ABSTRACT
The SO sulfuryl bond in a number of representative sulfoxides and sulfones has been studied at the B3LYP/6-311+G(d,p) level in the atoms-in-molecules (AIM) approach involving the AIM delocalization index and the Cioslowski-Mixon localized orbitals and associated covalent bond order. The sulfur-oxygen covalent bond is strongly polarized toward oxygen and the oxygen lone pairs provide significant backbonding to create short and strong SO bonds, similar in nature to those found in the analogous phosphoryl (PO) bond. Although the sulfoxides in general have larger delocalization indices than the sulfones, there is no correlation between these quantities and the bond dissociation energies.
ABSTRACT
Animals of hydrothermal vents live in a unique environment that conceivably could lead to modifications of the usual phosphorus functional groups of importance in living systems. To explore this possibility, specimens of a sea anemone (unidentified) from the TAG hydrothermal field, Mid-Atlantic Ridge, the mussel Bathymodiolus N. sp. from the Mid-Atlantic Ridge, and the tubeworm Riftia pachyptila from the East Pacific Rise were analyzed for compounds containing the carbon&z.sbnd;phosphorus bond. The analysis was based on the use of 31P-nuclear magnetic resonance, which gives signals for C-P compounds that are well separated from those of biological phosphoric acid derivatives. The animals were extracted to provide a lipid- and a water-soluble fraction, leaving an insoluble, largely proteinaceous solid residue. The lipid and residue fractions were subjected to hydrolysis to release bound forms of phosphonic acids. All fractions were analyzed by 31P-NMR. Aminophosphonic acids [primarily NH2CH2CH2PO(OH)2 (1) and CH3NHCH2CH2PO(OH)2 (2)] represented the only type of C-P compound detected. These are well-known constituents of coastal invertebrates. For the mussel and sea anemone, these compounds were present in bound form in both the lipid and insoluble residue. The tube worm contained C-P material only in the insoluble residue, but in quite small amounts. The 31P-NMR method is especially valuable in being able to discriminate between compounds 1 and 2. By this technique, two coastal sea anemones (Tealia felina and Bunadosoma cavernata), previously thought to have 1 as the dominant aminophosphonic acid, were in fact found to be much richer in originally undetected 2. This compound was also detected for the first time in a mussel (Genkensia demissa).
