Direct Dynamics Simulations On The Charge Transfer And Proton Transfer Mechanisms Of The ⁴O⁺+¹CH₃I Reaction

The oxygen radical cation?O⁺·?is an important part of the atmospheric chemical network and dominates the ionic composition in the F-region of the ionosphere,and its reaction has become the subject of fundamental research on gas phase ion chemistry.It is extremely reactive and initiates a diverse range of different chemical reactions.The ion is involved in many high energy processes except in atmospheric chemistry,such as plasma corrosion and combustion.Although it plays an important role in various systems,many ion-molecule reactions of O⁺?In order to remember,all of the O⁺· in this text was reduced to O⁺?have not been studied,such as oxygen radical cation with halomethanes.In this paper,we mainly study the ⁴O⁺+¹CH₃I system,in order to comprehensively explore the kinetic information of the reaction of O⁺ with methyl halides and reveal the mechanism of ⁴O⁺+¹CH₃I reaction at the micro level.In this paper,the B3LYP/ECP/aug-cc-p VDZ method and the basis set were used to establish the ⁴O⁺+¹CH₃I reaction potential energy surface.The reaction channel mainly includes: charge transfer,dissociative charge transfer,iodide abstraction,hydrogen proton transfer,substitution process and complex rearrangement process.From the perspective of the reaction energy barrier,the energy barrier of the charge transfer product CH₃I+ is relatively low,and the reaction mainly stays in this process.The ⁴O⁺+¹CH₃I system takes into account the electron spin and charge,so the same product may have different spin multiplicity.In order to judge the product type,we performed a single-point calculation and distinguished by observing the Mulliken charge distribution.According to the experimental conditions,the B3LYP/ECP/aug-cc-p VDZ method was used to directly simulate the ⁴O⁺+¹CH₃I reaction at the collision energy of 4.5 e V,the results show that the ⁴O⁺+¹CH₃I reaction is a direct mechanism: direct rebound and direct stripping.Under these two reaction mechanisms,the direct stripping mechanism is more likely to react,and the formation of different products is mainly the result of direct stripping.Moreover,it is observed that the ⁴O⁺+¹CH₃I reaction has the same reaction path as the Y^-+ CH₃X?Y,X = F,Cl,Br,I?system,that is,processes such as proton transfer and substitution,indicating the ion-molecule reactions of positive and negative ions have similar mechanisms.At the same time,the direct dynamics simulation verified the fact that the charge transfer product CH₃I+ was the main product and also confirmed the existence of some trace products.It provides important theoretical support for the exploration and understanding of oxygen radical cation reactions.