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Heterogeneous radiolysis of urea. Implications in astrobiology and prebiotic chemistry

100%

Abigail E. Cruz-Hernández, A. E. , Colin-Garcia M. , Heredia-Barbero A. , Negron-Mendoza A. , Ramos-Bernal S.

Open Chemistry

2015

tom 13

nr 1

Urea is an organic molecule present in most living organisms. Historically, it was the first organic molecule synthesized in the laboratory. In prebiotic chemistry, urea readily forms in different laboratory simulations using different energy sources. Furthermore, the role of solid surfaces, particularly minerals, might have been crucial to increase the complexity of the organic matter which may have led to the subsequent emergence of life on Earth. In this work, the radiolysis of urea in presence of a clay is studied to determine to what extent the mineral surfaces influence the decomposition of organics. The results indicate that urea is relatively stable to ionizing radiation in aqueous solutions and up to 20 kGy no decomposition is observed. Moreover, the presence of sodium montmorillonite, by a mechanism until now unknown, affects the radiolytic behavior and urea remains in the heterogeneous solution without a change in concentration even at very high doses (140 kGy). These results indicate that solids could have protected some organics, like urea, from degradation enabling them to remain in the environment on the primitive Earth.

Photocatalytic properties of Ru-doped titania prepared by homogeneous hydrolysis

100%

Houšková V. , Štengl V. , Bakardjieva S. , Murafa N. , Tyrpekl V.

Open Chemistry

2009

tom 7

nr 2

259-266

Nanocrystalline titania particles doped with ruthenium oxide have been prepared by the homogenous hydrolysis of TiOSO4 in aqueous solutions in the presence of urea. The synthesized particles were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM), Selected Area Electron Diffraction (SAED) and Nitrogen adsorption-desorption was used for surface area (BET) and porosity determination (BJH). The photocatalytic activity of the Ru-doped titania samples were determined by photocatalytic decomposition of Orange II dye in an aqueous slurry during irradiation at 365 nm and 400 nm wavelengths. [...]

Synthesis and characterization of thiourea

88%

Dai C. , Zhang H. , Li R. , Zou H.

Polish Journal of Chemical Technology

2019

tom Vol. 21, nr 3

35--39

Herein, a simple and effective method for the preparation of thiourea using a nucleophilic substitution reaction is reported. Urea and Lawesson’s reagent were used as the raw materials to prepare thiourea via a one-step method involving the sulfuration reaction, and the reaction mechanism was analyzed. The effect of the reaction time, reaction temperature, and mass ratio of the raw materials on the yield of thiourea were investigated.The most beneficial conditions used for the reaction were determined to be: Reaction time = 3.5 h, reaction temperature = 75°C, and mass ratio of urea to Lawesson’s reagent = 2:1. Under these optimal conditions, the average yield of thiourea over five replicate experiments was 62.37%. Characterization using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and thermogravimetric analysis (TGA) showed that the as-synthesized substance was thiourea. Our synthetic method has the advantages of high yield, mild reaction conditions and simplicity.