Parsons Brendon A, Smith Olivia Lin, Chae Myeong, Dragojlovic Veljko
Wilkes Honors College of Florida Atlantic University, 5353 Parkside Drive, Jupiter, FL 33458, USA ; Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195-1700, USA.
Wilkes Honors College of Florida Atlantic University, 5353 Parkside Drive, Jupiter, FL 33458, USA.
Beilstein J Org Chem. 2015 Jun 9;11:980-93. doi: 10.3762/bjoc.11.110. eCollection 2015.
In a PTFE tape phase-vanishing reaction (PV-PTFE), a delivery tube sealed with PTFE tape is inserted into a vessel which contains the substrate. The reagent diffuses across the PTFE tape barrier into the reaction vessel. PTFE co-polymer films have been found to exhibit selective permeability towards organic compounds, which was affected by the presence of solvents. In this study, we attempted to establish general trends of permeability of PTFE tape to different compounds and to better describe the process of solvent transport in PV-PTFE bromination reactions. Though PTFE tape has been reported as impermeable to some compounds, such as dimethyl phthalate, solvent adsorption to the tape altered its permeability and allowed diffusion through channels of solvent within the PTFE tape. In this case, the solvent-filled pores of the PTFE tape are chemically more akin to the adsorbed solvent rather than to the PTFE fluorous structure. The solvent uptake effect, which was frequently observed in the course of PV-PTFE reactions, can be related to the surface tension of the solvent and the polarity of the solvent relative to the reagent. The lack of pores in bulk PTFE prevents solvents from altering its permeability and, therefore, bulk PTFE is impermeable to most solvents and reagents. However, bromine, which is soluble in liquid fluorous media, diffused through the bulk PTFE. A better understanding of the PTFE phase barrier will make it possible to further optimize the PV-PTFE reaction design.
在聚四氟乙烯胶带相消失反应（PV - PTFE）中，一根用聚四氟乙烯胶带密封的输送管插入装有底物的容器中。试剂通过聚四氟乙烯胶带屏障扩散到反应容器中。已发现聚四氟乙烯共聚物薄膜对有机化合物表现出选择性渗透性，这受溶剂存在的影响。在本研究中，我们试图确定聚四氟乙烯胶带对不同化合物的渗透一般趋势，并更好地描述PV - PTFE溴化反应中溶剂传输过程。尽管已报道聚四氟乙烯胶带对某些化合物（如邻苯二甲酸二甲酯）不可渗透，但溶剂在胶带上的吸附改变了其渗透性，并允许通过聚四氟乙烯胶带内的溶剂通道扩散。在这种情况下，聚四氟乙烯胶带充满溶剂的孔隙在化学性质上更类似于吸附的溶剂，而不是聚四氟乙烯含氟结构。在PV - PTFE反应过程中经常观察到的溶剂吸收效应，可能与溶剂的表面张力以及溶剂相对于试剂的极性有关。块状聚四氟乙烯中缺乏孔隙可防止溶剂改变其渗透性，因此，块状聚四氟乙烯对大多数溶剂和试剂是不可渗透的。然而，可溶于液态含氟介质的溴通过块状聚四氟乙烯扩散。更好地理解聚四氟乙烯相屏障将使进一步优化PV - PTFE反应设计成为可能。
