作者:Ronald Brown、Anne S. Dolan、Charles Kemball、Gordon S. McDougall
DOI:10.1039/ft9928802405
日期:——
The exchange reaction of methylcyclopentane with deuterium has been carried out over supported palladium, platinum and rhodium catalysts and the products analysed by mass spectrometry and deuterium NMR spectroscopy. The NMR resonances for the deuterium in the six positions in the molecule were well separated and each could be resolved into two or more components as a consequence of the isotopic shifts due to the presence of neighbouring deuterium atoms.It was possible to determine the fractions of the molecules exchanged on the open side of the ring, on the hindered side (cis to the methyl group) or on both sides. These fractions and other features of the experimental results were used to discuss the mechanisms of the exchange reactions and the manner in which these varied with the metal or with temperature. The highest extents of multiple exchange and of ‘turnover’ of the molecules on the surface were found with palladium.
甲基环戊烷与氘的交换反应已在负载型的钯、铂和铑催化剂上进行,产物用质谱和氘的核磁共振波谱进行了分析。这两种方法获得的氘在分子中六个位置上的核磁共振谱线彼此分隔得很好,而且每一条谱线根据附近有氘原子时由于同位素移动而造成的影响,都可以被分解成两个或更多的组份。这样就有可能确定在开环一侧、在立体阻碍的一侧(与甲基处于顺式)或两边进行的置换的份额。把这些份额以及实验结果的其它特点用来讨论交换反应的机理以及随着金属或温度的变化这些反应机理所起的变化。钯催化剂获得最高程度的多次交换以及分子在表面上最大程度的“周转”。