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In principle chemical reactions can ber induced by high pressure. Many reactions also can be induced by photolysis. Researchers have now worked out a method that takes advantage of both phenomena. Group has been using FTIR spectroscopy to monitor the behavior of unsaturated compds under pressure in a diamond anvil cell. In their latest work, the researchers observe that butadiene dimerizes over several days at 0.7 gigapascal, primarily producing vinylcyclohexene via cycloaddition. But when the pressurized sample is irradiated with a 488-nm laser beam, dimerization is completely inhibited & highly stereoregular trans-polybutadiene is formed in quantitative yield. Generally butadiene polymn is a high-T catalytic process that results in a mix of both trans & cis isomers. In the new experiments, author believes that the pressure forces the molecules to align & that the laser light selectively directs them into a specific electronic state that leads to the polymer. Increasing the light energy should allow faster reactions at lower pressures, potentially leading to practical green chemistry "without the use of solvents, catalysts & radical initiators"
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