Fluoroalkene chemistry: Part 1. Highly-toxic fluorobutenes and their mode of toxicity: reactions of perfluoroisobutene and polyfluorinated cyclobutenes with thiols

The reactions of four highly-toxic fluorobutenes - perfluoroisobutene (PFIB), 1-hydropentafluorocyclobutene (1-H), hexafluorocyclobutene (HFCB) and 3-chloropentafluorocyclobutene (3-Cl)—with propanethiol, 2,6-dimethoxybenzenethiol and N-acetylcysteine isopropyl ester were studied. PFIB and HFCB reacted with two molar equivalents of the aliphatic thiols, but with only one molar equivalent of the aromatic thiol (presumably due to steric hindrance) and resembled phosgene in their reactivity. The fluorocyclobutenes 1-H and 3-Cl reacted with one and up to three molar equivalents of the aliphatic thiols, respectively, but with only one molar equivalent of the aromatic thiol. The products of allyl and vinyl substitution were isolated and characterised as fully as possible. The inhalation toxicities of the fluorocyclobutenes to rodents correlated with the number of easily-displaceable fluorine substituents, supporting the contention that toxicity is due to reaction with biological thiols in the lung.     

Fluoroalkene chemistry: Part 3. Reactions of arylthiols with perfluoroisobutene, perfluoropropene and chlorotrifluoroethene

Reactions of perfluoroisobutene (PFIB), perfluoropropene (PFP) and chlorotrifluoroethene (CTFE) with benzenethiol and 2-methoxybenzenethiol in acetonitrile, with potassium carbonate as base, were compared. PFIB reacted with benzenethiol to give ketene thioacetal (CF₃)₂CC(SAr)₂ and with 2-methoxybenzenethiol to give mono- and bis-vinyl species (CF₃)₂CCFSAr and (CF₃)₂CC(SAr)₂. PFP reacted with both thiols to give the addition product CF₃CFHCF₂SAr and vinyl isomers CF₃CFCFSAr (6:1 E/Z ratio). CTFE reacted with several methoxy-substituted arylthiols to give addition products of structure CFClHCF₂SAr. The arylthiols used throughout the study imitate biological thiols. Inhalation toxicities of the fluoroalkenes decrease in the order PFIB > PFP > CTFE and correlate with their reactivities towards the model thiols, supporting the current view that their toxicity relates to their ability to react with biological thiols.     

Semi-empirical AM1 study on the hydrolysis reactions of perfluoroisobutene in the gas phase

The hydrolysis of perfluoroisobutene to 2H-hexafluoroisobutyric acid in the gas phase has been studied using semi-empirical AM1 calculations on the products and postulated reaction intermediates. Reaction enthalpies have been calculated from computed heats of formation in order to find the energetically most favoured reaction pathway. The deprotonation reactions of the intermediate structures have been studied using AM1 reaction enthalpies. An energetically favoured reaction sequence for the hydrolysis of perfluoroisobutene is derived which accounts for the observed products. The remaining ambiguities in this reaction mechanism are indicated.     

活性炭的高温脱氧改性及其床层对全氟异丁烯的吸附动力学研究

在N2气保护下对颗粒状活性炭进行了不同温度(400—800 ℃)下的高温改性, 考察了不同的空气流湿度(30%—80% R.H.)下全氟异丁烯(PFIB)在活性炭床层中的吸附穿透行为. 利用Wheeler方程对穿透数据进行了处理, 并采用线性平衡吸附体系的动力学模型对床层的穿透实验数据进行了关联. 结果表明, 基炭经高温改性后, 活性炭的孔隙结构没有明显变化, 表面含氧量随处理温度的提高而减少, 在高湿条件下对全氟异丁烯的选择性吸附能力显著提高, 活性炭床层可使PFIB的防护时间延长. 各种实验条件下的理论穿透曲线与实验值数据吻合, 可以利用线性平衡吸附体系的动力学模型来预示PFIB在活性炭层中的穿透行为, 进行防毒面具的滤毒罐参数的选取和设计.