Monitoring conformational diversity in self-organised monolayers with scanning tunnelling microscopy at near atomic resolution

The evaporation of solutions of dendron-functionalised 2,2'-bipyridines on a graphite surface gives highly ordered monolayers; near atomic resolution STM imaging has allowed a detailed conformational analysis to be made.     

Dirac-Hestenes Lagrangian

We formulate the variational principle of theDirac equation within the noncommutative even space-timesubalgebra, the Clifford -algebra . A fundamental ingredient in ourmultivectorial algebraic formulation is a -complex geometry, . We derive the Lagrangian for theDirac-Hestenes equation and show that it must be mapped on , where denotes an -algebra of functions.     

Mass spectra of flavonoids. Electron impact mass spectra of flavan-4-ols

The electron impact mass spectra of seven flavan-4-ols are reported. Fragmentation pathways were investigated using deuterium labeling and high resolution measurements. The results are consistent with previously proposed ion structures for these compounds, but indicate that the mechanisms suggested for certain hydrogen rearrangements should be revised.     

The occurrence of head-to-head butene units in ethylene-butene copolymers and corresponding ethyl branches in low-density (branched) polyethylenes

A high resolution carbon-13 NMR study of an ethylene-butene copolymer has yielded a spectrum whose resonances could be assigned to isolated ethyl branches, 1,3-diethyl branching as well as 1,2-diethyl branches resulting from head-to-head butene polymerization. All these structures are present in the same sample. An examination of all the published spectra of low-density (branched) polyethylenes has revealed many examples of heretofore unassigned resonances which can be associated with this latter type of diethyl branching in these polymers. Spin-lattice relaxation times have been determined, when feasible, for the carbon atoms in each of the three branched structures.     

Stereoelectronic effects on cyclobutyl participation. The 10-tetracyclo[5.2.1.02,6.O3,9]decyl cation

While the solvolysis of tosylate 5c proceeds very rapidly to generate 4 or its rapidly equilibrating classical alternative, the epimeric compound 6c proved to be unreactive; bond orientation effects are implicated.     

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