The S−H Bond Dissociation Enthalpies and Acidities of Para and Meta Substituted Thiophenols:  A Quantum Chemical Study

Abstract

The accurate S−H bond dissociation enthalpies [BDE(S−H)] for a series of meta and para substituted thiophenols (X−C6H4−SH, X = H, F, Cl, CH3, OCH3, NH2, CF3, CN, and NO2) have been estimated by using the (RO)B3LYP procedure with 6-311++G(2df,2p) basis set. The proton affinities [PA(S-)] at the sulfur site of the corresponding thiophenoxide ions (X−C6H4−S-) and adiabatic electron affinities (EAa) of thiophenoxy radicals have also been evaluated at the same level of calculations. The BDE(S−H) of the parent thiophenol has been evaluated to be 332.6 ± 4.0 kJ/mol, which is in agreement rather with the earlier experimental value of 331.0 kJ/mol (Bordwell et al., J. Am. Chem. Soc. 1994, 116, 6605) than the more recent value of 349.4 kJ/mol (Santos et al., J. Phys. Chem. A 2002, 106, 9883). The effects of para and meta substituents on the BDE(S−H) and PA(S-) have been critically analyzed considering the change in stabilities of the neutral molecule, radical and anions with the change in substituent, and its position. The correlations of Hammett's substituent constants with the BDE(S−H) and PA(S-) values have also been explored.

A theoretical study on NH bond dissociation enthalpies of oxo, thio and seleno carbamates and their N-protonated and N-deprotonated species

“…BDE is calculated as the enthalpy change of the following reaction (1) in the gas phase at 298 K and 1 atm pressure [29][30][31][32][33][34][35][36][37][38]. Calculations were also performed using restricted open (RO) shell formalism at DFT method.…”

The thermodynamics of the isomerization of cyanophenol and cyanothiophenol compounds

“…From a theoretical point of view, it is possible to find few works devoted to the gas-phase O-H and S-H bond dissociation enthalpies of cyanophenols, cyanothiophenols, and Struct Chem (2007) 18: [15][16][17][18][19][20][21][22][23] [16,17]. Very recently, Matos et al [11] used the MP2, BP, and B3LYP methods together with double-ζ basis set to estimate the standard molar enthalpies of formation in the gas-phase of the three cyanophenol isomers 10 , and used the B3LYP method with different basis sets to estimate the enthalpy of formation of anthranil and 1,2-benzisoxazole.…”

Theoretical Investigation on Antioxidant Activity of Phenolic Compounds Extracted from Artocarpus Altilis

“…Nam and coworkers studied the thiophenol, phenylphosphine, toluene, phenolic and their derivatives [15][16][17][18] using DFT with the (RO)B3LYP method and two-layer ONIOM method [19] to accurately determine the BDE and IE values. In the present work, we propose to use the DFT restricted open-shell (RO)B3LYP/6-311++G(2df,2p) for a high layer and the semi-empirical PM6 method for the lower layer with the aim to further shed light on the structural and electronic properties of phenolic extracted from Artocarpus altilis and their radicals.…”