Improved syntheses of some monochloro- and monobromo-8-quinolinols

Summary Procedures were developed for the preparation of the 2-, 3-, 4-, and 6-monosubstituted chloro and bromo 8-quinolinols which afforded greater yields and/or reduced the number of steps in the preparation. 100 MHz¹H-NMR spectra for the 12 possible monochloro and monobromo analogues are given.

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Verbesserte Synthese von Monochlor- und Monobrom-8-chinolinolen

Zusammenfassung Es wurden Verfahren entwickelt, um 2-, 3-, 4- und 6-Chlor bzw. -Brom-8-chinolinole in besseren Ausbeuten und/oder bei reduzierter Anzahl von Synthesestufen herzustellen. Die¹H-NMR-Spektren der 12 möglichen Monochlor- und Monobromverbindungen werden angegeben.

     

On the calculation of induced electric and magnetic moments of atoms and molecules

We present a many-electron method for calculating first and second order perturbed wavefunctions due to external electric and magnetic fields, which identifies the important correlation effects for the response function a priori and calculates them variationally. It is accurate, economical and applicable to ground and excited states with the same ease. Thus, it presents a useful alternative to the well-known coupled Hartree-Fock methods. As an application of this method, we calculate the static electric dipole polarizability of the Be ground state. We find α_d = 5.49 ų in agreement with recent extensive calculations.     

Photolysis of (η5-C5H5)2V(CH3)2: II . Photo-induced formation of ethane

Photolysis of (η⁵-C₅H₅)₂V(CH₃)₂ results in the formation of methane and ethane. The percentage of ethane detected in the evolved gas can vary from a trace to 70%. The percentage of ethane formed is dependent on the solvent, the concentration of (η⁵-C₅H₅)₂V(CH₃)₂, time and temperature. The results of oxidation and reduction reactions involving (η⁵-C₅H₅)₂V(CH₃)₂ are also presented.     

Bioluminescent detection of insect pheromones using an enzyme-based flow injection analysis system

The combination of flow injection analysis with chemiluminescent detection is shown to provide extremely selective and sensitive detection of insect pheromones which possess an aldehyde moiety. The flow injection analysis system provides reproducible control of both the reaction chemistry and the sample introduction process. Microliter volume samples can be precisely handled and analyzed with this experimental configuration. The detection system is based on the luciferase-catalyzed oxidation of reduced flavin mononucleotide which occurs in the presence of aldehydes with carbon backbones of between 14 and 16 carbons. A limit of detection of 3 fmol of tetradecyl aldehyde is demonstrated and the system is shown to be insensitive to the presence of various organic solvents up to concentrations of approximately 10%. The key experimental variables which control sensitive detection of pheromone at the femtomole level with be investigated and discussed.     

Prediction of Complexation Properties of Crown Ethers Using Computational Neural Networks

A computational neural network method was used for the prediction of stability constants of simple crown ether complexes. The essence of the method lies in the ability of a computer neural network to recognize the structure-property relationships in these host-guest systems. Testing of the computational method has demonstrated that stability constants of alkali metal cation (Na+, K+, Cs+)-crown ether complexes in methanol at 25 °C can be predicted with an average error of ±0.3 log K units based on the chemical structure of the crown ethers alone. The computer model was then used for the preliminary analysis of trends in the stabilities of the above complexes.     

Preparation,stability, reactivity and synthetic utility of a cadmium stabilized complex of difluoromethylene phosphonic acid ester

Diethyl bromodifluoromethyl phosphonate reacts readily with cadmium metal to form a stable cadmium complex. Depending on solvent, this functionalized organocadmium reagent exhibits stability for days to months. It reacts with a variety of electrophiles and serves as a synthetically useful source for the introduction of the difluoromethylene phosphonate group into organic compounds.The synthetic utility of a wide variety of fluoromethylene phosphonium ylides has been a major effort in our laboratory over the past several years [1]. The generation and capture of difluoromethylene ylides ($\text{1}$) as a general route to difluoromethylene olefins has been of especial interest to us [2]. In an effort to increase the nucleophilicity of the ylide, we have attempted to prepare the analogous phosphonate ylide ($\text{2}$). Although we have achieved modest success [3] by $\text{insitu}$ capture of ($\text{2}$) in the reaction of

sodium dialkyl phosphites with diethyl bromodifluoromethylphosphonate ($\text{3}$), attempts to pregenerate ($\text{2}$), either from diethyl difluoromethylphosphonate ($\text{4}$) or ($\text{3}$), have met with little success. ($\text{2}$) appears to have minimal stability even at low temperatures, and scale up processes of synthetic value would seem to be difficult.     

Influence of PAR and UV-A in determining plant sensitivity and photomorphogenic responses to UV-B radiation

The role of photosynthetically active radiation (400-700 nm) (PAR) in modifying plant sensitivity and photomorphogenic responses to ultraviolet-B (280-320 nm) (UV-B) radiation has been examined by a number of investigators, but few studies have been conducted on ultraviolet-A (320-400 nm) (UV-A), UV-B and PAR interactions. High ratios of PAR-UV-B and UV-A-UV-B have been found to be important in ameliorating UV-B damage in both terrestrial and aquatic plants. Growth chamber and greenhouse studies conducted at low PAR, low UV-A and high UV-B often show exaggerated UV-B damage. Spectral balance of PAR, UV-A and UV-B has also been shown to be important in determining plant sensitivity in field studies. In general, one observes a reduction in total biomass and plant height with decreasing PAR and increasing UV-B. The protective effects of high PAR against elevated UV-B may also be indirect, by increasing leaf thickness and the concentration of flavonoids and other phenolic compounds known to be important in UV screening. The quality of PAR is also important, with blue light, together with UV-A radiation, playing a key role in photorepair of DNA lesions. Further studies are needed to determine the interactions of UV-A, UV-B and PAR.     

Solvent triggering between conformational states in amphiphilic shape-persistent macrocycles

The amphiphilic shape-persistent macrocycle 1 containing four phenol-OH groups as polar side groups and four hexyloxy groups as nonpolar side groups in an adaptable arrangement was recrystallized from solvents of different polarity. X-ray crystallography reveals that the conformation of the macrocycle is solvent dependent such that in the pyridine solvate only two of the nonpolar side groups point outward while in the THF solvate all four of them point outward. Moreover, in the latter case the three-dimensional packing leads to the formation of a supramolecular channel structure with a large pore size.     

A new method for gaining insight into the chemistry of drying mineral surfaces using ATR-FTIR

Although it is understood that the chemical environment at a drying surface is likely to be quite different from that at a fully hydrated surface, the difficulty of quantitative measurement has meant that this potentially crucial aspect of surface chemistry has gone largely overlooked. As a result, most of our understanding comes from measurement before and after drying, with a gray region of speculation in between. An interesting natural example is the paradoxical reduction of Mn oxides in moist soils as they dry, because drying is usually considered an oxidative process. This phenomenon indicates that important chemical changes are occurring during drying and an approach is needed to probe the chemistry of drying surfaces. Here we show the suitability of attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy for real-time, in situ investigation of the drying solid-water interface, using the change in surface pH as an example. This was achieved by adsorbing thymol blue pH indicator (pK(a)=1.65) onto a natural Mn-rich clay and observing the real-time pH change, which dropped from pH 5 to below pH 1.65 with the removal of free water from the surface.     

Increased oxygen transfer in a yeast fermentation using a microbubble dispersion

A microbubble dispersion (MBD) was used to supply oxygen for aerobic fermentations in a standard 2 L stirred tank fermenter. The microbubble dispersion was formed using only surfactants produced naturally. Growth rates ofSaccharomyces cerevisiae cultures were found to be equal or greater with MBD sparging than with gas sparging. The oxygen transfer coefficent with MBD sparging was found to be 190/h and independent of impeller speed from 100–580 rpm. The oxygen transfer coefficient with air sparging rose from 55 to 132/h over the same range of impeller speeds. Power requirements for the fermenter systems were estimated.