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The halogens are a group in the periodic table consisting of six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts), though some authors would exclude tennessine as its chemistry is unknown and is theoretically expected to be more like that of gallium. In the modern IUPAC nomenclature, this group is known as group (XVII) or group (VII).
Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at 114 °C (237 °F), and boils to a violet gas at 184 °C (363 °F). The element was discovered by the French chemist Bernard Courtois in 1811 and was named two years later by Joseph Louis Gay-Lussac, after the Ancient Greek Ιώδης 'violet-coloured'.
Sulfuric acid or sulphuric acid, known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, and hydrogen, with the molecular formula H2SO4. It is a colorless, odorless, and viscous liquid that is miscible with water.
Nitrous acid is a weak and monoprotic acid known only in solution, in the gas phase and in the form of nitrite salts. Nitrous acid is used to make diazonium salts from amines. The resulting diazonium salts are reagents in azo coupling reactions to give azo dyes.
In chemistry, an electrophile is a chemical species that forms bonds with nucleophiles by accepting an electron pair. Because electrophiles accept electrons, they are Lewis acids. Most electrophiles are positively charged, have an atom that carries a partial positive charge, or have an atom that does not have an octet of electrons.
Karl Fischer titration is a classic titration method in chemical analysis that uses coulometric or volumetric titration to determine trace amounts of water in a sample. It was invented in 1935 by the German chemist Karl Fischer. Today, the titration is done with an automated Karl Fischer titrator.
Hydroiodic acid is an aqueous solution of hydrogen iodide (HI). It is a strong acid, i.e. an acid that is ionized completely in an aqueous solution. It is colorless. Concentrated solutions are usually 48% to 57% HI.
Hydrogen bromide is the inorganic compound with the formula HBr. It is a hydrogen halide consisting of hydrogen and bromine. A colorless gas, it dissolves in water, forming hydrobromic acid, which is saturated at 68.85% HBr by weight at room temperature. Aqueous solutions that are 47.6% HBr by mass form a constant-boiling azeotrope mixture that boils at 124.3 °C. Boiling less concentrated solutions releases H2O until the constant-boiling mixture composition is reached.
Sodium thiosulfate is an inorganic compound with the formula Na2S2O3·xH2O, where x indicates the number of water molecules in the compound. Typically it is available as the white or colorless pentahydrate, Na2S2O3·5H2O. The solid is an efflorescent crystalline substance that dissolves well in water.
Hydrogen iodide is a diatomic molecule and hydrogen halide. Aqueous solutions of HI are known as hydroiodic acid or hydriodic acid, a strong acid. Hydrogen iodide and hydroiodic acid are, however, different in that the former is a gas under standard conditions, whereas the other is an aqueous solution of the gas. They are interconvertible. HI is used in organic and inorganic synthesis as one of the primary sources of iodine and as a reducing agent.
The sulfur–iodine cycle is a three-step thermochemical cycle used to produce hydrogen.
The iodine clock reaction is a classical chemical clock demonstration experiment to display chemical kinetics in action; it was discovered by Hans Heinrich Landolt in 1886. The iodine clock reaction exists in several variations, which each involve iodine species and redox reagents in the presence of starch. Two colourless solutions are mixed and at first there is no visible reaction. After a short time delay, the liquid suddenly turns to a shade of dark blue due to the formation of a triiodide–starch complex. In some variations, the solution will repeatedly cycle from colorless to blue and back to colorless, until the reagents are depleted.
The Briggs–Rauscher oscillating reaction is one of a small number of known oscillating chemical reactions. It is especially well suited for demonstration purposes because of its visually striking colour changes: the freshly prepared colourless solution slowly turns an amber colour, then suddenly changes to a very dark blue. This slowly fades to colourless and the process repeats, about ten times in the most popular formulation, before ending as a dark blue liquid smelling strongly of iodine.
Iodine can form compounds using multiple oxidation states. Iodine is quite reactive, but it is much less reactive than the other halogens. For example, while chlorine gas will halogenate carbon monoxide, nitric oxide, and sulfur dioxide, iodine will not do so. Furthermore, iodination of metals tends to result in lower oxidation states than chlorination or bromination; for example, rhenium metal reacts with chlorine to form rhenium hexachloride, but with bromine it forms only rhenium pentabromide and iodine can achieve only rhenium tetraiodide. By the same token, however, since iodine has the lowest ionisation energy among the halogens and is the most easily oxidised of them, it has a more significant cationic chemistry and its higher oxidation states are rather more stable than those of bromine and chlorine, for example in iodine heptafluoride.
In inorganic chemistry, sulfonyl halide groups occur when a sulfonyl functional group is singly bonded to a halogen atom. They have the general formula RSO2X, where X is a halogen. The stability of sulfonyl halides decreases in the order fluorides > chlorides > bromides > iodides, all four types being well known. The sulfonyl chlorides and fluorides are of dominant importance in this series.
Iodine oxides are chemical compounds of oxygen and iodine. Iodine has only two stable oxides which are isolatable in bulk, iodine tetroxide and iodine pentoxide, but a number of other oxides are formed in trace quantities or have been hypothesized to exist. The chemistry of these compounds is complicated with only a few having been well characterized. Many have been detected in the atmosphere and are believed to be particularly important in the marine boundary layer.
An insertion reaction is a chemical reaction where one chemical entity interposes itself into an existing bond of typically a second chemical entity e.g.:
Samarium(III) iodide is an inorganic compound, a salt of samarium and hydroiodic acid with the chemical formula SmI
3.
Europium(III) iodide is an inorganic compound containing europium and iodine with the chemical formula EuI3.
Disulfur diiodide is an unstable inorganic chemical compound with the chemical formula S2I2. Its empirical formula is SI. It is a red-brown solid that decomposes above −30 °C to elemental sulfur and iodine.
References
- ↑ Yanwei Zhang; Pingan Peng; Zhi Ying; Qiaoqiao Zhu; Junhu Zhou; Zhihua Wang; Jianzhong Liu; Kefa Cen (3 February 2014). "Experimental Investigation on Multiphase Bunsen Reaction in the Thermochemical Sulfur–Iodine Cycle". Industrial & Engineering Chemistry Research. 53 (8): 3021–3028. doi:10.1021/ie4038856.
- 1 2 Guo, H.F.; P. Zhang; Y. Bai; L.J. Wang; S.Z. Chen; J.M. Xu (3 June 2009). "Continuous purification of H2SO4 and HI phases by packed column in IS process". International Journal of Hydrogen Energy. 35 (7): 2836–2839. doi:10.1016/j.ijhydene.2009.05.009.
- ↑ Sella, Andrea (3 February 2012). "Karl Fischer's titrator". Chemistry World. Royal Society of Chemistry. Retrieved 2 January 2015.
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