The crystal structure of heptane-1,7-di­carboxyl­ic acid (azelaic acid), C₉H₁₆O₄, has been redetermined at 180 K. The molecular units have twofold symmetry and are linked via the ubiquitous syn-syn carboxyl­ic acid dimer to form infinite chains running approximately along the [01] vector.

The crystal structure of octane-1,8-di­carboxyl­ic acid (sebacic acid), C₁₀H₁₈O₄, has been redetermined at 180 K. The molecular units are centrosymmetric and linked via the ubiquitous syn-syn carboxyl­ic acid dimer to form infinite chains running along the [01] vector.

The structure of the title compound, tripotassium trans-tetra­cyanidodioxidotechnetate(V), is isotypic with its Re analogue. The [TcO₂(CN)₄]³⁻ trans-tetra­cyanido­dioxido­technetate anion has a slightly distorted octa­hedral configuration. The Tc atom is located on a center of inversion and is bound to two O atoms in axial and to four cyanide ligands in equatorial positions. The Tc—O distance is consistent with a double-bond character. The two potassium cations, one located on a center of inversion and one in a general position, reside in octa­hedral or tetra­hedral environments, respectively. KO and KN inter­actions occur in the 2.7877 (19)–2.8598 (15) Å range.

The reaction between dibenzyl­ideneacetone (dba) and tri­isopropyl sulfoxonium tetra­fluoro­borate has been reinvestigated. The stereochemistry of the major diasteromeric bis­(gem-dimethyl­cyclo­propane) adduct has now been assigned as [(1RS,3RS)-2,2-dimethyl-3-phenyl­cyclo­prop­yl][(1SR,3SR)-2,2-dimethyl-3-phenyl­cyclo­prop­yl]methanone, C₂₃H₂₆O, by X-ray crystallographic studies on a twinned crystal. The asymmetric unit contains two mol­ecules of the adduct, the conformations of which differ in the orientation of the phenyl ring relative to the adjacent cyclo­propanated double bond. The carbonyl groups of each adduct are aligned approximately along the a axis and in opposite directions to each other. The mol­ecules pack to give a sinusoidal pattern along the b axis. This is the first acyclic bis­(dimethyl­cyclo­prop­yl) ketone for which an X-ray crystal structure determination has been reported, and is also the first bis-cyclo­propanated dba analogue. The knowledge that the major diastereomer has the meso structure (and therefore the confirmation that the minor isomer is the racemate) will prove invaluable in future studies to utilize bis­(dimethyl­cyclo­prop­yl) ketones as reagents, in rearrangement processes, and as potential ligands and ligand precursors in organometallic chemistry.