Theoretical study on the enthalpies of adduct formation between alkyl iodides and chlorine atoms.

• The enthalpies of adduct formations (EAFs) between alkyl iodides (RI) and chlorine (Cl) atoms are investigated. • The EAFs decreases when the number of alkyl substituents on the C atom bonded to I atom is increased. • The mechanism of the trend of the EAFs is suggested. The equilibrium geometries for the ground state of the adducts formed between alkyl iodides (RI) and chlorine (Cl) atoms were optimized, and the enthalpies of adduct formations (EAFs) were obtained. The EAFs decreased when the number of alkyl substituents on the C atom bonded to I atom was increased. This trend suggests that the amount of charge transferred from the electron-donating alkyl group to I Cl increases in accordance with the number of substituents, which results in the stabilization of the adduct. Charge density distribution between the Cl and H atoms was an additional mechanism to stabilize the adducts. [ABSTRACT FROM AUTHOR]