- A facile electrochemical approach for the synthesis of macrocyclic alkanones
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The synthesis of macrocyclic alkanones, viz. cyclotetradecanone 4a, cyclohexadecanone 4b, cyclooctadecanone 4c, cyclopentadecanone 4d and cycloheptadecanone 4e have been carried out by using Kolbe symmetrical/unsymmetrical dimerization followed by cyclization in Na-xylene and subsequent reduction with Zn-HCI in 70-80% yield. The products of anodic cross coupling have been separated by column chromatography over silica gel (60-120 mesh) by eluting with benzene-methanol (95: 5). An effort has been made to optimize the electrochemical step by investigating the effect of different parameters, viz. degree of partial neutralization, current density and electrode material. The products have been characterised by elemental analyses and IR and 1H NMR spectral data.
- Singh, Arpita,Singhal, Nishi,Agrawal, Hemlata,Yadav, Ashok K.
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p. 423 - 426
(2007/10/03)
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- Chain-Substituted Lipids in Monolayer Films. A Study of Molecular Packing
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A series of highly purified fatty acids and phospholipids, each possessing a chain substituent of varying size (methyl, n-butyl, or phenyl) at varying locations (carbon 4, 8, 12, or 16 of an 18-carbon chain) were synthesized.Pressure-area isotherms, obtained with the aid of a film balance, revealed how these molecules, either individually or admixed, pack in monomolecular films.Two examples will illustrate here the type of information secured by the method. (a) The presence of a methyl at carbon 16 of a single phospholipid chain has a negligible effect on the molecular packing within a "liquid" film.A methyl on carbon 16 of both chains, on the other hand, is highly expansive.Even a single methyl at position 8 perturbs the film packing appreciably, thus indicating less available space near the center of the chain. (b) Deviation from ideality in mixed fatty acid films can be explained by interdigitation that reduces steric repulsion among the substituents.It is also possible to observe by means of film balance techniques the extrusion of 8-butylstearic acid when it contaminates a film composed largely of stearic acid.Approximate SHADOW calculations could, in many cases, provide film areas in reasonable agreement with experiment.
- Menger, F. M.,Wood, M. G.,Richardson, S.,Zhou, Q.,Elrington, A. R.,Sherrod, M. J.
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p. 6797 - 6803
(2007/10/02)
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