- Melamine-(H2SO4)3/melamine-(HNO3)3 instead of H2SO4/HNO3: A safe system for the fast oxidation of thiols and sulfides under solvent-free conditions
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Melamine reacted with neat sulfuric acid and fuming nitric acid readily to form two new organic solid acids, namely melamine-(H2SO4)3 and melamine-(HNO3)3. Mixture of them acts as a unique powerful system instead of a hazardous H2SO4/HNO3 system for the direct oxidation of thiols. Also, this system can oxidize the sulfides in the presence of a catalytic amount of KBr and few drops of water. This procedure offers advantages such as very low reaction time, simple work-up, excellent yield and matching with some green chemistry protocols.
- Chehardoli, Gholamabbas,Zolfigol, Mohammad Ali
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p. 606 - 612
(2015/11/17)
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- Evans hole and non linear optical activity in Bis(melaminium) sulphate dihydrate: A vibrational spectral study
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Bis(melaminium) sulphate dihydrate (BMSD), an interesting melaminium derivative for nonlinear optical activity, has been subjected to vibrational spectral analysis using FT IR and FT Raman spectra. The analysis has been aided by the Potential Energy Distribution (PED) of vibrational spectral bands, derived using density functional theory (DFT) at B3LYP/6-31G(d) level. The geometry is found to correlate well with the XRD structure and the band profiles for certain vibrations in the finger print region have been theoretically explained using Evans hole. The detailed Natural Bond Orbital (NBO) analysis of the hydrogen bonding in BMSD has also been carried out to understand the correlation between the stabilization energy of hyperconjugation of the lone pair of donor with the σ? orbital of hydrogen-acceptor bond and the strength of hydrogen bond. The theoretical calculation shows that BMSD has NLO efficiency, 2.66 times that of urea. The frontier molecular orbital analysis points to a charge transfer, which contributes to NLO activity, through N-H...O intermolecular hydrogen bonding between the melaminium ring and the sulphate. The molecular electrostatic potential (MEP) mapping has also been performed for the detailed analysis of the mutual interactions between melaminium ring and sulphate ion.
- Suresh Kumar,Binoy,Dawn Dharma Roy,Marchewka,Jayakumar
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p. 292 - 301
(2015/12/01)
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- A template induced method to synthesize nanoporous graphitic carbon nitride with enhanced photocatalytic activity under visible light
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A template induced method was developed to synthesize nanoporous graphitic carbon nitride (npg-CN) by directly heating Triton X-100-modified-melamine sulfate. The effects of the added amount of Triton X-100 and heating temperature on the formation of npg-CN were investigated. The npg-CN samples were characterized by XRD, FT-IR, and elemental analysis; nitrogen adsorption isotherms, SEM and TEM images; and UV-vis DRS and photoluminescence spectra. The results showed that the npg-CN samples possessed a laver-like layered structure with a high surface area (50-135 m2 g-1). Meanwhile, compared to the bulk g-CN (synthesized by directly heating melamine), the npg-CN samples possessed stronger optical absorptions, narrower band gaps, and significantly reduced fluorescence intensity. The photocatalytic activity was investigated by degradation of Rhodamine B under visible light irradiation. As a result, the photodegradation rate of Rhodamine B dye on the npg-CN samples was greatly improved over that on bulk g-CN.
- Fan, Qianjing,Liu, Jianjun,Yu, Yingchun,Zuo, Shengli
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p. 61877 - 61883
(2015/02/19)
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- The influence of hydrogen bonding on the planar arrangement of melamine in crystal structures of its solvates, cocrystals and salts
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The hydrogen bonding patterns of melamine as well as mono- and diprotonated melamine have been analysed in five crystal structures of a solvate, a cocrystal and three organic and inorganic salts, namely, melamine DMSO solvate ([mel]·DMSO (1)), melamine theobromine cocrystal ([mel]·[TBR] 3 (2)), dimelaminium ethylenediaminetetraacetate ([mel-H] 2[EDTA-H2]·2H2O (3)), anhydrous dimelaminium sulfate ([mel-H]2[SO4] (4)), and anhydrous melaminium dinitrate ([mel-H2][NO3]2 (5)). Melamine is a versatile molecular building block (tecton) in cocrystals, solvates and salts. Depending on the degree of protonation and/or other molecules or ions present in the structure, parallels could be drawn to determine whether melamine is arranged in a cross-linked manner, in undulating sheets or in the form of perfectly planar sheets in the structure. Graph set analysis was used to compare the geometry of hydrogen bond interactions of the new structures with those of other structures published in the literature. Solvent drop-assisted solid state reactions (kneading) were performed for green synthesis of the compounds. The organic salt 3 has high thermal stability as shown by variable-temperature X-ray powder diffraction, which is presumably related to its extensive hydrogen bond network. Rietveld refinements were carried out on laboratory powder diffraction data to confirm the structures of the compounds obtained from single-crystal data. This journal is the Partner Organisations 2014.
- Vella-Zarb, Liana,Braga, Dario,Guy Orpen,Baisch, Ulrich
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p. 8147 - 8159
(2014/11/27)
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- Melamine-(H2SO4)3 and PVP-(H 2SO4)n as solid acids: Synthesis and application in the first mono- and di-nitration of bisphenol A and other phenols
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Melamine and poly vinylpyrrolidone (PVP) reacted with neat sulfuric acid readily to form two new organic solid acids namely melamine-(H 2SO4)3 and PVP-(H2SO 4)n. These solid acids were used for the first nitration of bisphenol A as well as other phenols in the presence of NH4NO 3. Mono- and di-nitro bisphenol A have been characterized with IR and 1H NMR techniques.
- Chehardoli, Gholamabbas,Zolfigol, Mohammad Ali,Azimi, Seyedeh Bahareh,Alizadeh, Ebadollah
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experimental part
p. 827 - 830
(2012/02/14)
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