Theoretical Calculation of Thermodynamic and Kinetic Quantities for 1,3 Dipolar Cycloaddition Reactions Between Nitrile Sulfides R–CNS (R = H, CH3, Ph and Ph(CH3)3) with 7–10 Membered Simple Cycloalkynes

The 1,3-dipolar cycloaddition reactions also known as the Huisgen cycloaddition are one of the most widely used and versatile preparative methods in hetrocyclic chemistry. In this study, the reactivity and strain energy effect of the simple cycloalkynes with substituted Nitrile sulfides R–CNS (R = H, CH3, Ph and Ph(CH3)3) will be discussed in light of computational studies using DFT methods (B3LYP/6-31G*). The investigation of the structured properties, theoretical thermodynamic and kinetic data of the reactions in 298 K will be presented. The results show increase in the ∆G* by increasing the ring size and decreasing the strain energy of cycloalkynes. Also, the rate constants and the free energy changes in reactions increase as the size of the ring decreases. The relationships of the deviation of the internal bond angle (DIBA, in degrees), π-strain (Sπ) (in kcal mol−1), the bond angle of Csp3–C ≡ C (θº) and ΔG#(kcal mol−1) for the series of cycloalkynes I-1 to I-4 have investigated.