Determination of heavy metal concentrations in plants exposed to different degrees of pollution using ICP-AES

Plant samples (Plantago lanceolata – narrow leaf plantain and Cichorium endiviae – endive) were collected in the surroundings of heavy metal emission sources and in other less contaminated areas. After digestion in a closed microwave system using HNO₃, the concentrations of Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn were determined using ICP-AES. Detection limits for all the elements of interest are given. Differences in heavy metal uptake rate between both plant species were observed. The uptake is more intensive for endive than for narrow leaf plantain. High concentrations of some heavy metals were determined in the unwashed plant samples as a result of exposure to aerosols. Tukeys statistical test was used to confirm the discrepancy of Cr concentration in plant samples from various areas. Washing the leaves with water was found to remove a large amount of water-soluble aerosols.     

Zur Synthese von Cyclopentan-2-on-carbonsäureäthylester

Zusammenfassung Es wird eine mit Natriumäthylat in homogener Phase verlaufende intramolekulare Cyclisierung von Adipinsäureester zu Cyclopentan-2-on-carbonsäureester beschrieben.Die Reaktion verläuft inDMSO bzw.DMF als Lösungsmittel in ausgezeichneten Ausbeuten.     

The role of geometry on regioselectivity and rate of fluorination of fluorene and diphenylmethane with Selectfluor F-TEDA-BF4

Diphenylmethane and fluorene were used as target molecules in an investigation of the effect of the geometry of aromatic molecules on the regioselectivity and rate of fluorination with 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor F-TEDA-BF4). In acetonitrile at 80 degrees C ring fluorination of diphenylmethane was accompanied by oxidation of the saturated carbon atom, while in trifluoroacetic acid only ring fluorination with an ortho-para regioselectivity of 1.8:1 was observed. Fluorene was converted in acetonitrile as well as in trifluoroacetic acid into 2- and 4-fluoro substituted products in the relative ratio of 2:1 and 1.2:1, respectively. The reactions in acetonitrile obey a simple rate equation: v = d[F-TEDA]/dt = k2 x [F-TEDA] x [Substrate] and the second order rate constants for the reactions in acetonitrile at 65 degrees C were determined; values of 0.6 x 10(-4) M-1 s-1 for diphenylmethane and 35.5 x 10(-4) M-1 s-1 for fluorene were obtained. The reaction rates for the various functionalisations of fluorene relative to those for diphenylmethane were found to be considerably influenced by the type of functionalisation. Relative rate factors (k(rel) = k2(fluorene)/k2(diphenylmethane)) with values between 59 for fluorination and 712 for chlorination were determined, while the corresponding data for the biphenyl/diphenylmethane pair were only slightly dependent on the type of functionalisation. A reaction pathway involving electron transfer, thus forming cation radical intermediates, was proposed as the main process in the case of fluorination of fluorene with F-TEDA-BF4.     

Fluorination with xenon difluoride. Reaction with halogenated hydrocarbons

Filler and coworkers [1-5] have demonstrated the utility of xenon difluoride as a selective fluorinating agent for aromatic hydrocarbons in the liquid phase, while Mackenzie and coworker [6] have fluorinated aromatic compounds in the vapour phase. We have developed a fluorination reaction of phenyl substituted olefins resulting in high yields of vicinal difluorides [7,8] and trifluoroacetates, depending on the catalyst. In our continued interest in the use of xenon difluoride as a mild fluorinating agent for fluorination of organic compounds, we have tries to fluorinate some heterocyclic ring systems, e.g. imidazo-(1,2-b)-pyridazine, under conditions similar of those used for fluorination of phenyl substituted olefins [7,8,9] (room temperature, methylene chloride as solvent, hydrogen fluoride as catalyst). It is well known that heteroaromatic compounds are less reactive toward electrophilic substitution reactions then aromatic hydrocarbon systems. However, it has been shown that bromination of imidazo-(1,2-b) -pyridazine results in 3-bromo products [10], while in chlorination with phosphorus pentachloride [11], the entering order of chlorine atoms is at position 3 > 2, 7 > 8 > 6 (Radical reactions).     

1,3-Dioxolan-4-ones and 1,3-oxathiolan-5-ones. Configuration of cis and trans isomers

The attempted acid-catalyzed azeotropic removal of water from a mixture containing lactamide and chloral in refluxing toluene lead to the elimination of ammonia; both cis- and trans-5-methyi-2-(trichloromethyl)-1,3-dioxolan-4-one were isolated. A number of 1,3-dioxolan-4-ones and 1,3-oxathiolan-5-ones were obtained by cyclodehydration of aldehydes with α-hydroxy- and α-mercapto-carboxylic acids in the presence of boron trifluoride etherate. Geometric isomers were separated, and their configurations were determined by nuclear magnetic resonance.     

Conversion of a conventional infrared library into computer-readable form

Summary A conventional infrared spectra collection was converted into computer-readable form. The data format is selected to allow for minimal storage requirements, easy handling, and reconstruction of the source curve.

---

Umwandlung einer konventionellen IR-Bibliothek in computerlesbare Form

Zusammenfassung Eine konventionelle Infrarotspektrensammlung wurde in computerlesbare Form übergeführt. Das gewählte Datenformat erlaubt kompakte Speicherung, leichte Verarbeitung sowie Rekonstruktion der Originalkurve.

On leave from the Chemical Institute Boris Kidric, Ljubljana (Yugoslavia).     

Self-diffusion in the isotropic phase of the p-alkoxybenzoic acid homologous series

The temperature dependence of the self-diffusion coefficients of those members of the p-alkoxybenzoic acid homologous series with n = 3 to 8 alkyl chain carbon atoms has been measured in the isotropic liquid phase and a comparison has been made between the activation energies for self-diffusion in the liquid and the solid phase. The self-diffusion coefficients at the isotropic-nematic transition temperatures were found to decrease monotonically with increasing number of alkyl chain carbon atoms.     

Kisik — a combined chemical information system for a minicomputer

A minicomputer-oriented chemical information system (CIS) based on three different Spectrometries, i.e. infrared, mass, and ¹³C-n.m.r., is described and discussed.The system has roughly the same characteristics as CIS's implemented on large mainframe computers: substructure search, library searches on various files, file manipulation, statistical handling of retrieved data, etc. The source package is very suitable and simple for moving the entire CIS from one computer to another. In addition, the system has the Option UPDATE that enables the user to create his own fεles and modify them easily; this is rather difficult and expensive to implement on larger systems because of the very high disk-space price to frequency-of-access ratio. However, the quantity of data is strongly dependent on the disk space. At the moment the system handles 1016 compounds, each of which is described by a chemical name, molecular formula and weight, two-dimensional structure image, infrared, mass, and ¹³C-n.m.r. spectra. All these data for one compound are linked on-line via the identity number of the compound so there is no delay in accessing any of the items mentioned. The entire data bank together with the program package has a 1.8 Mbyte requirement which fits well within the 2.5 Mbyte space available on the small disk used by a PDP $\text{11}\text{34}$ minicomputer.     

NMR self-diffusion study of organic glasses: COANP,MBANP, PNP,NPP

A pulsed field gradient proton spin-echo NMR self-diffusion study of organic glasses COANP, MBANP, PNP and NPP in their liquid and weakly supercooled states was performed. The NMR phase diagrams, based on the proton NMR transverse relaxation time (T ₂) temperature hysteresis data of these materials, clearly give evidence of the onset of a glass phase on cooling the isotropic liquids below their respective melting temperatures. The self-diffusion data exhibit in the supercooled glassy state a non-Arrhenius behaviour and can be described in terms of the Vogel-Fulcher modification of the Arrhenius law,D=D exp{–E _a /[k _B (T–T _VF )]}. The activation energiesE _a and Vogel-Fulcher temperaturesT _VF are 83.2 meV and 239 K for COANP, 66 meV and 249 K for MBANP, and 85 meV and 245 K for PNP, respectively. The flow viscosity data obtained for COANP in the same temperature region as well conform to the Vogel-Fulcher behaviour, exp{E _a ⁽⁾ /[k _B (T–T _VF )]}, withE _a ⁽⁾ =80.4 meV andT _VF =239 K. In case of COANPD was found to increase with decreasing diffusion time in the supercooled (glassy) melt just belowT _M whereas no such behaviour was found aboveT _M .