Perfluorohexyl-ethane

We have studied the hydrogenolysis of 2-(perfluorohexyl)ethane thiocyanate to 2-(perfluorohexyl)ethane thiol. It was discovered that perfluoroalkyl thiocyanates can be reduced to thiols and co-product hydrogen cyanide with molecular hydrogen in the presence of a carbon-supported palladium-tin catalyst. This result is surprising since it is known that palladium and other gronps 8 to 10 metal catalysts are poisoned by the product thiol, traces of hydrogen snlfide byprodnct, and the hydrogen cyanide co-product. For that reason, we characterized the catalyst to understand why it was so robust under conditions that would normally poison snch a catalyst. 

Perfluoroalkyl)ethane thiols have been used as precursors to fluorinated surfactants and products for hydro- and oligophobic finishing of substrates such as textiles and leather (1). The synthesis of 2-(perfluoroalkyl)ethane thiol and a byproduct bis-(-2-perfluoroalkylethane)-disulfide (5-10%) has been practiced via the reaction of 2-(perfluoroalkyl)ethane iodide with thiourea to form an isothiuronium salt which is cleaved with alkali or high molecular weight amine as shown in Equation 1 for 2-(perfluorohexyl)ethane iodide (1). 

Nucleophihc substitution of sodium thiolate on 2-(perfluorohexyl)ethane iodide leads to extensive elimination (10-20%) and formation of (perfluorohexyl)ethylene (3), Equation 2. 

It has been known for many years that 2-(perfluorohexyl)ethane thiocyanate can be synthesized in qnantitative yields from 2-(perfluorohexyl)ethane iodide (4), as shown in Equation 3. 

Perfluorohexyl)ethane iodide was obtained from the Surface Protection Solntions business at DuPont. Sodinm thiocyanate was purchased from Aldrich and nsed without further purificatiom The 2-(perfluorohexyl)ethane iodide was converted to... 

Abbreviations Bdmpe[l,l-Bis(3,4-dimethylphenyl)ethane] Pfhethiol (2-perfluorohexyl)ethane thiol). 

Perfluoro- decalin Perfluo- rooctane Perfluorohexyl- ethane Perfluorobutyl- butane... 

All compounds used had equivalent purity (see Table 11). The test design was focused on the evaluation of histological differences after a tamponade time of 6 weeks. The density of the PFCLs used was 1.32 g/ml (perfluorobutylbutane), 1.62 g/ml (perfluorohexyl-ethane) and 1.78 g/ml (PFO). There was no dose-response relationship that means there is no evidence that a higher density creates more severe histological damage. Therefore, the simple explanation of the insufficient long-term tolerance for PFCLs could not be verified. 

Our own investigations concentrated on compounds with different densities (PFO and perfluorohexyl-ethane) and additionally on compounds with comparable densities but different viscosities. Perfluorohexyl-ethane was tested as a monomer and in two oligomeric configurations with the same molecular unit but... 

Bis(perfluoro-n-butyl)ethene (F-44E) can be obtained from pure products, n-butyl iodide and ethylene, by a two-step process [6,42,86]. The double bond of the molecule has raised the question of chemical stability, but in biological conditions, no evidence of chemical reactions has been found. Animal tests have indicated satisfactory biocompatibility. Bis(perfluorohexyl)ethane (F-66E), however, has caused some toxic effects [85]. 

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