The S−S Bridge: A Mixed Experimental‐Computational Estimation of the Equilibrium Structure of Diphenyl Disulfide

Abstract

The disulfide bridge (À SÀ SÀ ) is an important structural motif in organic and protein chemistry, but only a few accurate equilibrium structures are documented. We report the results of supersonic-jet microwave spectroscopy experiments on the rotational spectra of diphenyl disulfide, C 6 H 5 À SÀ SÀ C 6 H 5 (including all 13 C and 34 S monosubstituted isotopologues), and the determination of the equilibrium structure by the mixed estimation (ME) method. A single conformation of C 2 symmetry was observed in the gas phase. This disulfide is a challenging target since its structure is determined by 34 independent parameters. Additionally, ab initio calculations revealed the presence of three low-frequency vibrations (< 50 cm À 1 ) associ-ated to phenyl torsions which would prevent the calculation of an accurate force field. For this reason, instead of the semiexperimental method, we used the mass-dependent (r m ) method to fit the structural parameters concurrently to moments of inertia and predicate parameters, affected with appropriate uncertainties. The predicates were obtained by high-level quantum-chemical computations. A careful analysis of the results of different fits and a comparison with the ab initio optimizations confirms the validity of the used methods, providing detailed structural information on the title compound and the disulfide bridge.

Rotational spectroscopy of organophosphorous chemical agents: cresyl and phenyl saligenin phosphates

“…The observation of PSP and CBDP organophosphorous compounds with rotational spectroscopy is notorious because of their molecular size, and constitutes a proof-of-concept that high-resolution gas-phase methods can be applied structurally and analytically for the unambiguous characterization of organophosphorous agents, extending previous rotational work on pnicogen and calchogen 37,38 organocompounds. In addition, the introduction of broadband chirp excitation rotational techniques 8,13 contributes to this effort with fast, high throughput and high dynamic range methods, complementing previous frequency-scan techniques 7 and common low-resolution spectroscopic or chromatographic methods.…”

Rotational spectrum and intramolecular hydrogen bonding in 1,2-butanedithiol

“…Additionally, the combination of microwave spectroscopy and internally cooled supersonic jets offers the possibility to generate, stabilize and probe weaklybound aggregates and to analyze the interaction forces [5,6,7]. To date, rotationally resolved investigations of thiols and related sulfides have included mostly small alkyl derivatives like ethanethiol [8], ethanedithiol [9], propanethiol [10], propanedithiol [11], 3-butene-1-thiol [12], 3-butyne-1-thiol [13], cyclopropanemethanethiol [14], mercaptoacetonitrile [15], furfuryl mercaptane [7], diethyldisulfide [16], diallyldisulfide [17] and diphenyldisulfide [18]. For selenols, the 2-propene [19], 3-butene [20], 3-butyne [21], cyclopropylmethyl [22] and propargyl [23] derivatives have been studied.…”

Conformational Equilibria and Molecular Structures of Model Sulfur–Sulfur Bridge Systems: Diisopropyl Disulfide

“…13 Diphenyl disulfide adopts a G conformation with C 2 symmetry, and the torsional angle τ CSSC is 87.21(36)°. 13 The rotational spectrum of dimethyl disulfide of the G configuration is characterized by the internal rotation of two methyl tops. 8 For diethyl disulfide, replacing the two methyl groups of dimethyl disulfide with two ethyl groups leads to more complex conformational behavior: six conformers have been found by ab initio calculations in which GGG and GGG′ conformers have been observed by FTMW spectroscopy.…”

“…Rotational spectroscopic measurements were also carried out for the monosubstituted 13 C and 34 S species for G′GG′ and…”

“…Experimental techniques including vibrational spectroscopy, − electron diffraction, and rotational spectroscopy ,,, have been used to explore the conformations and structures of dialkyl disulfides. The Fourier transform microwave (FTMW) spectroscopic technique can yield accurate information on molecular structures and conformations.…”