Norma Sbarbati Nudelman

[(Ph)2(NMe2)C(OLi)⋅THF]2: Crystal Structure of the Tetrahedral Intermediate Formed in the Reaction of N,N‐Dimethylbenzamide and Phenyllithium

Information on the reaction path for the 1,2-eliminiation of LiNMe2 to form benzophenone is provided by the X-ray crystal structure analysis of the tetrahedral adduct [(Ph)2 (NMe2 )C(OLi)⋅THF]2 (a portion of the structure is shown schematically), which is prepared from N,N-dimethylbenzamide and phenyllithium. A N1-Li1 interaction, which is not observed, would lead to loss of the anomeric effect (nN →σ*C-O ) as well as high conformational strain along the C1-N1 bond.

[(Ph)2(NMe2)C(OLi)⋅THF]2: Kristallstruktur der tetraedrischen Zwischenstufe aus der Umsetzung von Benzoesäuredimethylamid mit Phenyllithium

Aufschlusse uber den Reaktionspfad der zu Benzophenon fuhrenden 1,2-Eliminierung von LiNMe2 liefert die Kristallstrukturanalyse des tetraedrischen Adduktes [(Ph)2(NMe2)C(OLi)⋅THF]2 (siehe Ausschnitt aus der Struktur), das aus Benzoesauredimethylamid und Phenyllithium erhalten wurde. Eine N1-Li1-Wechselwirkung, die nicht auftritt, wurde den Verlust des anomeren Effekts (nNσ*C-O) sowie hohe konformative Spannung an der C1-N1-Bindung bedeuten.

Tributyltin bioaccumulation and toxic effects in freshwater gastropods Pomacea canaliculata after a chronic exposure: field and laboratory studies

Freshwater samples and gastropod mollusks (Pomacea canaliculata) were collected at 5 sampling stations located along the lower Río de la Plata basin, Argentina, to assess the extent of tributyltin (TBT) contamination. Determined data revealed the presence of TBT and some of its breakdown products (dibutyltin: DBT, and monobutyltin: MBT) in all freshwater samples and also in soft tissues of P. canaliculata gastropods. Chronic bioassays (6 months) were performed using female gastropods that had been reared under laboratory conditions and exposed to a similar TBT concentration than the value determined in freshwater samples (1 µg L−1). The aims of this study were to evaluate the extent of TBT accumulation, the tissue distribution, and the effects on selected biomarkers (activity of superoxide dismutasa: SOD, activity of catalase: CAT, levels of total glutathione: t-GSH, lipid peroxidation, and activity of acetylcholinesterase: AChE). Gonads presented the highest accumulation, followed by the cephalopedal region, albumin gland, and finally hepatopancreas. Both metabolites, DBT and MBT, were also found. All exposed female animals presented development of a penis reflecting the potential of TBT as an endocrine disrupting chemical for this gastropod species. Results on the selected biomarkers confirmed additional adverse effects induced by TBT. An increase in CAT activity and changes in t-GSH levels are indicative of alterations on the cellular redox status. The inhibition of AChE could reflect signs of neurotoxicity. Altogether, these results reveal a negative impact on the health of this gastropod population.