Conformer-specific polar cycloaddition of dibromobutadiene with trapped propene ions

Abstract

Diels–Alder cycloadditions are efficient routes for the synthesis of cyclic organic compounds. There has been a long-standing discussion whether these reactions proceed via stepwise or concerted mechanisms. Here, we adopt an experimental approach to explore the mechanism of the model polar cycloaddition of 2,3-dibromo-1,3-butadiene with propene ions by probing its conformational specificities in the entrance channel under single-collision conditions in the gas phase. Combining a conformationally controlled molecular beam with trapped ions, we find that both conformers of the diene, gauche and s-trans, are reactive with capture-limited reaction rates. Aided by quantum-chemical and quantum-capture calculations, this finding is rationalised by a simultaneous competition of concerted and stepwise reaction pathways, revealing an interesting mechanistic borderline case.

Fragmentation of interstellar methanol by collisions with He˙+: an experimental and computational study

“…For recent examples of the influence of stereochemical effects on the reactivity of other ion-molecule systems at low and ultra low collision energies see for instance. [99][100][101][102][103][104][105] The experimental CSs and product BRs here reported should be used when modelling the abundance of the ubiquitous methanol molecule in the interstellar medium, with special reference to those regions where collisions with He + are expected to be among the main destruction routes.…”

“…For recent examples of the influence of stereochemical effects on the reactivity of other ion–molecule systems at low and ultra low collision energies see for instance. 99–105…”

Progresses in the Study of Low-Energy Ion-molecule Reaction Dynamics※

“…最近, 为此目标, 高蕻研 究组 [39] 利用光电离产生离子方法, 建立了 VMI 装置. 分 子与被约束离子之间进行的可以达到 mK 的冷碰撞过程 是离子-分子反应动力学研究的另一重要研究内容 [40] .…”

Photochemically triggered cheletropic formation of cyclopropenone (c-C3H2O) from carbon monoxide and electronically excited acetylene

“…For more than half a century, pericyclic reactions—reactions that proceed via a single, concerted transition state allowing a cyclic overlap of π and/or σ orbitals—have played a central role in advancing our fundamental understanding of cycloadditions, 1 sigmatropic shifts, 2 group transfer reactions, 2 electrocyclization, 3 and cheletropic reactions. 4,5 The mechanistical understanding of pericyclic reactions has impacted electronic structure and chemical bonding theory 2 as well as preparative organic chemistry on the industrial scale (Scheme 1).…”