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Halogenation of benzene where X is the halogen, catalyst represents the catalyst (if needed) and HX represents the protonated base. A few types of aromatic compounds, such as phenol, will react without a catalyst, but for typical benzene derivatives with less reactive substrates, a Lewis acid is required as a catalyst.
A further example of insertion into a closo carborane is the synthesis of the yellow-orange solid closo-1,2,3-(CO) 3 FeC 2 B 4 H 6: closo−C 2 B 4 H 8 + Fe 2 (CO) 9 → closo−(CO) 3 FeC 2 B 4 H 6 + Fe(CO) 5 + CO. A closely related reaction involves the capping of an anionic nido carborane C 2 B 4 H − 7. closo−C 2 B 4 H 8 + NaH → Na ...
Aromatic compounds are subject to electrophilic halogenation: R−C 6 H 5 + X 2 → HX + R−C 6 H 4 −X. This kind of reaction typically works well for chlorine and bromine. Often a Lewis acidic catalyst is used, such as ferric chloride. [7] Many detailed procedures are available.
The cyclic compound borepin has been isolated and is aromatic. Boron-boron multiple bonds are rare, although doubly-bonded dianions have been known since the 1990s. [20] Neutral analogues use NHC adducts, such as the following diborane(2) derivative: [21] [22] Each boron atom has an attached proton and is coordinated to a NHC carbene. [23] [24]
Carborane acids H(CXB 11 Y 5 Z 6) (X, Y, Z = H, Alk, F, Cl, Br, CF 3) are a class of superacids, [1] some of which are estimated to be at least one million times stronger than 100% pure sulfuric acid in terms of their Hammett acidity function values (H 0 ≤ –18) and possess computed pK a values well below –20, establishing them as some of the strongest known Brønsted acids.
DDQ and an acid catalyst has been used to synthesise a steroid with a phenanthrene core by oxidation accompanied by a double methyl migration. [9] In the process, DDQ is itself reduced into an aromatic hydroquinone product. Sulfur and selenium are traditionally used in aromatization, the leaving group being hydrogen sulfide. [10]
The most commonly employed Sandmeyer reactions are the chlorination, bromination, cyanation, and hydroxylation reactions using CuCl, CuBr, CuCN, and Cu 2 O, respectively. More recently, trifluoromethylation of diazonium salts has been developed and is referred to as a 'Sandmeyer-type' reaction.
The icosahedral charge-neutral closo-carboranes, 1,2-, 1,7-, and 1,12- C 2 B 10 H 12 (informally ortho-, meta-, and para-carborane) are particularly stable and are commercially available. [10] [11] The ortho-carborane forms first upon the reaction of decaborane and acetylene. It converts quantitatively to the meta-carborane upon heating in an ...