The hydrogen bond acceptor (HBA) strength of 31 tetrahedral sulfur bases (thioethers, thiols, disulfides) has been measured by IR spectrometry from: (i) their 1:1 complexation constants with 4-fluorophenol in CCl4 at 25 °C (the pKHB scale); (ii) their HB enthalpies; and (iii) the frequency shifts, Δν(OH), of the ν(OH) band of 4-fluorophenol hydrogen bonded to sulfur. The comparison of the pKHB, ΔH°, and Δν(OH) scales points to their distinctive features. The HBA strength depends on: (i) the nature of the atomic site: oxygen bases are always stronger than sulfur bases, in agreement with the hard and soft acids and bases principle; (ii) the functionality of this atom (for sulfur bases: phosphine sulfur > thioamide > thioketone > thioether > thiol > isothiocyanate ~ disulfide); and (iii) the substituent effects on the function. The main substituent effects are: (i) the polarizability effect of alkyl groups; (ii) the field-inductive effect; (iii) the resonance effect; and (iv) the cyclization effect, which changes the percentage of the s character of sulfur lone pairs. In addition to the attachment to the sulfur atom, IR spectra show the attachment of 4-fluorophenol to the chlorine of MeSCH2Cl and MeSCH2CH2Cl, and the interaction to the π cloud of PhSMe, Ph2S, PhCH2SMe, and EtSCH=CH2. Key words: hydrogen bond, thioethers, thiols, disulfides, pKHB scale.

Proutière's theory of molecular weight (M) determination by Rayleigh scattering has been tested on surfactants in solution, and it has been compared to the classical Carr-Zimm (CZ) method. Both methods make use of time-averaged scattering intensity, refractive index, and density measurements. Monoethers of poly(ethylene glycol) samples have been studied in the range 0.33-4.67 kg/mol of M. Under those conditions, it has been shown that Proutière's method leads to a far better agreement with formula weight (M) values than the CZ method because Proutière theory takes into account the specific mean polarizability of the solvent and derivative of the solution density with respect to the solute mass concentration, which is counter to CZ theory.

No abstract

No abstract

The hydrogen‐bond acceptor properties of MeNCS were investigated in vacuo with theoretical (MP2 and DFT) calculations, in CCl4 and (CF3)2CHOH solutions by Fourier transform infrared spectrometry and in the solid state through the Cambridge Structural Database. These methods show that MeNCS is a sulfur base in hydrogen bonding. The electrostatic potential at the molecular surface is more negative by 36 kJ mol−1 around S than around N. The hydrogen bonding of HF is more favorable to sulfur than to nitrogen by ca 5, 4 and 7 kJ mol−1, respectively, on the dissociation energy, enthalpy and Gibbs energy scales (B3LYP calculations). The selectivity of hydrogen bonding sites appears to be governed by a push–pull mechanism (electrons going from N to S) rather than by hardness. Towards a phenol, the order of sulfur basicity is . Copyright © 2003 John Wiley & Sons, Ltd.