Moving to the phosphonates (2), inclusion of tunneling also reveals a large enhancement of the semiclassical rate by factors of 124 and 115 for 2H,OMe and 2H,OH at 298.15 K, respectively. For 3OMe,OMe, 4Me,OMe and 5Me,Me, the tunneling effect results in a kT of 77, 60 and 43 at 298.15 K, indicating that 98-99% of the reaction rates for the above cases are due to tunneling. In the case of 5CF3,CF3 and 5CF3,C2F5, tunneling accelerates their semiclassical rate by ~ 3 times, although small compared to the above phosphinylidenes, still accounting for 63 to 65% to the overall reaction rate.