Quantitative Evaluation of the Hydrogen‐Donating Abilities ofAmines and Amides in Acetonitrile

Abstract

In this article, the thermo-kinetic parameter ΔG ¼ 6 °(XH) was used to evaluate the H-donating ability of amine and amide. The second-order rate constants of 41 HAT reactions from amines and amides to CumO * in acetonitrile at 298 K were researched. The thermo-kinetic parameters of 28 amines and 13 amides XH were obtained by the kinetic equation as ΔG ¼ 6 °(CumO * ) = À 41.63 kcal/mol was available in previous work. The scales of the H-donating abilities of these 28 amines and 13 amides were determined by using the thermo-kinetic parameters ΔG ¼ 6 °(XH). The H-donating abilities of amines are stronger than amides, except for two amines without α-CÀ H. The influencing factors of hydrogen donation abilities and the explanation for the HAT reaction sites for amides and amines are discussed from the direction of thermodynamics and kinetics in detail.. The hydrogen donation ability is determined by the combination of thermodynamic bond dissociation free energy ΔG o (XH) and kinetic intrinsic resistance energy ΔG ¼ 6XH/X , that is the thermo-kinetic parameter ΔG ¼ 6 °(XH). The H-donating abilities of these amines and amides were compared with four bioactive antioxidants, NADH coenzyme analogue BNAH, F420H and Vitamin C and E. The results showed that these amines and amides are all weak H-donors.

Structure–activity relationship of alkanes and alkane derivatives for the abilities of C(sp3)H bonds toward their H‐atom transfer reactions

“…According to the physical meaning of Δ G ≠o (XH) discussed in previous articles, 14,24–31 the smaller the value of Δ G ≠o (XH) is, the stronger the H‐donating ability of XH in HAT reaction is. In order to more intuitively study the relationship between molecular structure and Δ G ≠o (XH), the Δ G ≠o (XH) data of different H‐donors are sorted according to their values in Scheme 2.…”

“…XH and Y are hydrogen atom donor (H‐donor) and hydrogen atom acceptor (H‐acceptor), respectively, and their types are also being expanded. The common H‐donors have expanded from the widely studied dihydronicotinamide adenine dinucleotide (NADH) derivatives, 4,5 flavin coenzyme derivatives, 6 and F420H derivatives 7,8 to phenolics, 9–11 amines, and amides 12–14 . Alkanes, such as aliphatic, benzylic, and allylic alkanes, and other derivatives, such as haloalkanes, dimethyl sulfoxide (DMSO), and hexamethylphosphoramide (HMPA), as H‐donors have been the object of extensive investigation and have attracted much attention of organic chemists 15–17 .…”

“…Δ G ≠o (XH) can be used not only to describe the H‐donating ability of XH in a chemical reaction during a certain reaction time but also to predict the rate of HAT reaction (Equation ) by kinetic equation () 25–31 . It has been successfully used to quantitatively evaluate the H‐donating abilities of C(sp 3 )H, NH, OH bonds in NADH derivatives, 25 F420 derivatives, Vitamins C, D, and other bioactive molecules, 26,27 amines and amides, 14 free radicals, 28 activated alkanes, 29 and phenols 30 in HAT reaction. Moreover, it has also been applied to evaluate the H‐donating abilities of C(sp 2 )H bonds in aldehyde molecules 31 .…”

Thermodynamic and Kinetic Studies of the Activities of Aldehydic C−H Bonds toward Their H‐Atom Transfer Reactions

“…It's the kinetic resistance of the HAT reaction as the thermodynamic driving force is zero, which means the kinetic intrinsic resistance barrier of XH in HAT reaction. The thermo‐kinetic parameter Δ G ≠ °(XH) was proposed by a new kinetic model (eq 2) in the previous works, [15,16] which was defined as one half of the sum of the Δ G o (XH) and the Δ G ≠ XH/X (eq 3), usually used not only to describe the actual H‐donating ability of XH in a HAT reaction during a certain reaction time, but also to predict the rate of HAT reaction (eq 1) by kinetic equation 2 [17–22] 23 $$$\vcenter{\openup.5em\halign{$\displaystyle{#}$\cr \Delta G{^{{\ne} }}{_{{\rm XH}/{\rm Y}}}=\Delta G{^{{\ne} }}{^\circ}({\rm XH})+\Delta G{^{{\ne} }}{^\circ}({\rm Y})\hfill\cr}}$$$ $$$\vcenter{\openup.5em\halign{$\displaystyle{#}$\cr \Delta G{^{{\ne} }}{^\circ}({\rm XH})\equiv 1/2[\Delta G{^{{\ne} }}{_{{\rm XH}/{\rm X}}}+\Delta G{^{{\rm o}}}({\rm XH})]\hfill\cr}}$$$ …”

“…The thermo-kinetic parameter ΔG ¼ 6 °(XH) was proposed by a new kinetic model (eq 2) in the previous works, [15,16] which was defined as one half of the sum of the ΔG o (XH) and the ΔG ¼ 6 XH/X (eq 3), usually used not only to describe the actual H-donating ability of XH in a HAT reaction during a certain reaction time, but also to predict the rate of HAT reaction (eq 1) by kinetic equation 2. [17][18][19][20][21][22] DG 6 ¼ XH=Y ¼ DG 6 ¼� ðXHÞ þ DG 6 ¼� ðYÞ (2)…”