文摘
The rate of the transfer of deuterium from to the three types (benzylic, aliphatic and aromatic) of bonds of 2-Ethylnaphthalene (and Methylnaphthalene) has been measured in the laboratory. The D/H ratio of each bond was calculated from the mass spectrum of the different isotopomers produced in the source of the GC mass spectrometer. The relations between the D/H ratio of the different isotopomers allow to calculate the internal isotopic fractionation factors (¦Ái?i>j = (D/H)i/(D/H)j) between the 3 bonds: ¦ÁBenzylic¨CAromatic = 1.99 ¡À 0.38 and ¦ÁAliphatic¨CAromatic = 1.22 ¡À 0.39. Isotopic exchange rate constants are ?.2 ¡Á 10?¡À0.4 s?, determined at room temperature for 10? g of 2-Ethylnaphthalene in contact with 5 ¡Á 1012 cm? of . These results are compatible with those measured in the insoluble organic matter (IOM) isolated from the Orgueil meteorite (), i.e., ¦ÁBenzylic¨CAromatic = 1.96 ¡À 0.05 and ¦ÁAliphatic¨CAromatic = 1.35 ¡À 0.05. Using the calculated dust and H2D+ densities from the models of deuterium chemistry in protostellar disks, the duration needed to enrich the IOM up to its measured D/H ratio is ?04¡À1 s. These laboratory results are in agreement with a late deuteration of the insoluble organic matter taking place in the solar T-Tauri disk by interaction of the organic dust with H2D+.