Application of Dimethylformamide in the Determination of Aluminium and Beryllium

Abstract

During sweep polarography in dimethylformamide (DMF) both Al (III) and Be (II) perchlorates produce well defined peaks which can be used for analytical purposes. The extent of solvolysis with time of the perchlorates in this medium was measured. In the presence of a complexing agent such as fluoride ions the rate of solvolysis is much lower and can be neglected. Therefore it is suitable to perform amperometric titration of Al(III) and Be (II) ions with fluoride.     

Synthesis,Crystal Structure and Properties of Ethyl 3,9-Dimethyl-7-phenyl- 6H-dibenzo[b,d]pyran-6-one-8-carboxylate

Ethyl 3,9-dimethyl-7-phenyl-6H-dibenzo[b,d]pyran-6-one-8-carboxylate(C24H20O4, Mr = 372.40) has been synthesized and its structure was determined by 1H and 13C NMR, ESI-MS, elemental analysis, and X-ray single-crystal diffraction. The crystal belongs to the monoclinic system, space group P21/n, with a = 8.3674(11), b = 10.6683(14), c = 11.3817(15) , α = 95.596(2), β = 109.866(2), γ = 94.495(2)°, V = 944.2(2)3, Z = 2, Dc = 1.310 g/cm3, μ = 0.089 mm-1, F(000) = 392, R = 0.0482 and wR = 0.1281 for 2916 observed reflections with I 2σ(I). In the crystal structure, the fused tricyclic nucleus of the title compound is not fully coplanar. Analysis of the crystal packing indicates aromatic π-π stacking interactions occurring between the fused tricyclic aromatic rings of neighboring molecules in which a maximum overlap of the π-electron systems was achieved. Fluorescence and thermal studies indicate that compound 3 has good optical properties and thermal stability.     

Hapten synthesis and antibody production for the development of a melamine immunoassay

The incorporation of melamine into food products is banned but its misuse has been widely reported in both animal feeds and food. The development of a rapid screening immunoassay for monitoring of the substance is an urgent requirement. Two haptens of melamine were synthesized by introducing spacer arms of different lengths and structures on the triazine ring of the analyte molecular structure. 6-Aminocaproic acid and 3-mercaptopropionic acid were reacted with 2-chloro-4,6-diamino-1,3,5-triazine (CAAT) to produce hapten 1 [3-(4,6-diamino-1,6-dihydro-1,3,5-triazin-2-ylamino) hexanoic acid] and hapten 2 [3-(4,6-diamino-1,6-dihydro-1,3,5-triazin-2-ylthio) propanoic acid], respectively. The molecular structures of the two haptens were identified by ¹H nuclear magnetic resonance spectrometry, mass spectrometry and infrared spectrometry. An immunogen was prepared by coupling hapten 1 to bovine serum albumin (BSA). Two plate coating antigens were prepared by coupling both haptens to egg ovalbumin (OVA). A competitive indirect enzyme-linked immunosorbent assay (ciELISA) was developed to evaluate homogeneous and heterogeneous assay formats. The results showed that polyclonal antibodies with high titers were obtained, and the heterogeneous immunoassay format demonstrated a better performance with an IC₅₀ of 70.6 ng mL⁻¹, a LOD of 2.6 ng mL⁻¹ and a LOQ of 7.6 ng mL⁻¹. Except for cyromazine, no obvious cross-reactivity to common compounds was found. The data showed that the hapten synthesis was successful and the resultant antisera could be used in an immunoassay for the rapid and sensitive detection of this banned chemical.     

2′-Lipid-modified oligonucleotides via a ‘Staudinger-Vilarrasa’ reaction

We report a new access to 2′-amido-2′-deoxyuridine via a Staudinger-Vilarrasa coupling reaction for the preparation of lipid-modified oligonucleotides. One or two lipidic moieties were inserted within the oligonucleotidic sequence (LONs) leading to a repertoire of original antagomir-like molecules targeting micro RNA (miRNA or miR). Melting temperature (Tm) experiments revealed that the stability of the duplexes depends on the lipid position and the number of lipid moieties inserted within the oligonucleotide sequence. Single lipid conjugations of positions 11 and 19 of LONs targeting miR-122 do not destabilize the duplexes.     

Synthesis of 9-Substituted Derivatives of 6-(Nitroimidazolyl)thiopurines

The synthesis has been achieved of a series of 9-substituted derivatives of 6-(4-nitroimidazol-5-yl)- and 6-(5-nitroimidazol-4-yl)thiopurines by the reaction of 6-(nitroimidazolyl)thiopurines with alkyl and aralkyl halides, haloalcohols, haloacids and their esters, halo ketones, halo aldehyde acetals, and arylsulfonate esters using potassium carbonate in DMF.     

Kinetics and mechanism of the reaction of substituted benzyl bromides with copper in dimethylformamide

The reaction of copper metal with various substituted benzyl bromides in dimethylformamide has been studied and the kinetic and thermodynamic parameters of the reaction have been obtained. Hammett plots of log(k/k°) vs the substituent constant σ gave good correlations (ρ = 0.24, S_ρ = 0.03, r = 0.951). The structure of the organic group has little effect on the rate of reaction of substituted benzyl bromides with copper. In the absence of atmospheric oxygen, oxidative dissolution of copper occurred by the mechanism of single‐electron transfer with the formation of 1,2‐diphenylethanes and copper(I) complexes. The stereochemistry and intermediate compound were also studied and the reaction mechanism is discussed. Copyright © 2005 John Wiley & Sons, Ltd.