Perfluorobutanesulfonyl Fluoride Research Articles

Potential toxic effects of perfluorobutanesulfonyl fluoride analysis based on multiple-spectroscopy techniques and molecular modelling analysis

Perfluorobutanesulfonyl fluoride (PBSF) has been used in the manufacture of fluorochemicals. Since PBSF is not biodegradable, the predicted environmental levels of PBSF are also expected to rise over time. In recent years, there has been a rise in the levels of PBSF in humans. In order to clarify the impact of PBSF on the accumulation of substances in the human body, we examined the interaction mechanism between PBSF and bovine serum albumin (BSA). To investigate the interaction mechanism between PBSF and BSA, we utilized a range of methods including UV–visible spectrophotometry, fluorescence spectroscopy, circular dichroism, molecular docking simulation, and molecular dynamics (MD) simulation. The inherent fluorescence of BSA was effectively suppressed by PBSF through fluorescence quenching analysis, using a static mechanism. The Ka value of 1.34 × 105 mol−1 L indicated a strong binding between PBSF and BSA. Further analysis of the interaction between PBSF and BSA involved examining thermodynamic parameters, fluorescence resonance energy transfer, and conducting other theoretical calculations. These investigations produced results that were in strong accordance with the experimental observations. The participation of hydrophobic interactions between BSA and PBSF was uncovered through molecular docking and MD simulation investigations. Furthermore, this investigation explored the impact of copper ions (Cu2+) and calcium ions (Ca2+) on the interaction between PBSF and BSA, establishing a vital basis for comprehending the mechanism by which PBSF affects proteins in the human surroundings.

Synthesis of Chiral Tertiary Allylic- and Propargylic Fluorides from Nonaflates of Chiral α-Fluorinated β-Keto Dicarbonyl Compounds.

The acetyl group of chiral α-fluorinated dicarbonyl compounds was transformed to nonaflates through a reaction with perfluorobutanesulfonyl fluoride in the presence of DBU in 82-95% yield. These nonaflates were used in Suzuki and Sonogashira coupling reactions to afford chiral tertiary allylic fluorides bearing gem-disubstituted terminal alkenes with excellent optical purities (45-91%, ≥94% ee). In addition, chiral tertiary propargylic fluorides were obtained from the reaction of nonaflates with DBU (73-86%, ≥94% ee).

Sensing performance of CuO/Cu2O/ZnO:Fe heterostructure coated with thermally stable ultrathin hydrophobic PV3D3 polymer layer for battery application

Gas sensors are demanded in many different application fields. Especially the ever-growing field of batteries creates a great need for early hazard detection by gas sensors. Metal oxides are well known for gas sensing; however, moisture continues to be a major problem for the sensors, especially for the application in battery systems. This study reports on a new type of moisture protected gas sensor, which is capable to solve this problem. Sensitive nano-materials of CuO/Cu2O/ZnO:Fe heterostructures are grown and subsequently coated with an ultrathin hydrophobic cyclosiloxane-polymer film via initiated chemical vapor deposition to protect the sensor from moisture. The monomer 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane is combined with the initiator perfluorobutanesulfonyl fluoride to obtain hydrophobic properties. Surface chemistry, film formation and preservation of functional groups are confirmed by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. It turns out that the hydrophobicity is retained even after annealing at 400 °C, which is ideal for gas sensing. Molecular distances in the polymer nanolayer are estimated by geometry optimization via MMFF94 followed by density functional theory. Compared with unprotected CuO/Cu2O/ZnO:Fe, the coated CuO/Cu2O/ZnO:Fe exhibit a much better sensing performance at a higher relative humidity, as well as tunability of the gas selectivity. This is highly beneficial for hazard detection in case of thermal runaway in batteries because the sensors can be used under high concentrations of relative humidity, which is ideal for Li–S battery applications.

Deoxyfluorination of (Hetero)aryl Aldehydes Using Tetramethylammonium Fluoride and Perfluorobutanesulfonyl Fluoride or Trifluoromethanesulfonic Anhydride

AbstractThis Communication describes the conversion of (hetero)aryl aldehydes into the corresponding (hetero)aryl difluoromethyl products using anhydrous NMe4F in combination with perfluorobutanesulfonyl fluoride or trifluoromethanesulfonic anhydride.

Rapid Deoxyfluorination of Alcohols with N-Tosyl-4-chlorobenzenesulfonimidoyl Fluoride (SulfoxFluor) at Room Temperature.

The deoxyfluorination of alcohols is a fundamentally important approach to access alkyl fluorides, and thus the development of shelf-stable, easy-to-handle, fluorine-economical, and highly selective deoxyfluorination reagents is highly desired. This work describes the development of a crystalline compound, N-tosyl-4-chlorobenzenesulfonimidoyl fluoride (SulfoxFluor), as a novel deoxyfluorination reagent that possesses all of the aforementioned merits, which is rare in the arena of deoxyfluorination. Endowed by the multi-dimensional modulating ability of the sulfonimidoyl group, SulfoxFluor is superior to 2-pyridinesulfonyl fluoride (PyFluor) in fluorination rate, and is also superior to perfluorobutanesulfonyl fluoride (PBSF) in fluorine-economy. Its reaction with alcohols not only tolerates a wide range of functionalities including the more sterically hindered alcoholic hydroxyl groups, but also exhibits high fluorination/elimination selectivity. Because SulfoxFluor can be easily prepared from inexpensive materials and can be safely handled without special techniques, it promises to serve as a practical deoxyfluorination reagent for the synthesis of various alkyl fluorides.

Perfluoroalkane sulfonyl fluorides non-covalently bind to human serum albumin at Sudlow’s sites

Perfluorooctane sulfonyl fluoride (PFOSF) has been defined as persistent organic pollutant in the Stockholm Convention in 2009. Currently PFOSF and its substitutes (structural analogues in which octyl group is substituted for other aliphatic chains) are still scarcely studied. HSA is a main carrier for drugs in blood, and the influence of exogenous compounds including pollutants on HSA is of particular interest. In this work, the binding sites of HSA to Perfluoroalkane sulfonyl fluoride (PFASFs) were determined by fluorescence technique. The results demonstrated that PFASFs competitively bind to HSA at Sudlow’s site I against warfarin and at Sudlow’s site II against dansyl-proline and the related association constants were determined. The association constants of PFOSF, perfluorohexane sulfonyl fluoride (PFHSF) and perfluorobutane sulfonyl fluoride (PFBSF) were determined to be 2.59 × 10−3 μM-1, 4.65 × 10−3 μM-1 and 2.85 × 10−3 μM-1 at Sudlow’s site I and 8.68 × 10−4 μM-1, 3.43 × 10−2 μM-1 and 1.92 × 10−2 μM-1 at Sudlow’s site II, respectively. The results showed that PFASFs can bind tightly to HSA and thus migrate to all parts of the body through vascular system. Non-covalent interaction between HSA and PFASFs was confirmed with tryptic digestion experiment. The mass spectra results indicated that other binding sites of HSA are also involved in the binding of PFHSF and PFBSF. The total binding numbers of PFOSF, PFHSF and PFBSF on HSA are 2, 6 and 3, respectively.

Global emission inventories for C4–C14 perfluoroalkyl carboxylic acid (PFCA) homologues from 1951 to 2030, part II: The remaining pieces of the puzzle

We identify eleven emission sources of perfluoroalkyl carboxylic acids (PFCAs) that have not been discussed in the past. These sources can be divided into three groups: [i] PFCAs released as ingredients or impurities, e.g., historical and current use of perfluorobutanoic acid (PFBA), perfluorohexanoic acid (PFHxA) and their derivatives; [ii] PFCAs formed as degradation products, e.g., atmospheric degradation of some hydrofluorocarbons (HFCs) and hydrofluoroethers (HFEs); and [iii] sources from which PFCAs are released as both impurities and degradation products, e.g., historical and current use of perfluorobutane sulfonyl fluoride (PBSF)- and perfluorohexane sulfonyl fluoride (PHxSF)-based products. Available information confirms that these sources were active in the past or are still active today, but due to a lack of information, it is not yet possible to quantify emissions from these sources. However, our review of the available information on these sources shows that some of the sources may have been significant in the past (e.g., the historical use of PFBA-, PFHxA-, PBSF- and PHxSF-based products), whereas others can be significant in the long-term (e.g., (bio)degradation of various side-chain fluorinated polymers where PFCA precursors are chemically bound to the backbone). In addition, we summarize critical knowledge and data gaps regarding these sources as a basis for future research.

Synthesis and Performance of Novel Fluorinated Acrylate Polymers: Preparation and Reactivity of Short Perfluoroalkyl Group Containing Monomers

Developing novel fluorinated monomers and polymer materials with a short perfluoroalkyl group is attracting the attention of researchers. The synthesis of fluorinated monomers, [N-methyl-perfluorobutane-1-sulfonamide]ethyl acrylate (C4SA) and methacrylate (C4SMA), [N-methyl-perfluorohexane-1-sulfonamide]ethyl acrylate (C6SA), and methacrylate (C6SMA) were presented from a three-step procedure, which combined the reaction of perfluorobutanesulfonyl fluoride or perfluorohexanesulfonyl fluoride with an excess of methylamine, alkylation reaction with 2-bromoethanol, and esterification reaction with acryloyl chloride or methacryloyl chloride. The outcome compounds structures of each step were confirmed by 1H NMR, 19F NMR, FT-IR, and elemental analysis. Free radical copolymerizations of fluorinated acrylates and butyl methacrylate (BMA) in butyl acetate (BuOAc) were performed to determine the comonomers reactivity ratios and Q-e values. The surface wetting properties of fluorinated homopolymers were investigated by surface tension and dynamic contact angles. As a result, the target polymers showed extreme low surface energies and dynamic surface properties.

Tissue distribution of 35S-labelled perfluorobutanesulfonic acid in adult mice following dietary exposure for 1–5 days

Perfluorobutanesulfonyl fluoride (PBSF) has been introduced as a replacement for its eight-carbon homolog perfluorooctanesulfonyl fluoride (POSF) in the manufacturing of fluorochemicals. Fluorochemicals derived from PBSF may give rise to perfluorobutanesulfonic acid (PFBS) as a terminal degradation product. Although basic mammalian toxicokinetic data exist for PFBS, information on its tissue distribution has only been reported in one study focused on rat liver. Therefore, here we characterized the tissue distribution of PFBS in mice in the same manner as we earlier examined its eight-carbon homolog perfluorooctanesulfonate (PFOS) to allow direct comparisons. Following dietary exposure of adult male C57/BL6 mice for 1, 3 or 5d to 16mg 35S-PFBSkg−1d−1, both scintillation counting and whole-body autoradiography (WBA) revealed the presence of PFBS in all of the 20 different tissues examined, demonstrating its ability to leave the bloodstream and enter tissues. After 5d of treatment the highest levels were detected in liver, gastrointestinal tract, blood, kidney, cartilage, whole bone, lungs and thyroid gland. WBA revealed relatively high levels of PFBS in male genital organs as well, with the exception of the testis. The tissue levels increased from 1 to 3d of exposure but appeared thereafter to level-off in most cases. The estimated major body compartments were whole bone, liver, blood, skin and muscle. This exposure to PFBS resulted in 5–40-fold lower tissue levels than did similar exposure to PFOS, as well as in a different pattern of tissue distribution, including lower levels in liver and lungs relative to blood.

氟烷磺酰氟／双氧水／碱／丙酮体系与苄醇衍生物的氧化反应

研究了氟烷磺酰氟／双氧水／氢氧化钠／丙酮体系与6个苄醇衍生物的氧化反应，其中氟烷磺酰氟包括HCF2CF2OCF2CF2SO2F，n-C4F9S02F和n-C8F12SO2F．最优反应条件为n（苄醇衍生物）：n（氟烷磺酰氟）：n（双氧水）：n（氢氧化钠）=1：4：8：8，溶剂为丙酮，反应温度为20℃，反应时间为24h．产物酮的收率为23％-92％．探讨了该氧化反应的机理，原位生成的氟烷基过氧磺酸中间体可将丙酮氧化为二甲基二氧杂环丙烷，进而将反应体系中共存的苄醇衍生物氧化成相应的产物酮．氟烷磺酰氟／双氧水／氢氧化钠／丙酮体系原位生成的二甲基二氧杂环丙烷氧化苄位羟基的能力和传统的Oxone／CH3COCH3体系相当．本研究提供了一种新颖的原位制备二甲基二氧杂环丙烷的方法．

ChemInform Abstract: Total Syntheses of (Sp)‐(+)‐ and (Rp)‐(‐)‐Spiniferin‐1, a Pair of Unusual Natural Products with Planar Chirality

Abstractvia a palladium‐catalyzed β‐H elimination reaction of ester (I) and a perfluorobutanesulfonyl fluoride induced homoallylic carbocation rearrangement as key steps

A two-generation oral gavage reproduction study with potassium perfluorobutanesulfonate (K +PFBS) in Sprague Dawley rats

Perfluorobutanesulfonate (PFBS) is a surfactant and degradation product of substances based on perfluorobutanesulfonyl fluoride. A two-generation reproductive rat study has been conducted with potassium PFBS (K +PFBS). Parental-generation (P) rats were dosed orally by gavage with 0, 30, 100, 300 and 1000 mg K +PFBS/kg/day for 10 weeks prior to and through mating (males and females), as well as during gestation and lactation (females only). First generation (F1) pups were dosed similarly, beginning at weaning. Second generation (F2) pups were not directly dosed but potentially exposed to PFBS through placental transfer and nursing, and the study was terminated 3 weeks after their birth. Endpoints evaluated included body weight, food consumption, clinical signs, estrus cycling, sperm quality, pregnancy, natural delivery, litter outcomes, and developmental landmarks. The no-observable-adverse effect dose level (NOAEL) in the parental generations (P and F1) was 100 mg/kg/day. In the 300 and 1000 mg/kg/day dose group rats, there were (1) increased liver weight (absolute or relative) and corresponding increased incidence of adaptive hepatocellular hypertrophy (male only) and (2) increased incidence of minimal to mild microscopic findings in the medulla and papilla of the kidneys (male and female). There were no K +PFBS treatment-related effects on fertility or reproduction among the P or the F1 rats. There were no microscopic changes in male or female reproductive organs, and no biologically relevant effects on sperm parameters, mating, estrous cycles, pregnancy, and natural delivery in the P- or F1-generations. There were no K +PFBS treatment-related effects on survival of pups in the two-generation study. Litter size and average pup birth weight per litter were not statistically significantly different from controls in any dose group. In the F1-generation, terminal body weight was reduced in males at 1000 mg/kg/day. Preputial separation was slightly delayed (approximately 2 days) at this dose, a finding consistent with the body weight reduction. Essentially no effects were observed in the F1 females. F2 pups had normal body weights. The reproductive NOAEL was >1000 mg/kg/day in both generations.

A comparison of the pharmacokinetics of perfluorobutanesulfonate (PFBS) in rats, monkeys, and humans

Materials derived from perfluorobutanesulfonyl fluoride (PBSF, C 4F 9SO 2F) have been introduced as replacements for eight-carbon homolog products that were manufactured from perfluorooctanesulfonyl fluoride (POSF, C 8F 17SO 2F). Perfluorobutanesulfonate (PFBS, C 4F 9SO 3 −) is a surfactant and potential degradation product of PBSF-derived materials. The purpose of this series of studies was to evaluate the pharmacokinetics of PFBS in rats, monkeys, and humans, thereby providing critical information for human health risk assessment. Studies included: (1) intravenous (i.v.) elimination studies in rats and monkeys; (2) oral uptake and elimination studies in rats; and (3) human serum PFBS elimination in a group of workers with occupational exposure to potassium PFBS (K +PFBS). PFBS concentrations were determined in serum (all species), liver (rats), urine (all species), and feces (rats). In rats, the mean terminal serum PFBS elimination half-lives, after i.v. administration of 30 mg/kg PFBS, were: males 4.51 ± 2.22 h (standard error) and females 3.96 ± 0.21 h. In monkeys, the mean terminal serum PFBS elimination half-lives, after i.v. administration of 10 mg/kg PFBS, were: males 95.2 ± 27.1 h and females 83.2 ± 41.9 h. Although terminal serum half-lives in male and female rats were similar, without statistical significance, clearance (CL) was significantly greater in female rats (469 ± 40 mL/h) than male rats (119 ± 34 mL/h) with the area under the curve (AUC) significantly larger in male rats (294 ± 77 μg·h/mL) than female rats (65 ± 5 μg·h/mL). These differences were not observed in male and female monkeys. Volume of distribution estimates suggested distribution was primarily extracellular in both rats and monkeys, regardless of sex, and urine appeared to be a major route of elimination. Among 6 human subjects (5 male, 1 female) followed up to 180 days, the geometric mean serum elimination half-life for PFBS was 25.8 days (95% confidence interval 16.6–40.2). Urine was observed to be a pathway of elimination in the human. Although species-specific differences exist, these findings demonstrate that PFBS is eliminated at a greater rate from human serum than the higher chain homologs of perfluorooctanesulfonate (PFOS) and perfluorohexanesulfonate (PFHxS). Thus, compared to PFOS and PFHxS, PFBS has a much lower potential for accumulation in human serum after repeated occupational, non-occupational (e.g., consumer), or environmental exposures.

Toxicological evaluation of potassium perfluorobutanesulfonate in a 90-day oral gavage study with Sprague–Dawley rats

Perfluorobutanesulfonate (PFBS) is a surfactant and degradation product of substances synthesized using perfluorobutanesulfonyl fluoride. A 90-day rat oral gavage study has been conducted with potassium PFBS (K +PFBS). Rats were dosed with K +PFBS at doses of 60, 200, and 600 mg/kg-day body weight. The following endpoints were evaluated: clinical observations, food consumption, body weight, gross and microscopic pathology, clinical chemistry, and hematology. In addition, functional observation battery and motor activity assessments were made. Histological examination included tissues in control and 600 mg/kg-day groups. Additional histological examinations were performed on nasal cavities and turbinates, stomachs, and kidneys in the 60 and 200 mg/kg-day groups. No treatment-related mortality, body weight, or neurological effects were noted. Chromorhinorrhea (perioral) and urine-stained abdominal fur were observed in males at 600 mg/kg-day. Red blood cell counts, hemoglobin, and hematocrit values were reduced in males receiving 200 and 600 mg/kg-day; however, there were no adverse histopathological findings in bone marrow. Total protein and albumin were lower in females at 600 mg/kg-day. There were no significant changes in clinical chemistry in either sex. All rats appeared normal at sacrifice. Microscopic changes were observed only at the highest dose in the stomach. These changes consisted of hyperplasia with some necrosis of the mucosa with some squamous metaplasia. These effects likely were due to a cumulative direct irritation effect resulting from oral dosing with K +PFBS. Histopathological changes were also observed in the kidneys. The changes observed were minimal-to-mild hyperplasia of the epithelial cells of the medullary and papillary tubules and the ducts in the inner medullary region. There were no corresponding changes in kidney weights. Clinical chemistry parameters related to kidney function were unchanged. These kidney findings are likely due to a response to high concentration of K +PFBS in tubules and ducts and represent a minimal-to-mild effect. Microscopic changes of an equivocal and uncertain nature were observed in the nasal mucosa and were likely attributable to the route of dosing (oral gavage). The NOAEL for the female rat in this study was 600 mg/kg-day (highest dose of study). The NOAEL for the male rat was 60 mg/kg-day based on hematological effects.

Acute and Chronic Effects of Perfluorobutane Sulfonate (PFBS) on the Mallard and Northern Bobwhite Quail

Perfluorobutane sulfonate (PFBS) can be a final degradation product of perfluorobutane sulfonyl fluoride (PBSF)-based chemicals. Surfactants based on this chemistry are potential replacements for perfluorooctane sulfonate (PFOS)-related products and have many potential applications in industrial and commercial processes and applications. To evaluate the potential hazard that PFBS may pose to avian species, acute dietary studies with juvenile mallards and northern bobwhite quail, as well as a quail dietary chronic study of reproduction were conducted. In the acute studies, 10-day-old mallards and quail were exposed to nominal dietary concentrations of 1,000, 1,780, 3,160, 5,620 or 10,000 mg PFBS/kg feed, wet weight (ww) for 5 days and the birds were then fed an untreated diet and observed for up to 17 days. No treatment-related mortalities were observed in the study up to 10,000 mg PFBS/kg, ww feed. Body weight gains of quail exposed to 5620 or 10,000 mg PFBS/kg feed were statistically less than that of unexposed controls. Weight gain of mallards exposed to 10,000 mg PFBS/kg feed was statistically less than that of controls. There were no statistically significant effects on feed consumption of either species. In the acute studies, no observed adverse effect concentration (NOAEC) for mallards and quail were 5620 and 3160 mg PFBS/kg, ww feed, respectively. In a reproduction study, adult quail were exposed to nominal dietary concentrations of 100, 300, or 900 mg PFBS/kg, ww feed for up to 21 weeks. There were no treatment-related mortalities or effects on body weight, weight gain, feed consumption, histopathology measures, or reproductive parameters evaluated in the study when compared to the control group. Concentrations of PFBS in blood serum, liver, and eggs were dose-dependent but were less than the administered dose, indicating biodiminution. Based on the results from the quail reproduction study, the dietary NOAEC was 900 mg PFBS/kg, ww feed (equivalent to an ADI of 87.8 mg PFBS/kg bw/d).

Perfluorobutanesulfonyl fluoride — 1,8-diazabicyclo[5.4.0]undec-7-ene as a useful system in diol-epoxide transformation

The combination of n-perfluorobutanesulfonyl fluoride with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) proves to be a highly efficient system for the conversion of vicinal diols into epoxides, especially well-suited in demanding situations.

The Reaction of Perfluorobutanesulfonyl Fluoride with Alcohols in the Presence of 4‐Dialkylaminopyridines

AbstractPrimary hydroxy groups as in neopentyl alcohol 7 or neopentylglycol 18 react readily with perfluorobutanesulfonyl fluoride 1 in the presence of 2 equiv. of the nucleophilic 4‐dialkylaminopyridines 4 to afford high yields of the corresponding N‐alkyl‐4‐dialkylaminopyridinium perfluorobutanesulfonates (nonaflates). Secondary hydroxy groups give rise to a mixture of the corresponding olefins and monofluorides as well as of the corresponding N‐alkyl‐4‐dialkylaminopyridinium nonaflates.

Novel synthesis of unusual classes of fluorocarbon organosulfur compounds using elemental fluorine as a reagent

The reactions of elemental fluorine with branched alkyl mercaptans, alkanesulfonyl fluorides, alkyl thioethers, cyclic alkyl thioethers, alkyl sulfones, and an alkanesultone have been studied. The synthesis and characterizations of perfluoroisobutylsulfur pentafluoride, perfluoroneopentylsulfur pentafluoride, perfluoropropylsulfur pentafluoride, perfluorotetramethylenesulfur tetrafluoride, perfluoro-1,4-thioxane tetrafluoride, perfluoro-2-propanesulfonyl fluoride, 1,1,1,3,3,3-hexafluoro-2-propanesulfonyl fluoride, perfluorotetramethylene sulfone, perfluorobutanesulfonyl fluoride, perfluoro-1,4-butanesultone, and perfluoropropanesulfonyl fluoride are discussed. The 19 F and 13 C{ 19 F} NMR assignments of the fluorinated products are also reported

Thermolyse des halogenures de perfluoroalcanesulfonyle

Perfluoroalkanesulfonyl chlorides [R FSO 2Cl ; R F  CF 3, C 2F 3, C 4F 9], decompose thermally to give the corresponding perfluoroalkyl chlorides with evolution of SO 2. The latter retards the reaction, but it is catalysed by copper which also inhibits the SO 2 effect. 2-methyl-2-nitrosopropane traps the perfluoroalkyl free radicals. In the presence of a perfluoroalkyl iodide [R′ FI ≠ R′ F≠R F], other products, R FI and R FCl, are obtained. A free radical chain-mechanism is then suggested. On the other hand, perfluorobutanesulfonyl fluoride is very stable thermally.

Darstellung und eigenschaften von octafluorbutansulfonsäure H(CF 2) 4SO 3H und einigen ihrer derivate

Perfluorobutanesulfonyl fluoride C 4F 9SO 2F, obtained by electrofluorination of sulfolene, may contain up to 10 % of perfluorotetramethylene sulfone. Upon hydrolysis with base, this sulfone yields octafluorobutanesulfonate ion H(CF 2) 4SO ø 3 (V). Perfluorobutanesulfonic acid and octafluorobutanesulfonic acid (VI) which are readily obtained from the salts and H 2SO 4 can be separated via fractional distillation. VI forms a crystalline monohydrate, M.P. 45°C. The trimethylsilyl ester was obtained from VI and (CH 3) 3 SiCl. Upon heating above 250° the K sulfonate (Vb) liberates HF.