Synthesis of di- and tetraalkyl-3-piperazinoisoquinolines and related compounds as potential antidepressant agents

A series of di- and tetraalkyl-3-piperazinoisoquinolines and related compounds was synthesized via di- and tetraalkylated 1-indanones as intermediates.     

Enantiomeric 3,7-Dimethylocta-1,7-dienes as Useful Chiral Building Blocks. A New Access to Both Optical Antipodes of Natural (E)-3,7-Dimethyloct-2-ene-1,8-diol and (E)-3,7-Dimethyloct-2-ene-1,8-dicarboxylic Acid

Ozonolysis of the easily available monoterpenoids (?)- 1 and (+)- 1 leads in high yield to the ketoaldehydes (?)- 4 and (+)- 4 , which serve as convenient intermediates for efficient new routes to both optical antipodes of the naturally occurring octenediol (E)- 2 (Monarch butterfly secretion product) and octene-dicarboxylic acid (E)- 3 (Callosobruchus chinensis sex pheromone). All steps proceed with almost complete retention of configuration, ensuring the synthesis of the target compounds with high optical purity.     

Electrochemical stripping with carbon fiber electrodes in a microliter-capacity cell

The construction of a microcell with an in-situ mercury-plated carbon fiber electrode for the application of electrochemical stripping techniques is described. The performance of the cell is compared to a conventional mercury-film glassy carbon electrode in large-volume cells with special emphasis on the effects of mass transport and oxygen interference. Effective mass transport is provided withouth forced convection and oxygen does not appear to influence the response of the carbon fiber electrode. The dependence of the a.s.v. and p.s.a. signals on the deposition time with the microcell deviated from linearity at deposition times above 3 min because of depletion effects and decreased concentration of oxidizing agent, respectively. Good reproducibility of lead determinations in the μg 1^?1 range by a.s.v. and p.s.a. was achieved in successive scans at the same fiber and in consecutive tests of identical samples. Calibration plots were linear in the 0.01–10 mg 1^?1 range. Sample volumes down to 5 μl were used in determining cadmium and lead. The detection limits for both elements obtained with a.s.v. and p.s.a. after 5-min preconcentration were 1 and 3 μg1^?1, respectively, or in absolute mass 5 pg and 15 pg, respectively.     

Isospin selection rules for real photons observed in the6Li(γ,d) reaction

The high spin structure of the nucleus¹²⁹Ba has been investigated using a¹⁸O induced reaction. The known bands could be followed up to a maximum spin (55/2) ?. Some 56 states and 78 transitions could be placed in the level scheme. Band crossings were established in both positive and negative parity structures. They display features of strong polarization effects due to the alignment of h_11/2 protons.     

The kinetics of methane ignition in fuel-rich HCCI engines: DME replacement by ozone

Fuel-rich combustion of methane in a homogeneous-charge compression-ignition (HCCI) engine can be used as a polygeneration process producing work, heat, and useful chemicals like syngas. Due to the inertness of methane, additives such as dimethyl ether (DME) are needed to achieve ignition at moderate inlet temperatures and to control combustion phasing. Because significant concentrations of DME are then needed, a considerable part of the fuel energy comes from DME. An alternative ignition promotor known from fuel-lean HCCI is ozone (O₃). Here, a combined experimental and modelling study on the ignition of fuel-rich partial oxidation of methane/air mixtures at Φ = 1.9 with ozone and DME as additives in an HCCI engine is conducted. Experimental results show that ozone is a suitable additive for fuel-rich HCCI, with only 75 ppm ozone reducing the fuel-fraction of DME needed from 11.0% to 5.3%. Since ozone does not survive until the end of the compression stroke, the reaction paths are analyzed in a single-zone model. The simulation shows that different ignition precursors or buffer molecules are formed, depending on the additives. If only DME is added, hydrogen peroxide (H₂O₂) and formaldehyde (CH₂O) are the most important intermediates, leading to OH formation and ignition around top dead center (TDC). With ozone addition, methyl hydroperoxide (CH₃OOH) becomes very important earlier in the compression stroke under these fuel-rich conditions. It is then later converted to CH₂O and H₂O₂. Thus, ozone is a very effective additive not only for fuel-lean, but also for fuel-rich combustion. However, the mechanism differs between both regimes. Because less of the expensive additives are needed, ozone could help improving the economics of a polygeneration process with fuel-rich operated HCCI engines.