Sulfur Hydrogen Bonding in Isolated Monohydrates: Furfuryl Mercaptan versus Furfuryl Alcohol

Abstract

The hydrogen bonds involving sulfur in the furfuryl mercaptan monohydrate are compared with the interactions originating from the hydroxyl group in furfuryl alcohol. The dimers with water were created in a supersonic jet expansion and characterized using microwave spectroscopy and supporting molecular orbital calculations. In furfuryl alcohol-water, a single isomer is observed, in which the water molecule forms an insertion complex with two simultaneous hydrogen bonds to the alcohol (O-H⋅⋅⋅O ) and the ring oxygen (O -H⋅⋅⋅O ). When the alcohol is replaced by a thiol group in furfuryl mercaptan-water, two isomers are observed, with the thiol group preferentially behaving as proton donor to water. The first isomer is topologically equivalent to the alcohol analog but the stronger hydrogen bond is now established by water and the ring oxygen, assisted by a thiol S-H⋅⋅⋅O hydrogen bond. In the second isomer the sulfur group accepts a proton from water, forming a O -H⋅⋅⋅S hydrogen bond. Binding energies for the mercaptan-water dimer are predicted around 12 kJ mol weaker than in the alcohol hydrate (B3LYP-D3(BJ)). The non-covalent interactions in the furfuryl dimers are dominantly electrostatic according to a SAPT(0) energy decomposition, but with increasing dispersion components in the mercaptan dimers, which are larger for the isomer with the weaker O -H⋅⋅⋅S interaction.

Sulfur hydrogen bonding and internal dynamics in the monohydrates of thenyl mercaptan and thenyl alcohol

“…This increment was less notorious in the hydrates of furfuryl alcohol (43.6%) and furfuryl mercaptan (57.3-60.6%), 25 which both retain a O-H•••O H-bond, absent in thenyl mercaptan. This calculation confirms the weaker and more dispersive character of the sulfur interactions in these molecules, 1,2,8,45 also observed in Table 5 for the dimers of water 52 and hydrogen sulphide.…”

“…The experimental work initially examined the conformational landscape and rotational spectrum of the thenyl monomers TM and TA, previously unreported. Similarly to the furfuryl derivatives, 25 the bidimensional potential energy surface is defined by two dihedrals describing the elevation of the side chain with respect to the thenyl ring (  (S1-C2-C6-S7/O7) and the orientation of the terminal thiol/alcohol hydrogen atom (  (C2-C6-S7/O7-H). Molecular orbital calculations in Tables S1-S2 (ESI † ) predicted elevation angles close to +60° (  gauche or G) for the side chain (as in the furfuryl derivatives) and staggered orientations for the terminal alcohol/thiol.…”

The Hydrogen Bond and Beyond: Perspectives for Rotational Investigations of Non‐Covalent Interactions

“…The S···S distance was determined as 2.947(3) from semi-experimental calculations, with ac omplete basis set (CBS)-extrapolated interaction energy of 23.5 kJ mol À1 .N oticeably,t he ( 33 S) nuclearq uadrupole coupling constants and the potentialb arrier for the internal rotation of the methylg roup in DMS are consistentw ith ap artial charge transfer in the dimer from DMS to SO 2 ,a sc onfirmed with the natural bond orbital( NBO) and natural orbital for chemical valence/chargedisplacement( NOCV/CD) methodologies. The origin of the NCI forces was examined with as ymmetry-adapted perturbation theory (SAPT) energy decomposition, [2,74,91] indicating that the electrostatic term is by far the largest contributor (Table 1).…”

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.…”

“…Will the exchange of the two oxygen atoms by sulfur affect the molecular conformation and hydrogen bonding? We address this problem using pulsed-jet chirped-pulsed Fourier transform microwave spectroscopy (CP-FTMW) in the cm-wave region (2)(3)(4)(5)(6)(7)(8). The introduction of CP-FTMW by Pate [29,30] achieves effective multiplexing in the microwave region, allowing routine broadband operation and excellent sensitivity.…”