62572-83-2Relevant articles and documents
The influence of hydrogen bonding on the planar arrangement of melamine in crystal structures of its solvates, cocrystals and salts
Vella-Zarb, Liana,Braga, Dario,Guy Orpen,Baisch, Ulrich
, p. 8147 - 8159 (2014)
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.
Evans hole and non linear optical activity in Bis(melaminium) sulphate dihydrate: A vibrational spectral study
Suresh Kumar,Binoy,Dawn Dharma Roy,Marchewka,Jayakumar
, p. 292 - 301 (2015)
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.
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
Chehardoli, Gholamabbas,Zolfigol, Mohammad Ali
, p. 606 - 612 (2015/11/17)
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.
