A Combined Density Functional Theory and Coupled Cluster Method Investigation of the Structural Properties and Stabilities of Radical CH₂CP and Its Isomers

Abstract

The doublet potential energy surface of radical system [C(2), H(2), P] is investigated at the UB3LYP/6-311++G(d,p) and UCCSD(T)/6-311++G(2df,2p) (single-point) levels. Eight chainlike and three-membered ring structures are located as energy minima connected by 10 interconversion transition states. At the final UCCSD(T)/6-311++G(2df,2p)//UB3LYP/6-311++G(d,p) level with zero-point vibrational energy correction, species CH(2)CP is found to be thermodynamically the most stable isomer followed by HCCPH, H-cCPC-H, cPCC-H(H), H-cCCP-H, cis-CC(H)PH, trans-CC(H)PH, and CCPH(2) at 11.01, 12.57, 40.07, 43.63, 50.25, 56.82, and 65.36 kcal/mol, respectively. The computed results indicate that the chainlike isomers CH(2)CP and HCCPH and cyclic radical H-cCPC-H possess considerable kinetic stability at extra low pressures and temperatures. Interestingly, radical CCPH(2), whose energy is the highest in all predicted CH(2)CP isomers, can be also regarded as a kinetically stable species with the smallest isomerization barrier of 22.26 kcal/mol at extra low pressures and temperatures. Therefore, considering higher kinetic stability, in addition to the microwave spectroscopy characterized isomer CH(2)CP in previous experiments, the species HCCPH, H-cCPC-H, and CCPH(2) should be considered as excellent candidates for possible experimental observation. Furthermore, the structural nature of stable radical isomers is discussed based on bonding characteristics, single electron spin distribution, and comparison with their analogues.

Theoretical investigation on the radical-neutral reaction mechanism of CP with CH2CO and the structural nature of several low-lying intermediates

“…How- ever, for the adduct I20 (CPCH 2 CO), the CO-loss reaction was not found. Also, we did not locate the possible minimum structure CH 2 PC, which is in good agreement with previous theoretical studies on the CH 2 CP system isomers [37] and HPC molecule [19]. Furthermore, a direct hydrogen abstraction reaction CN + CH 2 CO ?…”

“…Finally, I3 undergoes a CO-loss reaction to P3. For the products P3, cyc-CH 2 PC can easily isomerize into another species CH 2 CP with only a 2.91 kcal/mol reaction barrier height at the UCCSD(T)/6-311++G(2df,2p)//UB3LYP/6-311++G(d,p) level with zero-point vibrational energy correction [37]. Therefore, the final products in Path II should be P1.…”

“…Considering of the product distribution of CN with CH 2 CO, we think that some important and interesting carbon-phosphorusbearing molecules, such as HCP [19][20][21]22], HCCP [23][24][25][26][27], HOCP [28][29][30][31][32][33][34], CH 2 CP [35][36][37], and HCCCP [38][39][40], may be possible products in the reactions of carbon monophosphide (CP), the phosphorus analogue of CN, with CH 2 CO. The CP radical is a well-known interstellar molecule [41,42].…”