the carbon C4 of the aromatic compound 1,2-dimethoxybenzene is favored. Moreover, from the IRCs, we found that the reactivity of the para adduct increases in the presence of nonpolar solvents. Interestingly, considering a polar solvent (MeCN), the intermediate formed (σ-complex) is more stable since it presents a more significant charge transfer with the solvent than the intermediate in the presence of a nonpolar solvent, making a reaction more challenging to reach when the reaction is carried out in the presence of MeCN because of the increasing of the energetic barrier from σ-complex to the TS2 in the intrinsic reactive coordinate diagram. Therefore, the polarity of the solvent plays an important role, particularly in the activation energy of the TS2. Our computational results explained our experimental results quite well, confirming the importance of the solvent’s polarity to this SEAr reaction and explaining why, experimentally, the nonpolar solvent drove the reaction under catalyzed conditions.
文摘This letter presents ab initio calculation of Captodative effect on 2,2,2-trifluoroethylamine free radical on STO-3G level. The △Ecd is -50. 15 kJ/mol, which means that this radical is of extra stabilization energy.
文摘Ⅰ. INTRODUCTION A free radical with both electron-donating and electron-withdrawing groups attached to the central carbon atom is said to show special chemical stability. This phenomenon is known as captodative effect. And the rate, selectivity, yield and mechanism are often influenced in a reaction involving such a radical. Therefore, captodative effect has become an interesting subject to many chemists recently.
基金supported by the National Natural Science Foundation of China(Nos.22075298,2022000168)Beijing Municipal Natural Science Foundation(No,2212053).
文摘It's urgent to develop benzocyclobutene(BCB)-based polymers with low curing temperature for temperature-sensitive applications such as liquid crystal displays(LCDs)and flexible electronics.Herein,the effect of substituents on the ring-opening behavior of BCB derivatives was investigated.The ring-opening activation energy barriers(ΔGA)of BCB derivatives with one or two substituents on the four-membered alkyl ring were systematically calculated using the B3LYP function.Both mono-and di-substituted BCBs adopted the conrotatory ring-opening process,obeying the Woodward-Hoffmann's Rules upon heating.The mono-/di-substituted BCBs exhibited 8.2%—69%lowerΔGA compared with BCB,attributed to the electronic effects of the substituents.Disubstituted BCBs with both electron-donating and electron-withdrawing groups,e.g.,1-NH_(2)-8-NO_(2)-BCB,demonstrated the lowestΔGA.In addition,BCB derivatives with amide/ester/acyloxy group modified on C1 position were synthesized as model molecules,and their ring-opening temperature can be decreased by 20℃ compared to the unsubstituted one,also consistent with our calculation results.This work combined theoretical calculation methods with experimental results to provide valuable insights into the design and synthesis of BCB derivatives and next-generation BCB functional packaging materials with low ring-opening temperature.
