Quantum mechanics: cleaning up metaphysical baggage

The dynamic electronic structure of atoms and molecules can be directly observed by means of the (e, 2e) reaction, which measures the distribution of energies and momenta of two electrons in coincidence after a knockout reaction initiated by an electron beam of known momentum incident on a molecular gas target. The molecular state for each event is identified by the electron separation energy. The recoil momentum for each event is known from the difference of measured initial and final momenta. It has been verified that values of this momentum are equal under suitable conditions to the momentum of the electron in the target immediately before knockout. Thus the spherically-averaged electron momentum distribution for each molecular orbital is measured. This is directly related to molecular orbitals calculated by the methods of quantum chemistry. Properties obtained by this method for different types of molecules are discussed.     

2' And 3'-ketonucleosides and their arabino and xylo reduction products: Convenient access via selective protection and oxidation of ribonucleosides

A number of 2',5'- or 3',5'-diprotected ribonucleosides and 5'-protected 2'- or 3'-deoxy-β-D-erythro-pentofuranosyl nucleosides have been oxidized to the corresponding 3' or 2'-ketonucleoside derivatives using chromium trioxide/pyridine/acetic anhydride or dimethyl sulfoxide/ acetic anhydride. Reduction of the carbonyl functions with sodium borohydride gave the inverted arabino, xylo, or deoxy-threo isomers as predominant products by attack at the less hindered α-face of the sugar ring. Parallel reductions using sodium borodeuteride corroborated the epimeric ratios by demonstrating that complete oxidation of the original hydroxyl groups had occurred. The deuterium labeling also aided in making NMR spectral assignments.