Remarkably, dynamics simulations unveiled the substantial differences between the two reactions investigated here, which the static calculations are incapable of capturing. The static calculations show that the bonds being formed are very similar in TSs of both reactions: 2.23 Å in C60+2,3-dimethyl-1,3-butadiene and 2.27 Å in ethene+1,3-butadiene, despite their very different sizes (Figure ). Also, static intrinsic reaction coordinate 37 (IRC) calculations do not show any big difference in the barrier width (Figure ). In contrast, the quasi-classical MD shows that the bond formation and dissociation in the Diels-Alder reaction of fullerene are slower than in the reaction of ethene after passing the TS (Table ). After crossing the TSs, the bonds are broken and formed much slower in the C60 reaction than in the ethene reaction: 95% of the C-C bonds are formed within 88.0 fs and 69.0 fs, respectively, and 95% of the bonds are dissociated within 372.0 fs and 160.0 fs, respectively (Figure ). Similarly, the average time of bond formation is 23% slower and the average bond dissociation time is slower by a fraction of 2.2. In this analysis, we adopted the previous thresholds in distances: 1.6 Å and 5.0 Å for bond forming and dissociation, respectively (both bonds are considered). In addition, the C60 and 2,3-dimethyl-1,3-butadiene find themselves 50% (30 fs) longer in the transition zone compared to the smaller system of ethene and 1,3-butadiene (Table defined as the forming C-C bond length range that includes 98% of the initial points obtained by a normal mode sampling, see Computational details). Hence, our dynamics simulations uncovered a pedagogically interesting situation when the kinetically faster reaction (according to simple considerations based on TS theory) takes longer to pass through the transition zone (the barrier of C60+2,3-dimethyl-1,3-butadiene reaction is smaller by 7.8 kcal/mol than of ethene+1,3-butadiene, Figure , and, therefore, the former reaction must be faster according to TS theory). Of course, the transition state theory is only concerned with the overall reaction rate for converting reactants to products rather than with the speed of passing through the barrier. Our comparison of dynamics and static calculations clearly shows that only the dynamical calculations can capture the minute details of the barrier shape. Using only static calculations in an attempt to rationalize this dynamics behavior is not an easy task. For example, the barrier width is the first suspect to check for conceptual rationalization why the bonds form and break faster after passing the TS zone, but, as mentioned before, the IRC calculations show essentially the same barrier width for both reactions and that's why cannot explain these trends. Hence, only analyzing the barrier height and width is insufficient. We need to take into account the topology near TS zone and overall barrier shape.