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Acetonitrile(CH3CN)has been detected to be abundant in cometary comae,Titans atmosphere and the interstellar medium,and is also considered to be a probable species on the primitive earth.Oligomers and some amino acids have been identified in acid-hydrolysed(or hydrolysed)products of irradiated CH3CN-H2O binary mixtures.Hence,CH3CN-H2O binary mixtures play an important role in the origin of life region.Protonation products of CH3CN- reacting with water,as crucial intermediates,were considered to initiate partly subsequent sequence of reaction events.Unfortunately,unambiguous reaction mechanisms and products have not been determined so far for these protonation reactions.An ab initio molecular dynamics simulation study of a CH3CN-(H2O)40 cluster with an excess electron(EE)injected vertically is carried out to study the EE solvation dynamics and possible protonation reaction mechanisms and products.Bending vibration of ∠CCN angle and hydration effect of immediate water molecules cooperatively make CH3CN- firstly be in the CN transient,and then two state evolution channels either to the quasi-C2-resonance or to the quasi-N-resonance proceed in the subsequent processes which are controlled by solvent thermal fluctuation.The quasi-C2-resonance is responsible for the PT to cyanide-carbon reaction producing the most stable product CH3CHN radical while the quasi-N-resonance causes the PT to nitrogen reaction producing a sub-stable product trans-CH3CNH radical which can be further converted to CH3CHN radical by a water-mediated hydrogen atom transfer path.