A DFT study on the mechanism of the gas phase reaction of ground-state Y (4d15s2,2D) with 2-butyne

Abstract The reaction of ground-state Y with 2-butyne has been investigated in detail using B3LYP method. Four pathways for elimination of H 2 were identified. Two isomers, Y(HCCC)CH 3 and Y(H 2 CCCCH 2 ) were assigned to the observed product, YC 4 H 4 . The calculated PESs suggest that the concerted H 2 -elimination leading to Y(H 2 CCCCH 2 ) + H 2 product is the most favorable pathway. For the elimination of CH 3 , combining the results of this work with our previous study on Y + propyne reaction, a general mechanism for the reactions of Y with 2-alkynes bearing RC C CH 3 structure was established: Y + RC C CH 3  → π-complex → TS(H-migration) → HY(CH 2 CC)R → TS (C C insertion) → (CH 2 ) HY CCR → TS(H-migration) → H 3 C Y CCR → CH 3  + YC 2 R. Such mechanism was found to be always energetically more favorable than the direct sp–sp 3 C C bond insertion mechanism. Further, such mechanism can also be applied to the elimination of CH 4 and it can be described as: Y + CH 3 C CCH 3  → π-complex → TS (H-migration) → HY (H 2 CCC) CH 3  → TS(C C insertion) → (H 2 CCC) HY CH 3  → TS(H-migration) → CH 4  + YC 3 H 2 .