On the existence of ‘thiourea urea magnesium chloride’ and
‘urea thiourea sodium chloride’
Bikshandarkoil R. Srinivasan
Department of Chemistry, Goa University, Goa 403206, India
Email: Telephone: 0091-(0)832-6519316; Fax: 0091-(0)832-2451184
SUPPLEMENTARY MATERIAL FOR ONLINE PUBLICATION
Experimental details of reinvestigation of crystal growth reported by Gopinath et al
All the chemicals used in this study were purchased from commercial sources and were used as received without any further purification. Double distilled water was used as solvent. Infrared (IR) spectra of the samples diluted in KBr were recorded in the region 4000 – 400 cm-1 using a Shimadzu (IR Prestige-21) FT-IR Spectrometer, at a resolution of 4 cm-1. UV-Vis spectra were recorded using an Agilent-8453 UV-Visible spectroscopy system. X-ray powder pattern were recorded on a Rigaku Miniflex II powder diffractometer using Cu-Kα radiation with a Ni-filter.
Reinvestigation of growth of a so called thiourea urea magnesium chloride (1)
A mixture of thiourea (1.520 g, 20 mmol), urea (1.200 g, 20 mmol) and MgCl2·6H2O (4.066 g, 20 mmol) were taken in double distilled water (~ 40 mL) and stirred well to obtain a clear solution. The clear reaction mixture was left undisturbed for crystallization. Slow evaporation of the solvent at ambient temperature (30 ºC) resulted in the separation of transparent crystals after a week. The crystals thus obtained were isolated by filtration, washed with ice cold water and dried in air yielded ~0.95 g and labeled as compound (1) and investigated by qualitative chemical tests and spectral methods like IR, UV-Vis and powder pattern. An additional crystal growth experiment was performed by employing the same amounts of urea (1.200 g, 20 mmol) and MgCl2·6H2O (4.066 g, 20 mol) but an enhanced amount of thiourea (3.04 g, 40 mmol). The yield of the product from this experiment was more than twice (2.31 g) than obtained earlier. The IR and UV-Vis spectra of this product as well as 1was found to be identical to that of pure thiourea (Fig. S1).
Fig. S1 IR spectra of urea (top), thiourea (middle) and a so called thiourea urea magnesium chloride (bottom) showing that TUMC is nothing but thiourea.
Reinvestigation of growth of a so called urea thiourea sodium chloride (2)
A mixture of thiourea (1.520 g, 20 mmol), urea (1.200 g, 20 mmol) and sodium chloride (1.168 g, 20 mmol) were taken in double distilled water (~ 30 mL) and stirred well to obtain a clear solution. The clear reaction mixture was left undisturbed for crystallization. Slow evaporation of the solvent at ambient temperature (30 ºC) resulted in the separation of transparent crystals after ~6 days. The product thus obtained was isolated by filtration, washed with little ice cold water and dried in air yielded ~1.01 g and labeled as compound (2) and investigated by chemical and spectral methods. Compound 2 was confirmed as pure thiourea based on its spectra and powder pattern (Fig. S2)
Fig. S2 The identical X-ray powder pattern confirms that a so called urea thiourea sodium chloride (bottom) is nothing but pure thiourea (top).
Note: All the reactions were performed in millimolar scale (maximum of 20 mmol) and a ratio of 1:1:1 of thiourea:urea:metal salt was employed. No special efforts were taken to grow big blocks of crystals, since the aim of the work was to understand the exact nature of the product formed. It is observed that the yield of the crystalline product in all experiments was always less than the amount of thiourea employed for crystal growth. The use of an enhanced quantity of thiourea resulted in an increase in product yield but still the yield was less than the amount of thiourea employed for crystal growth. A crystal growth reaction was performed by using only thiourrea and metal chloride in 1:1 ratio without using any urea. It is interesting to note that in all cases (use of excess thiourea or use of no urea) the final product obtained is same namely thiourea since all products exhibited the same IR spectrum. The experiments have been performed repeatedly and the results are highly reproducible. The chemical tests confirmed the absence of any chloride or the s-block metal.
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