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Bromotoluenes are aryl bromides based on toluene in which at least one aromatic hydrogen atom is replaced with a bromine atom. They have the general formula C 7 H 8– n Br n , where n = 1–5 is the number of bromine atoms.
The presence of alkoxyl or related chelating groups accelerates lithium–halogen exchange. [3] Lithium halogen exchange is typically a fast reaction. It is usually faster than nucleophilic addition and can sometimes exceed the rate of proton transfer. [4] Exchange rates usually follow the trend I > Br > Cl.
Toluene (/ ˈ t ɒ l. j u iː n /), also known as toluol (/ ˈ t ɒ l. j u. ɒ l , - ɔː l , - oʊ l / ), is a substituted aromatic hydrocarbon [ 15 ] with the chemical formula C 6 H 5 CH 3 , often abbreviated as PhCH 3 , where Ph stands for the phenyl group.
Ion-exchange resin beads Ion-exchange column used for protein purification. Ion exchange is a reversible interchange of one species of ion present in an insoluble solid with another of like charge present in a solution surrounding the solid. Ion exchange is used in softening or demineralizing of water, purification of chemicals, and separation ...
tert-Butyllithium or n-butyllithium are the most commonly used reagents for generating new organolithium species through lithium halogen exchange. Lithium–halogen exchange is mostly used to convert aryl and alkenyl iodides and bromides with sp2 carbons to the corresponding organolithium compounds. The reaction is extremely fast, and often ...
Therefore, they are generated by adding iron filings to bromine or chlorine. Here is the mechanism of this reaction: The mechanism for bromination of benzene. The mechanism for iodination is slightly different: iodine (I 2) is treated with an oxidizing agent such as nitric acid to obtain the electrophilic iodine ("I +", probably IONO 2).
The methyl group in toluene is small and will lead the ortho product being the major product. On the other hand, the t-butyl group is very bulky (there are 3 methyl groups attached to a single carbon) and will lead the para product as the major one. Even with toluene, the product is not 2:1 but having a slightly less ortho product.
Specially activated magnesium, such as Rieke magnesium, circumvents this problem. [5] The oxide layer can also be broken up using ultrasound, using a stirring rod to scratch the oxidized layer off, [6] or by adding a few drops of iodine or 1,2-Diiodoethane. Another option is to use sublimed magnesium or magnesium anthracene. [7]