. 2021 Aug 19;6(34):21952–21959. doi: 10.1021/acsomega.1c02310

Table 1. Bond Dissociation Enthalpy (BDE) of O-CH₃ for Molecules with Various Substituted Alkyl Groups in Group I and the Corresponding Different Types of Steric Effect Parameters.

substituent	compound#	BDE (kcal/mol)	–E_S^a	V_x^b	ΔD_F^c (10⁴ J/mol)
H	1	65.3	–1.24	0
Me	2	57.9	0	0.52	0
Et	3	58.23	0.07	0.56	0.86
n-Bu	4	58.21	0.39	0.68	0.86
i-Pr	5	56.8	0.47	0.76	2.29
t-Bu	6	50.1	1.54	1.24	3.82

E_S, gross steric effect constants, belongs to kinetic and thermodynamic parameters derived from reaction rate constants of substituents and the reference bases in hydrolytic reactions (data from ref (16)).

V_x, steric parameter, is based on the calculation from volumes and bond lengths defined by van der Waals radii (data from ref (17)).

ΔD_F, steric substituent constant for alkyl groups, is a set of parameters from computational calculation based on molecular mechanics taking into account the tension energy of a molecule including bond length deformation, bond angle tension, bond torsion tension, and nonbond interaction (data from ref (18)).

Table 1. Bond Dissociation Enthalpy (BDE) of O-CH3 for Molecules with Various Substituted Alkyl Groups in Group I and the Corresponding Different Types of Steric Effect Parameters.

Table 1. Bond Dissociation Enthalpy (BDE) of O-CH₃ for Molecules with Various Substituted Alkyl Groups in Group I and the Corresponding Different Types of Steric Effect Parameters.