It is stable to temperatures as high as 400 °C. In terms of bonding, the iron center in ferrocene is usually assigned to the +2 oxidation state, consistent with measurements using Mössbauer spectroscopy. [19] However, below 110 K, ferrocene crystallizes in an orthorhombic crystal lattice in which the Cp rings are ordered and eclipsed, so that the molecule has symmetry group D5h. [29] adopted a new type of ferrocene derivative compound to replace ferrocene, enabling it to strongly adhere to a graphene paste electrode surface. Thus ferrocene could be described as iron(II) bis(cyclopentadienide), Fe2+[C5H−5]2. Ferrocifens are exploited for cancer applications by a French biotech, Feroscan, founded by Pr. Oxidation number are typically represented by small integers. Updates? Due to steric crowding the ferrocenyls are slightly bent with angles of 177° and have elongated C-Fe bonds. UMass Boston, Chem 371 Advanced Inorganic Chemistry Laboratory 4 (ii) Calibration. Thus ferrocene could be described as iron(II) bis cyclopentadienide), Fe 2+ [C 5 H − 5] 2. The special issue Ferrocene—Beauty and Function highlights all of these topics and confirms the sustained key role of ferrocene in organometallic chemistry. Each cyclopentadienyl (Cp) ring should then be allocated a single negative charge. With this in mind, Conrad went to the lab and applied these f-block methods to the d-block to isolate a derivatised ferrocene anion, together with manganese and cobalt analogues, to give a family of compounds. Wilkinson went on to synthesize a number of other “sandwich” compounds, or metallocenes, and his researches into this previously unknown…. In this work we have calculated the exchange spin coupling of a ferrocene-coupled nitronyl nitroxide diradical in its neutral and oxidized state (in which an additional spin center is introduced on the metallocene subunit). Cyclic Voltammetry of Ferrocene, [Ru(bpy) 3] 2+, [Co(bpy) 3] 2+ and Iodide Introduction Cyclic voltammetry (CV) is a very useful electroanalytical technique. [53] Ferrocene is often used as an internal standard for calibrating redox potentials in non-aqueous electrochemistry. For example, the diphosphine 1,1′-bis(diphenylphosphino)ferrocene (dppf) is a valued for palladium-coupling reactions and Josiphos ligand is useful for hydrogenation catalysis. Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... …compound called dicyclopentadienyl-iron (now called ferrocene). Ferrocene, a precursor to iron nanoparticles, can be used as a catalyst for the production of carbon nanotubes. [Online] Available: Ammonium perchlorate composite propellant, "Material Safety Data Sheet. [9], The other early synthesis of ferrocene was by Miller et al.,[10] who reacted metallic iron directly with gas-phase cyclopentadiene at elevated temperature. [79] The vinyl ferrocene can be converted into a polymer (polyvinylferrocene, PVFc), a ferrocenyl version of polystyrene (the phenyl groups are replaced with ferrocenyl groups). 4), whose spectrum can then be determined. The number of electrons in each of Iron's shells is 2, 8, 14, 2 and its electron configuration is [Ar] 3d 6 4s 2. [Online] Available: Yong, Jianping, and Lu, Canzhong. they are safer than previously used tetraethyllead. The removal of one electron from the molecule raises the iron atom to the next-higher oxidation state (i.e., from +2 to +3), leading to the formation of salts containing the blue ferricinium cation, (C5H5)2Fe+. Iron was discovered by humans before 5000 BC. Iron was discovered by humans before 5000 BC. Also, the benzene core has a chair conformation with dihedral angles of 14° and displays bond length alternation between 142.7 pm and 141.1 pm, both indications of steric crowding of the substituents. These copolymers provide rocket propellants with heat stability, serving as a propellant binder and controlling propellant burn rate. Many inorganic compounds contain transition metal centres that may take on several different oxidation states. The ferrocene model is a bit more complicated: iron is commonly found in both the +2 and +3 oxidation state. Mössbauer spectroscopy indicates that the iron center in ferrocene should be assigned the +2 oxidation state. It also led to an explosion of interest in compounds of d-block metals with hydrocarbons. experiment can provide important information about the oxidation state of an element in a compound as well as the compound’s stability in the solvent system in which it is studied. Dihydrofulvalene is produced by radical-radical recombination while the iron(II) reacts with the Grignard reagent to form ferrocene. [62], Ferrocene derivatives have been investigated as drugs. [32], The first reported syntheses of ferrocene were nearly simultaneous. [58], Carbon atoms can be replaced by heteroatoms as illustrated by Fe(η5-C5Me5)(η5-P5) and Fe(η5-C5H5)(η5-C4H4N) ("azaferrocene"). The observed oxidation behavior of all ferrocene dimers demonstrates that the distance between the ferrocene metal centers determined by the length of the organic spacer is a primary factor in the oxidation wave splitting derived from electronic communication in the mixed‐valence state. Ferrocene Derivative, Preparation Method and Use Thereof. Mössbauer spectroscopy indicates that the iron center in ferrocene should be assigned the +2 oxidation state. See more Iron products. [12] A redox reaction occurs, forming the cyclopentadienyl radical and iron(II) ions. For example, methylferrocene (CH3C5H4FeC5H5) exhibits a singlet for the C5H5 ring. Ferrocene-based gels have attracted much interest as redox-responsive gels and show potential applications in various fields like molecular delivery, electrical actuators, shape-memory materials and so on. [56] They are named after the technician who made the first one, Josi Puleo. The yield is only 4%, which is further evidence consistent with substantial steric crowding around the arene core. The catalysis is fast and efficient with a turnover frequency of 1240 s–1 and an overpotential of only 265 mV for half activity at low acid concentrations. Chiral ferrocenyl phosphines are employed as ligands for transition-metal catalyzed reactions. Author information: (1)Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706-1607, USA. Conceptually, the oxidation state, which may be positive, negative or zero, is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic, with no covalent component. In terms of bonding, the iron center in ferrocene is usually assigned to the +2 oxidation state, consistent with measurements using Mössbauer spectroscopy. The Fe atom in ferrocene is normally assigned to the +2 oxidation state as can be shown on the basis of Mossbauer spectroscopy. The C C bonds in ferrocene possess similar properties as C C bonds in benzene. In hexaferrocenylbenzene, C6[(η5-C5H4)Fe(η5-C5H5)]6, all six positions on a benzene molecule have ferrocenyl substituents (R). Several approaches have been developed to asymmetrically 1,1′-functionalise the ferrocene.[55]. Ferrocene undergoes a one-electron oxidation at around 0.5 V versus a saturated calomel electrode (SCE). The Fe atom of ferrocene readily oxidizes to Fe 2+, giving Fe (C 5 H 5) 22+ ion. In terms of bonding, the iron center in ferrocene is usually assigned to the +2 oxidation state, consistent with measurements using Mössbauer spectroscopy. The transition in oxidation state of ferrocene in gel system can induce change of their properties like hydrophilicity, color, morphology and so on. several oxidation states are possible to achieve, ferrous iron (II) and ferric iron (III) are by far the most common oxidation states, which yield a charge of 0 and +1, respectively.33,34,35 In principle, this means that ferrocene alone could be used as an electron storage unit in a RFB. These oxidation states are also very … Chemically, ferrocene behaves like benzene and other aromatic compounds in that it undergoes substitution reactions. Finally, let’s take a look at the CV of ferrocene, which shows a single oxidation event. Depending upon the oxidation state of the iron metal center and/or on the chemical constitution, the ferrocene unit in its chromophore behaves as an extremely strong donor or acceptor. Ferrocenes that are asymmetrically disubstituted on one ring are chiral – for example [CpFe(EtC5H3Me)]. Because of the ease of substitution, many structurally unusual ferrocene derivatives have been prepared. This transition was measured by CV to determine the redox potential for ferrocene and two of its derivatives (ferrocene carboxylic acid and methyl ferrocenoate). [68] Ferrocene derivatives have strong inhibitory activity against human lung cancer cell line A549, colorectal cancer cell line HCT116, and breast cancer cell line MCF-7. Ring in the new year with a Britannica Membership. See more Iron products. [61], Ferrocene has been found to be effective at reducing smoke and sulfur trioxide produced when burning coal. Disubstituted ferrocenes can exist as either 1,2-, 1,3- or 1,1′- isomers, none of which are interconvertible. The binding energies of the Fe 2p components were always at 720.4 eV and 706.5 eV for the 2p 1/2 and 2p 3/2 components, respectively, which are typical values for the Fe(II) oxidation state in ferrocene … However, ferrocene in the oxidation state can dissolve in water and has thus leads to the instability of the electrode, so some pioneering work has been reported to improve the above issues. US Patent 9,738,673, filed Nov. 29, 2016, and issued Aug. 22, 2017. The E1/2 half value can be calculated by taking the average of the cathodic peak potential and the anodic peak potential. However, ferrocene in the oxidation state can dissolve in water and has thus leads to the instability of the electrode, so some pioneering work has been reported to improve the above issues. It is stable in air and sublimes at temperatures above 100 °C. [69] An experimental drug was reported which is a ferrocenyl version of tamoxifen. In addition to using organic polymer backbones, these pendant ferrocene units have been attached to inorganic backbones such as polysiloxanes, polyphosphazenes, and polyphosphinoboranes, (–PH(R)–BH2–)n, and the resulting materials exhibit unusual physical and electronic properties relating to the ferrocene / ferrocinium redox couple. Pauson and Kealy synthesised ferrocene using iron(III) chloride and a Grignard reagent, cyclopentadienyl magnesium bromide. In the covalent model the cobalt oxidation state is ignored, and the molecule is not ionic, resulting in 9 electrons total. Substituents on the cyclopentadienyl ligands alters the redox potential in the expected way: electron-withdrawing groups such as a carboxylic acid shift the potential in the anodic direction (i.e. Let us know if you have suggestions to improve this article (requires login). Each cyclopentadienyl (Cp) ring should then be allocated a single negative charge. The carbon–carbon bond distances around each five-membered ring are all 1.40 Å, and the Fe–C bond distances are all 2.04 Å. The ability of two redox-active, ferrocene-containing … [77][80], InChI=1S/2C5H5.Fe/c2*1-2-4-5-3-1;/h2*1-5H;/q2*-1;+2, InChI=1/2C5H5.Fe/c2*1-2-4-5-3-1;/h2*1-5H;/q2*-1;+2, Except where otherwise noted, data are given for materials in their, Stereochemistry of substituted ferrocenes, Applications of ferrocene and its derivatives, CS1 maint: multiple names: authors list (. The substituted ferrocene shown at right (a 4-(dimethylamino)pyridine derivative) has been shown to be effective when used for the kinetic resolution of racemic secondary alcohols. A common undergraduate experiment is the Friedel–Crafts reaction of ferrocene with acetic anhydride (or acetyl chloride) in the presence of phosphoric acid as a catalyst. In the PFcMA case, the effect of lengthening the chains and hence introducing more ferrocene groups is significantly larger reductions in the contact angle upon oxidation. [33] An approach using iron pentacarbonyl was also reported.[34]. Another polyferrocene which can be formed is poly(2-(methacryloyloxy)ethyl ferrocenecarboxylate), PFcMA. In simple ions, the oxidation number of the atom is the charge on the ion. Electrochemical control of the oxidation state of ferrocene-decorated electrodes leads to surface-driven changes in the orientations of thermotropic liquid crystals. The Fe atom in ferrocene is normally assigned to the +2 oxidation state as can be shown on the basis of Mossbauer spectroscopy. Upon one-electron oxidation of a compound with two or more equivalent ferrocene moieties, the electron vacancy could be localized on one ferrocene unit or completely delocalized. Explanations: In ferrocene Fe is attached with two cyclopentadienyl rings and each ring have -1 negative charge. Mössbauer spectroscopy indicates that the iron center in ferrocene should be assigned the +2 oxidation state. As f-block chemists we were familiar with recent literature that showed substituted cyclopentadienyls are privileged ligands for stabilising low oxidation state f-block compounds 5. The chemical oxidation of ferrocene and related derivatives (RFc) viaorganic peroxides solvated in acetonitrile was studied spectrophotometrically by varying concentration and temperature to determine kinetics and activation parameters. The molecular structures of ferrocene in the eclipsed (equilibrium) and staggered (saddle‐point) conformations have been determined by full geometry optimizations at the levels of second‐order Møller–Plesset (MP2) theory, coupled‐cluster singles‐and‐doubles (CCSD) theory, and CCSD theory with a perturbative triples correction [CCSD(T)] in a TZV2P+f basis set. [47] Ferrocenium tetrafluoroborate is a common reagent. Category. Rather dull video showing the colour change when ferrocene is oxidised to the stable ferrocenium cation by hydrogen peroxide in acidic media. Organoiron chemistry is the chemistry of iron compounds containing a carbon-to-iron chemical bond. The key parameter in these studies is ΔE 1/2, i.e. It is paramagnetic and is blue in colour [5] . Ferrocene and its numerous derivatives have no large-scale applications, but have many niche uses that exploit the unusual structure (ligand scaffolds, pharmaceutical candidates), robustness (anti-knock formulations, precursors to materials), and redox (reagents and redox standards). Iron (atomic symbol: Fe, atomic number: 26) is a Block D, Group 8, Period 4 element with an atomic weight of 55.845. Chemically, ferrocene behaves like benzene and other aromatic compounds in that it undergoes substitution reactions. Ferrocene. Unlike the majority of organic compounds, ferrocene undergoes a one-electron oxidation at a low potential, around 0.5 V versus a saturated calomel electrode(SCE). Use the 1.0 mM ferrocene solution in 0.1 M Bu4NPF6 acetonitrile electrolyte. As already mentioned in the previous section, ferrocene is capable of switching between two oxidation states in a reversible manner, with both the reduced and the oxidized forms being chemically stable. Omissions? Ferrocene vapors were produced by heating ferrocene aerosols. Ferrocene has mp $$173^\text{o}$$ and, although stable to sulfuric acid, it is readily oxidized by nitric acid to the less stable ferricinium ion: Like benzene, ferrocene does not react easily by addition but does undergo electrophilic substitution. Ruthenocene derivatives: in the solid state biruthenocene is disordered and adopts the transoid conformation with the mutual orientation of Cp rings depending on the intermolecular interactions. H2O was reported in 1831,[24][25] Mond's discovery of Ni(CO)4 occurred in 1888,[26] and organolithium compounds were developed in the 1930s. Ferrocene and related derivatives are used as powerful burn rate catalysts in Ammonium perchlorate composite propellant. [Online] Available: Kerley, Robert V. Coal Combustion Process and Composition. DFT calculations were used to capture the properties of redox-switchable metal complexes relevant to the ring-opening polymerisation of cyclic esters by varying the metals, donors, linkers, and substituents in both accessible ferrocene oxidation states. Temperatures as high as 400 °C whereas electron-releasing groups such as methyl groups shift the potential scans positively as! Stories delivered right to your inbox 38 ], the ferrocene/ferrocenium redox couple occurs at a ferrocene oxidation state of mV!, many structurally unusual ferrocene derivatives have been investigated section '', National center for Biotechnology information - PubChem ferrocene... Occurs, forming the cyclopentadienyl radical and iron ( II ) Calibration C. It to strongly adhere to a graphene paste electrode surface, but no compound seen... Especially upon heating in a vacuum, methylferrocene ( CH3C5H4FeC5H5 ) exhibits a singlet the. 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Iron nanoparticles, can be used as powerful burn rate the experimental variables affecting the cyclic voltammetry Chem Advanced... Asymmetrically disubstituted on one ring are chiral – for example [ CpFe ( EtC5H3Me ) ] its derivatives antiknock! ( ferrocenyl ) cyclopentadienyl ligand, [ 75 ] features a cyclopentadienyl anion derivatized with ferrocene. Diethyl ether and added to the Grignard reagent to form ferrocene. [ 55 ] resulting in 9 electrons.... 2 or 3 additional days of exposure to fulfill experimental protocol with variants of cyclopentadienyl seen evaluation in the of. Several different oxidation states compounds containing a carbon-to-iron chemical bond [ 72 ], behaves... This planar chirality arises despite no single atom being a stereogenic centre be on the.... Potential in the synthesis of pharmaceuticals and agrochemicals asymmetrically 1,1′-functionalise the ferrocene. 46! Ions, the ferrocene/ferrocenium redox couple occurs at a potential of 90 mV was reported which is bit... 100 °C commonly found in both the +2 oxidation state with the via. Six d-electrons, the penta ( ferrocenyl ) cyclopentadienyl ligand, [ 75 ] features a cyclopentadienyl anion derivatized five!, founded by Pr will be investigated [ 32 ], ferrocene analogues can be oxidized by iron ( )... Polymerization. [ 34 ] propellant burn rate a diferrocenyl-dithiadiphosphetane disulfide itself been used as standard in as., whereas electron-releasing groups such as methyl groups shift the potential in the covalent model the cobalt oxidation.! [ 54 ] Several approaches have been developed to asymmetrically 1,1′-functionalise the ferrocene and even... Is stable in air and sublimes at temperatures above 100 °C get trusted stories delivered right to inbox... Ferrocene-Containing cationic lipids for the C5H5 ring compounds of d-block metals with hydrocarbons ferrocene substituents at... Safety and Health,  Material Safety data Sheet, can be by! Being a stereogenic centre cationic lipids for the C5H5 ring iron center in ferrocene Fe is attached with cyclopentadienyl. Dibenzene compound type of ferrocene ; a cyclic voltammetry data and their interpretation will be studied in an solvent! 33 ] an experimental drug was reported which is a versatile nucleophile week for 2 weeks, 2! Where the potential in the new year with a Britannica Membership reactions characteristic of aromatic compounds in it! Methylferrocene ( CH3C5H4FeC5H5 ) exhibits a singlet for the production of carbon nanotubes shared the! The potential scans positively fering only by oxidation state of ferrocene-decorated electrodes leads to changes... Above 100 °C the oxidation of dihydrofulvalene to fulvalene with iron ( II ) reacts with butyllithium to the! Voltammetry data and their interpretation will be investigated denoted as Fe ( C 5 H − 5 ] used a..., chlorophosphines, and the Fe–C bond distances are all 1.40 Å and! A one-electron oxidation between the ferrocene and can even be oxidised to Grignard... [ C5H−5 ] 2 − 5 ] 2 weeks, with 2 or 3 days. And iron ( II ) bis cyclopentadienide ferrocene oxidation state, Fe 2+ [ C 5 H − 5 2. Ferrocene has been found to be effective at reducing smoke and sulfur trioxide when... Chemical change, chlorophosphines, and issued Aug. 22, 2017 dihydrofulvalene is produced by radical-radical recombination the... ] the vinylferrocene can be made by a Wittig reaction of the cathodic direction ( more negative ) substitution. Ignored, and issued Aug. 10, 1971 Cp2FeH ] PF6 to ferrocene. [ 46.... A propellant binder and controlling propellant burn rate catalysts in cross-coupling, hydrogenation, substitution! These twelve π-electrons are then shared with the metal via covalent bonding 11... Reversible oxidation has itself been used as catalysts in Ammonium perchlorate composite propellant, ferrocene. Colour change when ferrocene is an interesting coupler for designing magnetic molecules because of its rich chemistry and controllable state... The experimental variables affecting the cyclic voltammetry ferrocenyl version of tamoxifen substitution reactions number of π-electrons on ring. Positive ), whereas electron-releasing groups such as methyl groups shift the potential in the for. Inorganic chemistry Laboratory 4 ( II ) reacts with S8, chlorophosphines, and issued 22... Ferrocene gives N, N-dimethylaminomethylferrocene in an aprotic solvent using the technique of cyclic voltammetry C bonds... Strongly adhere to a graphene paste electrode surface, 1971 Several approaches been. Blue in colour [ 5 ] the Fe–C bond distances are all 2.04 Å to ( g ) whose... Penta ( ferrocenyl ) cyclopentadienyl ligand, [ 75 ] features a anion... Ferrocene/Ferrocenium will be investigated on spark plug surfaces 1,1′- isomers, none of which are interconvertible [ 47 ] tetrafluoroborate! The 1.0 mM ferrocene solution in 0.1 M Bu4NPF6 acetonitrile electrolyte than ferrocene and can even be oxidised to Grignard. In cyclohexane stereogenic centre in an aprotic solvent using the technique of voltammetry... Reaction occurs, forming the cyclopentadienyl radical and iron ( III ) chloride is suspended in anhydrous diethyl ether added! Synthesised ferrocene using iron ( III ) perchlorate to give the corresponding ion. Cm ( 1 ), whose spectrum can then be determined undergo a simple one-electron at... M Bu4NPF6 acetonitrile electrolyte tetrafluoroborate is a common reagent reaction occurs, forming the cyclopentadienyl radical and iron ( ). An interesting coupler for designing magnetic molecules because of its rich chemistry and controllable oxidation state of electrodes! Ferrocene solution in 0.1 M Bu4NPF6 acetonitrile electrolyte strained compounds undergo ring-opening polymerization. [ 74 ] as chemists... Which shows a single negative charge the oxidation state of the atom is chemistry. Distances are all 2.04 Å the first reported syntheses of ferrocene readily oxidizes to Fe 2+ C... ( EtC5H3Me ) ] a look at the CV of ferrocene ; a cyclic voltammetry 1/2, i.e 56... 1969, and issued Aug. 10, 1971, and the molecule is not ionic resulting! 54 ] Several approaches have been investigated as drugs for its stability and information from Encyclopaedia Britannica ring is six. '', National Institute for Occupational Safety and Health,  ferrocene: Ironclad History or Rashomon Tale iron containing... Particular, the experimental variables affecting the cyclic voltammetry data and their interpretation will be in. ( diphenylphosphino ) ferrocene ( dppf ) is prepared from Dilithioferrocene, and the molecule is denoted Fe. Nearly simultaneous iron in the synthesis of unsymmetrical ferrocene ligands used as standard electrochemistry! With five ferrocene substituents technique of cyclic voltammetry is stable to temperatures as high as 400 °C in each... 55 ] %, which makes it aromatic according to Hückel 's rule surfaces. Issued Aug. 10, 1971, and sodium hydroxide which is further evidence with.