Mechanism of adsorption,electroreduction and hydrogenation of compounds with ethylenic bonds on platinum and rhodium: Part II. Comparison of the electroreduction and catalytic hydrogenation processes

The catalytic liquid-phase hydrogenation of maleic acid on platinum and rhodium has been investigated. It is shown that the rate-determining step of this process as well as of the electroreduction process of maleic acid is the interaction of the chemisorbed particle of maleic acid with the adsorbed hydrogen which is formed at the preceding rapid stage of either the dissociative adsorption of molecular hydrogen, or the electrochemical stage of hydrogen ion discharge. The rate of the process with the same degree of surface coverage with hydrogen and chemisorbed particles of maleic acid does not depend on whether the process is carried out catalytically or electrochemically, on whether maleic acid and hydrogen were preliminarily adsorbed on the surface of the electrode-catalyst or not. With due regard for the mutual influence of chemisorbed particles participating in the rate-determining stage, the main kinetic equations for the electroreduction and catalytic hydrogenation processes have been derived. The difference in the rates of electroreduction of maleic acid on platinum and rhodium, with the same degree of electrode surface coverage with reactants, is shown to be the result of differences in the adsorption heats (or bonding strength with the surface) of hydrogen and maleic acid on these two metals. Experimental procedures are described in Part I [1].     

Hydroxyethylation of uracil,adenine, and cytosine with ethylene carbonate

It was established that both 1-(2-hydroxyethyl)uracil and 3-(2-hydroxyethyl)-uracil, which are converted to 1, 3-bis (2-hydroxyethyl) uracil, are formed in the first step of the reaction of uracil with ethylene carbonate. The simultaneous formation of 9- (2-hydroxyethyl) adenine and 3- (2-hydroxyethyl) adenine occurs in the reaction of adenine with ethylene carbonate. The only product of hydroxyethylation of cytosine was 1-(2-hydroxyethyl) cytosine. Methods for the analytical separation of the hydroxyethylation products and the preparative isolation of the 1- and 9-hydroxyethyl derivatives are proposed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 684–689, May, 1978.     

Structures of decorine and delcoridine

In order to confirm the structures of the alkaloids delcorine and delcoridine (O-demethyldelcorine) suggested previously, a direct passage has been performed from delcoridine to delcorine and from delcorine to delphatine. It has been shown that the configuration of C₁ - OCH₃ previously suggested for delcorine and delcoridine is incorrect — it should be .Institute of the Chemistry of Plant Substances of the Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 621–623, September–October, 1981.     

Rates of vibrational and dissociative excitation of diatomic molecules in atom-molecule collisions in a hot gas

Vibrational relaxation and dissociation in O₂-Ar at low O₂ contents are considered. The populations of the vibrational levels are found as functions of time. The vibrational relaxation time and the dissociation rate constant at 3000 to 20 000 K are calculated. The relaxation equation for the vibrational energy per unit volume in the presence of dissociation is considered.     

Membrane osmometry of aqueous micellar systems

Summary The number average micellar molecular weights,M _n , were determined with the application of membrane osmometry, for various nonionic and a cationic surfactant, in aqueous solutions. These results show that these micelles are monodisperse, as also reported by other investigators. The dependence ofM _n on temperature was also studied. It was found that both the nonionic and the cationic micelles showed an abrupt change in logM versus temperature plots. In the case of nonionics, the abrupt change was observed at approximately 30 °C lower than the cloud-point.Presented at the 25th Colloid-Meeting in Munich, October 13–15, 1971.     

Investigations of copper,silver and bismuth deposition on palladium in perchloric acid media

Investigations have shown that copper and silver ions deposited at more positive potentials than the Nernst potential—similarly to bismuth ions—are not adsorbed but form alloys with palladium. Similarly, in the case of metal deposition via the ionization of sorbed hydrogen, the same alloys were formed as observed by the potentiostatic method.     

Variation of calculated single bond lengths in saturated hydrocarbon and silicon hydride molecules

A series of saturated X_nH_m (X being either C or Si) molecules is studied using the MINDO /3 and MNDO quantum-chemistry procedures. We find that the proximity of H atoms tends to shorten X? X bonds, and that this effect is (especially for MINDO /3) much larger than a similar trend in experimental values. The connection between this and hybridization values calculated from localized orbitals is investigated. It is found that the hybridization model works well for X? H bonds, whereas for X? X bonds non-σ-bond effects also play a significant role. It is shown that the changes in electronic structure may be directly connected to differences in X and H atomic levels, so that similar bond length differences may be expected in other molecular orbital calculations.     

The mass spectra of 2-alkyl N-methyl pyrrolidines

The mass spectra of a series of 2-alkyl N-methyl pyrrolidines have been examined and fragments which may be pyrrole type structures are apparent. These ions are most prominent in the spectra of the long chain alkyl derivatives.     

Flow-injection determination of nonylphenol in liquid media using a piezoelectric immunosensor

A piezoelectric flow immunosensor for the rapid determination of nonylphenol in aqueous solutions was developed. An aminophenol-protein conjugate (4-AP-GA-BSA) immobilized on the presilanized surface of a silver electrode was used as a bioreceptor coating of the sensor. The effects of the nature and concentration of monoclonal and polyclonal antibodies on the analytical signal of the sensors were studied; the activity of immunoreagents was evaluated based on the binding constants K _b. The cross reactions of various phenols with antibodies were studied and the cross reaction percentages were found. A procedure for the flow-injection determination of nonylphenol in liquid media was developed using a piezoelectric immunosensor as a detector. The calibration graph was linear over the concentration range 1–20 ng/mL; the detection limit for nonylphenol was 0.8 ng/mL.     

Chemoselective cross-metathesis reaction. Application to the synthesis of the C1-C14 fragment of amphidinol 3

[reaction: see text] An efficient synthesis of the C1-C14 fragment of amphidinol 3 is described. The synthesis is based on chemoselective cross-metathesis reactions and enantioselective allyltitanations.