Guanidinium Alkynesulfonates with Single‐Layer Stacking Motif: Interlayer Hydrogen Bonding Between Sulfonate Anions Changes the Orientation of the Organosulfonate R Group from “Alternate Side” to “Same Side”

Hydrolyses of HC?CSO₃SiMe₃ ( 1 ) and CH₃C?CSO₃SiMe₃ ( 2 ) lead to the formation of acetylenic sulfonic acids HC?CSO₃H?2.33 H₂O ( 3 ) and CH₃C?CSO₃H?1.88 H₂O ( 4 ). These acids were reacted with guanidinium carbonate to yield [⁺C(NH₂)₃][HC?CSO₃^?] ( 5 ) and [⁺C(NH₂)₃][CH₃C?CSO₃^?] ( 6 ). Compounds 1 – 6 were characterized by spectroscopic methods, and the X‐ray crystal structures of the guanidinium salts were determined. The X‐ray results of 5 show that the guanidinium cations and organosulfonate anions associate into 1D ribbons through ${{\rm R}{{2\hfill \atop 2\hfill}}}$ (8) dimer interactions, whereas association of these ions in 6 is achieved through ${{\rm R}{{2\hfill \atop 2\hfill}}}$ (8) and ${{\rm R}{{1\hfill \atop 2\hfill}}}$ (6) interactions. The ribbons in 5 associate into 2D sheets through ${{\rm R}{{2\hfill \atop 2\hfill}}}$ (8) dimer interactions and ${{\rm R}{{3\hfill \atop 6\hfill}}}$ (12) rings, whereas those in 6 are connected through ${{\rm R}{{1\hfill \atop 2\hfill}}}$ (6) and ${{\rm R}{{2\hfill \atop 2\hfill}}}$ (8) dimer interactions and ${{\rm R}{{4\hfill \atop 6\hfill}}}$ (14) rings. Compound 6 exhibits a single‐layer stacking motif similar to that found in guanidinium alkane‐ and arenesulfonates, that is, the alkynyl groups alternate orientation from one ribbon to the next. The stacking motif in 5 is also single‐layer, but due to interlayer hydrogen bonding between sulfonate anions, the alkynyl groups of each sheet all point to the same side of the sheet.     

Bloch oscillations and an accelerator for cold atoms

Received: 30 May 1997     

Chargements axisymétriques d'un bicouche transversalement isotropeAxisymmetric loading on a transversely isotropic two-layered medium

An exact three-dimensional analysis is developped for an axisymmetric loading acting on the surface of a semi-infinite medium composed by two transversely isotropic materials. The loading is assumed to be parallel to the elastic symmetry axis of the upper layer. The solutions of a concentrated force and a uniform loading distributed on a circle are obtained by exact integral expressions. The numerical results are performed to show the anisotropic effect with isovalue curves of stress. To cite this article: C. Ruimy, M. Dahan, C. R. Mecanique 330 (2002) 469–473.     

Preparation of ethyl 2-aryl 2,3-alkadienoates via palladium-catalyzed selective cross-coupling reactions

Pd-catalyzed cross-coupling reactions of aryl iodides containing not only an electron-donating group but also an electron-withdrawing group on the aryl ring with organoindium reagents generated in situ from indium and ethyl 4-bromo-2-alkynoates produced selectively ethyl 2-aryl-2,3-alkadienoates in good yield.     

Specific heat of liquid hexane up to 500 MPa and from 243 to 473 k from the heat of compression

Abstract

The expansivity of n-hexane was measured through the heat of compression up to 500 MPa in the 243–473 K temperature range. Details about the experiment are given. From the fit to our data, the pressure variation of the specific heat C_p, in the same pressure-temperature domain, is computed; good agreement is obtained with available high pressure data.     

Viscoelastic properties of laminated bodies

In this paper we define a class of two-phase laminate composites for which the constituent elements are either linearly elastic or exhibit viscoelastic effects. We determine the viscoelastic behaviour of the equivalent homogeneous transversely isotropic medium by a single time-independent memory function.