19F NMR analysis of the fluorides of perfluorocyclohexane-sulphonic acid and of 3-trifluoromethylperfluorocyclopentane-1-sulphonic acid

From the electrochemical fluorination of the chloride and the fluoride of benzenesulphonic acid, in addition to the main product C₆F₁₁SO₂F, the side products C₅F₈(CF₃)SO₂F, a structural isomer of the main product and C₆F₁₀Cl? SO₂F are also obtained. The NMR analysis of these products was performed. Chemical shift and coupling constant values were obtained for all the compounds. The NMR parameters of the main product are compared with those of perfluoromethylcyclohexane according to the data of Jolley, Sutcliffe and Walker. From the NMR parameters of C₅F₈(CF₃)SO₂F it was possible to demonstrate that substitution on the ring for —SO₂F and CF₃— is of the 1,3 and not the 1,2 type.     

Free boundary enclosure in a three-dimensional filtration problem

We give a lower and an upper estimate for the level of a fluid filtrating through a porous, homogeneous and three-dimensional dam with variable cross-section.     

Chiral acetylenes as synthetic intermediates—II: Optically active 1,4-dialkylbuta-1,3-dienes: synthesis and conformational studies

The synthesis and the physical properties of some optically active 1,4-dialkylbuta-1,3-dienes are reported. The synthetic processes employed were essentially stereospecific. NMR, UV and CD spectra of these compounds provide information on the main conformation of the conjugated diene system, which was shown to be s-trans planar.     

Diisopropylethylamine: An effective catalyst for the introduction of the t-butyldimethylsilyl group

The rapid reaction of t-butyldimethylchlorosilane with alcohols catalysed by diisopropylethylamine at room temperature gave high isolated yields of the t-butyldimethylsilyl ethers.     

Sulle funzioni di più variabili a variazione limitata

Memoria presentata da G. Fichera     

Solution structures and dynamic behaviour of some iron chalcogen derivatives

Summary ¹³C-n.m.r. spectra of (-SR)₂Fe₂(CO)₆, (-SR)₂Fe₂(CO)₅P(n-Bu)₃ and (-X)₂Fe₂(CO)₆ (X=S or Se) show that the solid state structure is maintained in solution. N.m.r. evidence indicates that two isomeric species, not separable by means of the usual physicochemical methods, are present for (-SPh)₂Fe₂(CO)₆ with an overwhelming predominance of theanti form. The phosphine substitutes a COtrans to the iron-iron bond. For any of the iron chalcogen derivatives examined, variable temperature¹³C-n.m.r. spectra show that carbonyl exchange occur in one step. The energy barrier for the exchange of carbon monoxide in the phosphine derivative is lower than that in the unsubstituted complex.