Sensing free sulfur dioxide in wine

Sulfur dioxide (SO2) is important in the winemaking process as it aids in preventing microbial growth and the oxidation of wine. These processes and others consume the SO2 over time, resulting in wines with little SO2 protection. Furthermore, SO2 and sulfiting agents are known to be allergens to many individuals and for that reason their levels need to be monitored and regulated in final wine products. Many of the current techniques for monitoring SO2 in wine require the SO2 to be separated from the wine prior to analysis. This investigation demonstrates a technique capable of measuring free sulfite concentrations in low volume liquid samples in white wine. This approach adapts a known colorimetric reaction to a suspended core optical fiber sensing platform, and exploits the interaction between guided light located within the fiber voids and a mixture of the wine sample and a colorimetric analyte. We have shown that this technique enables measurements to be made without dilution of the wine samples, thus paving the way towards real time in situ wine monitoring.Tanya M. Monro, Rachel L. Moore, Mai-Chi Nguyen, Heike Ebendorff-Heidepriem, George K. Skouroumounis, Gordon M. Elsey and Dennis K. Taylo

Cubyl and 4-fluorocubyl radicals

The ESR spectra of cubyl and 4-fluorocubyl radicals were observed in solution; they indicated that hyperconjugation was slight, but that significant spin density reaches C(3) and C(4).</p

Cubyl and 4-fluorocubyl radicals

The ESR spectra of cubyl and 4-fluorocubyl radicals were observed in solution; they indicated that hyperconjugation was slight, but that significant spin density reaches C(3) and C(4).</p

Homolytic Reactions of Homocubane and Basketane:Rearrangement of the 9-Basketyl Radical by Multiple β-Scissions

Methods are described for the synthesis of 9-hydroxy-and 9-bromopentacyclo[4.3.0.02, 5.03, 8.04, 7]nonane (homocubane derivatives) and for the same derivatives of pentacyclo[4.3.0.02, 5.03, 8.04, 7]decane (basketane). The 9-homocubyl and 9-basketyl radicals generated from these precursors were observed by EPR spectroscopy. In spite of their very large strain energies, both radicals rearranged extremely slowly, and unrearranged products were obtained from homolytic reactions in solution at temperatures below 150 °C. At higher temperatures the 9-basketyl radical rearranged by a cascade of three β-scissions, the ultimate product being 1 -(4-cyclobut-2-enyl)cyclohexa-2, 4-diene. The Arrhenius parameters for the rearrangement were found to be log(Ar/s-1) = 13.6, Er= 13.5 kcal mob-1. The 9-homocubyl radical did not rearrange even at 220 °C. An explanation as to why these cage radicals rearrange at least 6 orders of magnitude more slowly than the related cubylcarbinyl radical is presented, and semiempirical SCF-MO calculations are reported.</p

Homolytic Reactions of Homocubane and Basketane:Rearrangement of the 9-Basketyl Radical by Multiple β-Scissions

Methods are described for the synthesis of 9-hydroxy-and 9-bromopentacyclo[4.3.0.02, 5.03, 8.04, 7]nonane (homocubane derivatives) and for the same derivatives of pentacyclo[4.3.0.02, 5.03, 8.04, 7]decane (basketane). The 9-homocubyl and 9-basketyl radicals generated from these precursors were observed by EPR spectroscopy. In spite of their very large strain energies, both radicals rearranged extremely slowly, and unrearranged products were obtained from homolytic reactions in solution at temperatures below 150 °C. At higher temperatures the 9-basketyl radical rearranged by a cascade of three β-scissions, the ultimate product being 1 -(4-cyclobut-2-enyl)cyclohexa-2, 4-diene. The Arrhenius parameters for the rearrangement were found to be log(Ar/s-1) = 13.6, Er= 13.5 kcal mob-1. The 9-homocubyl radical did not rearrange even at 220 °C. An explanation as to why these cage radicals rearrange at least 6 orders of magnitude more slowly than the related cubylcarbinyl radical is presented, and semiempirical SCF-MO calculations are reported.</p

The preparation of space-separated chelating agents based on the 3,6-dipyridyl pyridazine ligand

Linear, bent, cavity and Z-shaped molracs of varying length are converted to end-functionalised bis-chelating agents 3 containing the 3,6-(di-2′-pyridyl)pyridazine ligand by reaction of their norbornenyl end-groups with 3,6-di-(2′-pyridyl)-s-tetrazine 4 followed by oxidation with DDQ, sometimes in a one pot reaction. New representative molracs as well as new chelating agents are described. Molecular mechanics (MM2) has been used to evaluate geometric parameters for these systems which display ligand separations from 6-21 Å; however shorter or longer systems are possible