A comparative theoretical study of the reactivities of the Al⁺ and Cu⁺ ions toward methylamine and dimethylamine

Abstract

A very recent laser ablation-molecular beam experiment shows that an Al ϩ ion can react with a single methylamine (MA, CH 3 NH 2 ) or dimethylamine (DMA, (CH 3 ) 2 NH) molecule to form a 1:1 ion-molecule complex Al ϩ [CH 3 NH 2 ] or Al ϩ [(CH 3 ) 2 NH)], whereas a dehydrogenated complex ion Cu ϩ [CH 3 N] or Cu ϩ [C 2 H 5 N] is detected, respectively, in the similar reaction for a Cu ϩ ion. Here, we show a comparative density functional theory study for the reactivities of the Al ϩ and Cu ϩ ions toward MA and DMA to reveal the intrinsic mechanism. It is found that the interactions of the Al ϩ ion with MA and DMA are mostly electrostatic, leading to the direct ion-molecule complexes, Al ϩ ONH 2 CH 3 and Al ϩ ONH(CH 3 ) 2 , in contrast to the non-negligible covalent character in the corresponding Cu ϩ -containing complexes, Cu ϩ ONH 2 CH 3 and Cu ϩ ONH(CH 3 ) 2 . The general dehydrogenation mechanism for MA and DMA promoted by the Cu ϩ ion has been shown, and the preponderant structures contributing to the mass spectra of the product ions Cu ϩ [CH 3 N] and Cu ϩ [C 2 H 5 N] are rationalized as Cu ϩ ONHCH 2 and Cu ϩ ON(CH 2 )(CH 3 ). The presumed dehydrogenation reactions are also discussed for the Al ϩ -containing systems. However, the involved barriers are found to be too high to be overcome at low energy conditions. These results have rationalized all the experimental observations well. FIGURE 5. Calculated minimum energy paths for forming the dehydrogenation products ions Al ϩ (C 2 H 5 N) andCu ϩ (C 2 H 5 N). Numbers refer to the relative stability (in kJ/mol) with respect to the separated reactants calculated at the B3LYP/6-311ϩG(d,p) level.

Drag reduction and shear resistance properties of ionomer and hydrogen bond systems based on lauryl methacrylate

“…Therefore, we first conducted molecular dynamics simulation to study the possible microscopic structure and dynamic properties of both systems. The molecular dynamic simulation was carried out in the isobaric-isothermal (NPT) system using the all-atom force field based on OPLS-AA/AMBER force field (Liu et al, 2010). The pressure was 1 bar with a compressibility of 4.5×10 -5 bar -1 .…”