Molecular crystals, decompositions

Molecular weight Decomposition temperature/°C Thermal ignition temperature/°C Crystal density at 20 °C/g cm 3 Energy of formation/kJ kg 1 Enthalpy of formation/kJ kg... 

Decomposition of molecular crystals below their melting points requires that the stability of the molecules be lower than the intermolecular forces in the crystals. 

Hydrate crystal decomposition, like the hydrate growth, is a deterministic process. Hence, the process is amenable to study experimentally and modeling. Although some studies have been undertaken at the molecular level, most of them on the hydrate decomposition kinetics are based on a macroscopic approach. The hydrate decomposition is a heterogeneous process where liquid water and gas are released as the solid... 

B.G. and Jeong, J.H. (2006) Synthesis of Cu nanopartides prepared by using thermal decomposition of Cu-oleate complex. Molecular Crystals and Liquid Crystals, 445, 231-8. 

Heath and Majer (H3) have recently used a mass spectrometer to study the decomposition of ammonium perchlorate. Decomposition was detected in the range from 110° to 120°C. At this temperature, there were ions in the mass spectrum caused by NH3, HC104, Cl2, HC1, nitrogen oxides, and 02. The appearance of the species NO, N02,02, and Cl2 in the decomposition products under very low pressure (i.e., in the absence of gas-phase molecular collisions) indicates that the principal decomposition reactions take place in the crystal and not in the gas phase. 

For 2,3,4,6-tetrachlorophenol hardly any discoloration was detected above 200°C instead the sample vaporized rapidly. Its sodium salt reacted similarly to sodium pentachlorophenate except that its exothermic decomposition (Figure 4) is less clearly defined no crystallization occurred on cooling, and the yield of hexachlorodioxins was much lower, the remaining products being higher molecular weight materials. The hexachlorodioxins were identified by gas-liquid chromatography as two isomers in a ratio of 35 65. 

Unac, R. O., Bustos, V., Wilson, J. et al. (2006) Molecular beam measurements and Monte Carlo simulations of the kinetics of N20 decomposition on Rh(l 11) single-crystal surfaces , J. Chem. Phys., 125, 074705-1. 

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