European Laboratory for Nonlinear Spectroscopy (LENS), via Nello Carrara 1, 50019 Sesto Fiorentino, Italia.
J Phys Chem B. 2010 Jul 29;114(29):9420-8. doi: 10.1021/jp1035508.
The room-temperature pressure-induced reaction of nitromethane has been studied by means of infrared spectroscopy in conjunction with ab initio molecular dynamics simulations. The evolution of the IR spectrum during the reaction has been monitored at 32.2 and 35.5 GPa performing the measurements in a diamond anvil cell. The simulations allowed the characterization of the onset of the high-pressure reaction, showing that its mechanism has a complex bimolecular character and involves the formation of the aci-ion of nitromethane. The growth of a three-dimensional disordered polymer has been evidenced both in the experiments and in the simulations. On decompression of the sample, after the reaction, a continuous evolution of the product is observed with a decomposition into smaller molecules. This behavior has been confirmed by the simulations and represents an important novelty in the scene of the known high-pressure reactions of molecular systems. The major reaction product on decompression is N-methylformamide, the smallest molecule containing the peptide bond. The high-pressure reaction of crystalline nitromethane under irradiation at 458 nm was also experimentally studied. The reaction threshold pressure is significantly lowered by the electronic excitation through two-photon absorption, and methanol, not detected in the purely pressure-induced reaction, is formed. The presence of ammonium carbonate is also observed.
室温下加压条件下的硝基甲烷反应已经通过结合红外光谱和从头算分子动力学模拟进行了研究。在金刚石压腔中，在 32.2 和 35.5 GPa 下进行测量，监测了反应过程中红外光谱的演化。模拟允许对高压反应的起始进行特征描述，表明其机制具有复杂的双分子特征，并涉及硝基甲烷的酸离子的形成。在实验和模拟中都证明了三维无序聚合物的生长。在样品减压后，反应后，观察到产物连续演化，并分解成较小的分子。这种行为已被模拟所证实，代表了已知分子体系高压反应领域的一个重要新发现。在减压过程中，主要的反应产物是 N-甲基甲酰胺，这是含有肽键的最小分子。通过双光子吸收进行电子激发还实验研究了结晶硝基甲烷的高压反应。反应的阈值压力通过电子激发显著降低，并且在纯压力诱导反应中未检测到甲醇形成。还观察到碳酸铵的存在。
