Studies on ferrocene derivatives XIX. The acylation of [m]-ferrocenophanes and 1,1′-diethylferrocene and the direct conversion of the acylferrocenes to ethers and alkenes

The Vilsmeir formylation of 1,1′-diethylferrocene, [3]- and [4]ferrocenophane has been shown to produce mainly, but not exclusively, the β-isomer and the ratio of β/α for the acetylation of [3]-ferrocenophane depends on the reagent used in the reaction. These aldehydes are directly converted to ethers by reduction with sodium borohydride in alcohol and also to alkenes via the Wittig reaction.     

Reflected shock tube studies of high-temperature rate constants for OH + CH4 --> CH3 + H2O and CH3 + NO2 --> CH3O + NO

The reflected shock tube technique with multipass absorption spectrometric detection of OH radicals at 308 nm has been used to study the reactions OH + CH(4) --> CH(3) + H(2)O and CH(3) + NO(2) --> CH(3)O + NO. Over the temperature range 840-2025 K, the rate constants for the first reaction can be represented by the Arrhenius expression k = (9.52 +/- 1.62) x 10(-11) exp[(-4134 +/- 222 K)/T] cm(3) molecule(-1) s(-1). Since this reaction is important in both combustion and atmospheric chemistry, there have been many prior investigations with a variety of techniques. The present results extend the temperature range by 500 K and have been combined with the most accurate earlier studies to derive an evaluation over the extended temperature range 195-2025 K. A three-parameter expression describes the rate behavior over this temperature range, k = (1.66 x 10(-18))T(2.182) exp[(-1231 K)/T] cm(3) molecule(-1) s(-1). Previous theoretical studies are discussed, and the present evaluation is compared to earlier theoretical estimates. Since CH(3) radicals are a product of the reaction and could cause secondary perturbations in rate constant determinations, the second reaction was studied by OH radical production from the fast reactions CH(3)O --> CH(2)O + H and H + NO(2) --> OH + NO. The measured rate constant is 2.26 x 10(-11) cm(3) molecule(-1) s(-1) and is not dependent on temperature from 233 to 1700 K within experimental error.     

Molecular recognition by macropolycyclic hosts

The formation of complexes between crown ethers and aklylammonium cations may, to some extent, be modelled using standard molecular mechanics methods and an appropriate charge distribution scheme. Monocyclic crown ethers may be developed to give chromoionophores suitable for use in optical fibre based ion sensors. The incorporation of two crown ether systems into polycyclic host molecules which show highly selective complexation of guest bis-alkylammonium cations is described. The scope of these ditopic receptors may be extended by using metalloporphyrins in place of one or both of the crown ether binding sites.     

Plant Responses to Changing Environmental Stress: Cyclobutyl Pyrimidine Dimer Repair in Soybean Leaves

Abstract— We have determined the capacity of soybean seedlings to repair DNA damage by UV doses that do not produce apparent injury in the plants. They remove cyclobutane pyrimidine dimers by both excision and photoreactiva-tion. The rates and relative contributions of these repair processes were determined as a function of initial level of cyclobutyl pyrimidine dimers. Photoreactivation was detected in seedlings at all initial dimer levels. Although excision was not observed at the lowest dimer frequencies, at higher initial dimer levels it was quite effective in dimer removal. The rates of repair in soybean were substantially higher than in alfalfa seedlings at the same DNA damage levels.     

Relationship between retention, linear velocity and flow for counter-current chromatography

A recent paper by Du et al. [J. Chromatogr. A, 835 (1999) 231] showed a very good correlation between the retention of stationary phase and the square root of mobile phase flow (F(1/2)) for 12 different phase systems in counter-current chromatography. This paper shows there is a relationship between the above retention and the linear velocity of the mobile phase. In this way, Du et al.'s results can be related to the kinematics of the mobile phase flow in the tubing. This will open the door for further engineering analysis of this fluid dynamic phenomenon.     

A facile route to a polymer-supported IBX reagent

A three-step preparation of a polymer-supported IBX reagent from poly(p-methylstyrene) is reported. This reagent has been used successfully for the efficient oxidation of a series of alcohols to the corresponding aldehydes.     

MAGNETIC CIRCULAR DICHROISM OF BACTERIOCHLOROPHYLL a IN SOLUTION AND IN A PROTEIN

Abstract— The magnetic circular dichroism (MCD) (300–850nm) of the bacteriochlorophyll (Bchl) a -protein from the green photosynthetic bacterium Prosthecochloris aestuarii 2 K is qualitatively similar to the MCD of Bchl a in methanol and ether solution. This result implies that the transition dipole of the lowest energy electronic transition (near 800 nm) is roughly perpendicular to the transition dipole of the next higher electronic band (near 600nm) for Bchl a molecules in the protein just as it is for molecules in solution. This result provides no support for the recent proposal that interactions with the protein rotates the direction of the transition dipoles of the 800nm band of all the Bchl a molecules in the protein by 90°. While a rotation of the 800nm transition dipoles cannot be rigorously excluded, it would be necessary for the postulated perturbation to rotate the transition dipoles of both the 800 and 600nm bands by 90°. In a broader sense, any postulated perturbation would have to be shown to leave both the absorption spectrum and the MCD largely unaffected. MCD is a more sensitive test than absorption spectroscopy for perturbations of electronic states and changes in the relative orientation of transitions, because it depends on both the magnitudes and directions of at least two electric and one magnetic transition dipole.