Fluorosulfonic Acid Research Articles

Electrochemical oxidation of organic compounds in fluorosulfuric acid: Part VII. Comparison of voltammetric oxidation potentials in HSO 3F and acetonitrile

The anodic voltammograms of 32 aromatic compounds with different functional groups were measured both in 0.1 M CH 3COOH/HSO 3F at −76°C vs. a Hg/Hg 2SO 4 electrode in this electrolyte and in 0.1 M tetraethylammonium perchlorate/acetonitrile at room temperature vs. the saturated aqueous calomel electrode. Because of a minimal specific solvent effect in HSO 3F the oxidation of the acridizinium ion 1 and of the N-methylacridium ion 2 to their dication radicals are chosen as reference redox systems for a comparison between both solvents. Specific interactions with HSO 3F, e.g. protonation of functional groups, formation of arenium ions, acylium ions or benzyl cations as well as a fluorosulfonation, are indicated by a characteristic positive shift of the anodic half-peak potential with respect to the acetonitrile scale.

Aromatic fluoroderivatives. XCV. The investigation of the behaviour of the polyfluoroaromatic compounds containing group VA elements in acid media

The formation of the stable phosphonium ions from polyfluoroaromatic phosphines of C 6F 5PX 2 type [X = H, CH 3, C 6H 5, C 6F 5, Cl, F, NCS, CN, OCH 3, N(C 2H 5) 2] in HSO 3FSbF 5 (1:1) at −70 to −1O°C has been shown, as well as the transformation of the investigated phosphines in HSO 3F at 20°C into the pentavalent phosphorus derivatives.The same processes take place also for the trivalent arsenic and antimony derivatives. The possible routes of the latter reaction together with the determining factors have been discussed. The unusual formation of the protonated form of difluoroanhydride of pentafluorobenzenephosphonic acid from C 6F 5P(OCH 3) 2 and C 6F 5P(CN) 2 in HSO 3F has been found. The generation of nitrenium cations from the polyfluorinated nitrosobenzenes in the strong acids at −60°C has been proved. At 20°C in the same media these cations undergo oxidation leading to the corresponding nitrobenzenes. The influence of the acidity of media on the reactions of nitrosobenzenes has been investigated.

Electrochemical oxidation of organic compounds in fluorosulfuric acid—III. Voltammetric investigation of aromatic carboxylic acids and acylium ions

The anodic behavior of a series of substituted benzoic acids 1a – 1w and of the corresponding benzoylium ions 5 is investigated by cyclic voltammetry in fluorosulfuric acid at −76°C. The acids are oxidized to cation radicals, the stability of which decreases with decreasing number of alkyl substituents. As a subsequent reaction the functionalization of one of the methyl groups to the fluorosulfonyloxymethyl group is found. After dissolving at room temperature of the acids with one o-alkyl group are between 80 and 100% and the acids with two o-alkyl groups are completely transformed into benzoylium ions 5 , which are between 450 and 560 mV more positively oxidized than the acid. The main reaction of the dication radical formed is the addition of SO 3F − to the carbonylium C-atom. As the number of alkyl substituents decreases this reaction competes with the functionalization of a methyl group. The difference between the voltammetric data in HSO 3F and acetonitrile is discussed in terms of a protonation of the benzoic acids and their oxidation products.

Elektrochemische Oxydation organischer Verbindungen in Fluorsulfonsäure. IV. Voltammetrische Untersuchungen zur Bildung und zum anodischen Verhalten einiger Benzylkationen und Arenium‐Ionen

Electrochemical Oxidation of Organic Compounds in Fluorosulfuric Acid. IV. Voltammetric Investigation of the Formation and of the Anodic Behaviour of Some Benzyl Cations and Arenium IonsThe anodic behavior of a series of benzylic alcohols, ethers or acetates 1–10, benzyl cyanides 11–21 and aromatic hydrocarbons 22–35 is investigated by cyclic voltammetry in fluorosulfuric acid at −76°C. The oxidation of the benzyl cations ArCH+2 formed from a part of the benzylic compounds leads at potentials by 0,7 to 0.8 V more positive than those of the neutral compounds with addition of SO3F− to stable cation radicals ArCH2OSO2F+. In a further oxidation step another CH3‐group is functionalized to CH2OSO2F. The anodic peak potentials of the arenium ions are by about 1.1 V more positive than those of the nonprotonated hydrocarbons. The dissociation equilibrium of ArCH2OSO2F und the protonation equilibrium of the hydrocarbons are discussed in terms of the donor ability of the aromatic compounds at borderline cases.

Elektrochemische Oxydation organischer Verbindungen in Fluorsulfonsäure. I. Voltammetrische Untersuchung von Arylsulfonylfluoriden

Electrochemical Oxidation of Organic Compounds in Fluorosulfuric Acid. I. Voltammetric Investigation of ArylsulfofluoridesThe electrochemical oxidation of phenylsulfonylfluoride 1g and 16 of its alkylsubstituted derivates 1a–1g as well as a series of monomeric and dimeric products of the chemical oxidation of 1 were investigated by cyclic voltammetry in fluorosulfuric acid at –76°C. In all cases cation radicals could be detected as primary oxidation products. In further reaction steps one or two meta‐ or ortho‐methyl groups are converted into fluorosulfonyloxymethyl groups. Depending on the stability of the cation radicals this process occurs either through an EEC‐mechanism via the intermediate formation of dications (penta‐ and tetramethylsubstituted compounds) or through an ECE‐mechanism with rate determining deprotonation of the cation radical.

Aluminium tris(flourosulphate)

Aluminium tris(fluorosulphate) is prepared by the reaction of aluminium tris(trifluoroacetate) and fluorosulphuric acid. The IR spectrum indicates a polymeric structure containing bridging bidentate fluorosulphate groups, giving hexacoordination around aluminium. Aluminium tris(fluorosulphate) forms coordination compounds with pyridine and bipyridyl.

Elektrochemische Oxidation organischer Verbindungen in Fluorsulfonsäure. V. Anodisches Verhalten aromatischer Nitroverbindungen, Nitrile, Amine, Acetamide und Oxime

Electrochemical Oxidation of Organic Compounds in Fluorosulfuric Acid. V. Anodic Behaviour of Aromatic Nitrocompounds, Nitriles, Amines, Acetamides, and OximesThe anodic behaviour of a series of methyl substituted nitrobenzenes, benzonitriles, aniline derivatives, acetanilides and acetophenone oximes was investigated by cyclic voltammetry at platinum electrodes in HSO3F at −76°C. With the exception of the parent compounds and partly of the monomethyl derivatives relatively stable cation radicals could be detected. In a second anodic wave in many cases the functionalization of a CH3‐group to CH2‐OSO2F took place. From a comparison of the peak potentials and from the dependence of the voltammetric curves on the scan rate follows that the aniline derivatives are oxidized without deprotonation of the −NH3+ group, whereas for the nitrocompounds, nitriles and acetanilides a deprotonation of the functional group is coupled with the oxidation, and the cation radicals are stable onyl in the deprotonated state. A kinetic study of the subsequent reaction of some nitrocompounds was made and the deviating behavior of some acetanilides was found to be due to the anodic dimerization to benzidine derivatives.

Elektrochemische Oxidation organischer Verbindungen in Fluorsulfonsäure. VI. Voltammetrische Untersuchungen zur Oxidierbarkeit heterocyclischer Kationen

Electrochemical Oxidation of Organic Compounds in Fluorosulfuric Acid. VI. Voltammetric Investigation about the Oxidability of Heterocyclic CationsThe anodic behavior of a series of pyridinium, quinolinium, isoquinolinium, pyrylium, tropylium, pyrazolium and imidazolium cations and of some of their benzoderivatives was investigated by cyclic voltammetry in HSO3F at −76°C. Because of the available very positive potential region under these conditions almost all cations were oxidized, and in many cases relatively stable dication radicals could be detected. The oxidation potential decreases with decreasing acceptor ability of the heterocyclic ring, increasing extension of the π‐electron system and increasing donor effects of substituents. There was no significant difference between the curves obtained from the N‐alkylated and the corresponding N‐protonated heterocyclic compounds, which showed that the oxidation is not coupled with the N‐deprotonation. The voltammograms of phenylsubstituted pyrylium and pyrazolium ions as well as of benzimidazolium ions display typical marks of the anodic aromatic dimerization, which hitherto seemed to have been restricted to donor substituted benzenes and π‐excess heterocycles.

1,3-Oxazines and related compounds. VI. Synthesis and some reactions of 2,6-disubstituted 4H-1,3-thiazin-4-ones.

Various of 2, 6-disubstituted 4H-1, 3-thiazin-4-ones (5) were synthesized by successive treatment of N-acylacetylcarboxamides with acid (such as 70% perchloric acid or fluorosulfonic acid) and hydrogen sulfide. Reactions of 5 were investigated ; ammonolysis with ethanolic ammonia gave the corresponding pyrimidin-4-ones; hydrolysis of 2-alkyl-1, 3-thiazine derivatives yielded ring-opened N-acyl-β-mercaptocrotonamides ; reduction with NaBH4 or LiAlH4 afforded 3, 4-dihydro-2H-1, 3-thiazin-4-one derivatives.

Solid-state multiple-pulse proton NMR studies of doped Poly( p-phenylene)

Recently, it has been found that the conductivity of poly(p-phenylene) (PPP) increases by more than ten orders of magnitude upon doping with certain strong electron donors or acceptors [1]. Few studies of this doping mechanism have been reported [2]. By virtue of its sensitivity to the electronic environment of the nucleus, the solid-state NMR technique has provided important information on similar processes in the doping and conduct ion in polyacetylene [3, 4]. We report studies of the proton resonance in poly(p-phenylene) using multiple-pulse NMR techniques which indicate that these techniques may be useful for probing the environment of such doped conductive polyphenylenes. Many substances have been found to be good dopants for PPP [2], including electron donors such as metal naphthylides and the pure metals and alloys of lithium, sodium, and potassium, and electron acceptors such as arsenic pentafluoride, ant imony pentachloride, fluorosulfonic acid, iodine pentafluoride, and ferric chloride. Our studies include PPP doped with all of these except arsenic pentafluoride, the metal alloys, and lithium. Samples for s tudy by NMR spectroscopy were prepared in NMR tubes and sealed while attached to the vacuum manifold. For liquid dopants, PPP was exposed to the dopant directly. After reaction, excess dopant was removed by evacuation and mild heating, if necessary. Metal dopants were heated to melting to produce the doping reaction. Metal naphthylides were prepared by a standard technique and doping was accomplished as with the liquid dopants, the THF being removed by evacuation. Ferric chloride was dissolved in nitromethane for doping. Typical doping times were in the range of four to seven days. Solid-state proton NMR spectra were obtained using the 8-pulse sequence first demonstrated by Rhim e t al. [5]. The sequence greatly at tenuates dipole-dipole broadening of the resonance line, as shown in Fig. 1 for PPP. As can be seen, the use of the 8-pulse sequence reduces the linewidth by nearly two orders of magnitude. The important point to be made is that the lineshape of the multiple-pulse spectrum does not appear to be dominated by chemical-shift anisotropy. The line is approximately Gaussian

Concerted [4+2] and stepwise [2+2]cycloadditions of the triphenylallenyl cation with cyclopentadiene

The triphenylallenyl cation ( 5 ), generated in situ under different conditions, reacts with cyclopentadiene via allyl cations 7 and 9 . The exclusive formation of 7 from 12 and FSO 3H proves a concerted [4+2]cycloaddition leading to 9 and suggests a stepwise [2+2]cycloaddition reaction to give 7 .

Protonation of syn-Bicyclo[4.2.1]nona-2,4,7-trien-9-ol with Fluorosulfuric Acid. Direct Evidence for Protonation Sites

Abstract Treatment of syn-9-hydroxybicyclo[4.2.1]nona-2,4,7-triene (1) with fluorosulfonic acid in sulfur dioxidedichloromethane-d2 cleanly provided protonated dimeric ether and the 7-hydroxytricyclo[4.2.1.02,8]nona-3-en-5-yl cation. Direct NMR observation as well as quenching experiment of these cations unequivocally established protonation at C-2 (or C-5) and C-7 (or C-8) of 1.

The fluorosulfate ion acceptor ability of selected transition metal fluorosulfates

The acceptor ability of transition metal fluorosulfates towards the SO 3F − ion is restricted almost entirely to binary fluorosulfates with the metal from the 4d or the 5d block. Two general manifestations of acceptor behavior are found: (i) The formation of complexes containing the anion [M(SO 3F) n] m− and (ii) acidic behavior of M(SO 3F) n in fluorosulfuric acid. The availability of a general, convenient synthetic route to complexes with [M(SO 3F) n] m−ions has afforded a large number of examples generally containing the [M(SO 3F) 6] m−ion. However acidic behavior is restricted to very few examples, where M = Au or Pt, for two main reasons: (i) The unavailability of suitable binary fluorosulfate with M in a sufficiently high oxidation state, or (ii) their lack of solubility in HSO 3F. The discussion will center around some unusual complexes and some acidity measurements supported by sample calculations.

Electrolytic preparation of bis(fluorosulfuryl) peroxide

One of the known methods for producing bis (fluorosulfuryl) peroxide is electrolysis under vacuum at about −23°C of a dilute solution of potassium fluorosulfate in fluorosulfuric acid. This process has now been improved by increasing the concentration of the dissolved salt, thereby increasing the electrical conductivity and lowering the vapor pressure of the electrolyte. Both the rate and the current efficiency of production of S 2O 6F 2 have been increased and loss of HSO 3F by evaporation has been reduced. A current efficiency of about 92% has been found for a cell operating at about −8°C with platinum electrodes in an electrolyte containing about three moles of HSO 3F per mole of KSO 3F. Potassium fluorosulfate combines with fluorosulfuric acid to form the compound, KSO 3F. 3HSO 3F, which melts at −10°C. The formation of compounds having compositions KSO 3F. xHSO 3F (x=3−5)are also indicated and will be discussed.

Fluorosulfates of group(IV) elements

Synthesis of binary and ternary fluorosulfates of tin and germanium by metal oxidation in a HSO 3F/S 2O 6F 2 mixture is investigated. Attempts to obtain Ge(SO 3F) 4 resulted in the formation of GeF 2(SO 3F) 2. Instead Ge(SO 3F) 4 has been stabilized by the formation of M 2[Ge(SO 3F) 6] (where M = Cs or Cl0 2) complexes. In the tin system simple alternative routes to the previously known Sn(SO 3F) 4 and M 2[Sn(SO 3F) 6] are found. In addition a new compound of the composition Cs[Sn(SO 3F) 5] is formed and identified by the Mossbauer spectrum as a novel structural type with an oligomeric anion. Structural conclusions are based on vibrational spectra (Raman and 1R). 119Sn Mossbauer spectra and solution studies in HSO 3F via conductivity and NMR ( 19F and 119Sn) measurements. Attempted synthesis of Sn(II)Sn(IV)(SO 3F) 6 was not successful.

Organothallium compounds. XVIII. The effect of antimony pentafluoride and fluorosulfuric acid on the thallation of polyfluoroarenes

The polyfluoroarenes m-H2C6F4, m-O2NC6F4H, m- and p-BrC6F4H, (p-HC6F4)2, C6F5H, 1,3,5-F3C6H3 and m-FSO2C6F4H have been thallated by thallic trifluoroacetate in fluorosulfuric acid in the presence of antimony pentafluoride. Substantial dithallation of m-H2F4 and 1,3,5-F3C6H3 and slight trithallation of the latter have been achieved. The products were identified by conversion into the corresponding polyfluoroiodoarenes on reaction with aqueous sodium iodide. From the reaction with pentafluorobenzene, pentafluorophenylthallium(III) species have been characterized. 1,2,4,5-Tetrafluoro-3-methoxybenzene was thallated by thallic trifluoroacetate in 1,2-dichloroethane in the presence of boron trifluoride etherate, but C6F5H and p-MeC6F4H failed to react.

Fluorosulfates of the noble metals, part 4 fluorosulfates of iridium

The synthesis of the binary fluorosulfates Ir(SO 3F) 3 and Ir(SO 3F) 4 and of the ternary fluorosulfates (ClO 2) 2[Ir(SO 3F) 6], Cs 2[Ir(SO 3F) 6] and Ba[Ir(SO 3F) 6 is described. The preparative runs are characterized by long reaction times, often up to several weeks, even at elevated temperatures, due to the relative inertness of iridium towards the strongly oxidizing reaction mixture of bis(fluorosulfuryl)- peroxide, S 2O 6F 2, and fluorosulfuric acid, HSO 3F. Structural characterizations are based on infrared spectra and in case of the Ir(IV) compounds on temperature dependant magnetic susceptibility measurements. The magnetic moments μ eff obtained are slightly below the calculated values suggesting weak antiferromagnetic coupling.

Neue Methode zur Herstellung von 1‐Acylpyridiniumsalzen

New Preparation of 1‐Acylpyridinium Salts1‐Acyl‐4‐alkylidene‐1,4‐dihydropyridines 1 react with protonic acids like, e. g., tetrafluoroboric or fluorosulfonic acid (2) to give 1‐acyl‐4‐alkylpyridinium salts 3 in nearly quantitative yields.

Reactions of sulfur nitride (S4N4) with antimony pentachloride, antimony pentafluoride, arsenic pentafluoride, phosphorus pentafluoride, and fluorosulfuric acid. Preparation and crystal structures of salts of the S4N42+ cation: (S4N4)(Sb3F14)(SbF6), (S4N4)(SO3F)2, (S4N4)(AsF6)2.cntdot.SO2, (S4N4)(AlCl4)2, and (S4N4)(SbCl6)2

Reactions of sulfur nitride (S4N4) with antimony pentachloride, antimony pentafluoride, arsenic pentafluoride, phosphorus pentafluoride, and fluorosulfuric acid. Preparation and crystal structures of salts of the S4N42+ cation: (S4N4)(Sb3F14)(SbF6), (S4N4)(SO3F)2, (S4N4)(AsF6)2.cntdot.SO2, (S4N4)(AlCl4)2, and (S4N4)(SbCl6)2

The anodic behavior of saturated hydrocarbons in fluorosulfuric acid Part I. Study of the oxidation mechanism

The mechanism of anodic oxidation of saturated hydrocarbons in fluorosulfuric acid has been established with cyclopentane and cyclohexane. Two monoelectronic transfers are separated by a chemical reaction which is a deprotonation: RH→[RH] ⋎+ + e − E [RH] ⋎+ →R ⋎ +H + C R ⋎ →R + + e − E This ECE mechanism is supported by cyclic voltammetry and coulometries performed at cryogenic temperatures. It is shown that R is chemisorbed at low temperature: R radicals are hard and can give a complex with the platinum atoms of the anode which are also hard (because they are strongly deficient in electrons). Such a complex formation can explain why R is more difficult to oxidize than the parent hydrocarbon RH.