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In organic chemistry, nitration is a general class of chemical processes for the introduction of a nitro group (−NO2) into an organic compound. The term also is applied incorrectly to the different process of forming nitrate esters (−ONO2) between alcohols and nitric acid (as occurs in the synthesis of nitroglycerin).
Electrophilic aromatic substitution (SEAr) is an organic reaction in which an atom that is attached to an aromatic system (usually hydrogen) is replaced by an electrophile. Some of the most important electrophilic aromatic substitutions are aromatic nitration, aromatic halogenation, aromatic sulfonation, alkylation Friedel–Crafts reaction and ...
The nitronium ion, [NO 2] +, is the active reagent in aromatic nitration reactions. Since nitric acid has both acidic and basic properties, it can undergo an autoprotolysis reaction, similar to the self-ionization of water: 2 HNO 3 ⇌ [NO 2] + + NO − 3 + H 2 O
In electrophilic substitution in aromatic compounds, an atom appended to the aromatic ring, usually hydrogen, is replaced by an electrophile. The most important reactions of this type that take place are aromatic nitration, aromatic halogenation, aromatic sulfonation and acylation and alkylating Friedel-Crafts reactions. It further consists of ...
Nitrosation is typically performed with nitrous acid, formed from acidification of a sodium nitrite solution. Nitrous acid is unstable, and high yields require a rapid reaction rate; NO + synthon transfer is catalyzed by a strong nucleophile, such as (in increasing order of efficacy) chloride, bromide, thiocyanate, or thiourea.
The nitration product produced on the largest scale, by far, is nitrobenzene. Many explosives are produced by nitration including trinitrophenol (picric acid), trinitrotoluene (TNT), and trinitroresorcinol (styphnic acid). [3] Another but more specialized method for making aryl–NO 2 group starts from halogenated phenols, is the Zinke nitration.
A reaction modification with an aromatic phenyl ester as a reactant is called the Fries rearrangement. In the Scholl reaction two arenes couple directly (sometimes called Friedel–Crafts arylation). [22] In the Blanc chloromethylation a chloromethyl group is added to an arene with formaldehyde, hydrochloric acid and zinc chloride.
Contents. Electrophilic aromatic directing groups. In electrophilic aromatic substitution reactions, existing substituent groups on the aromatic ring influence the overall reaction rate or have a directing effect on positional isomer of the products that are formed. An electron donating group (EDG) or electron releasing group (ERG, Z in ...