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Main arene substitution patterns. In ortho-substitution, two substituents occupy positions next to each other, which may be numbered 1 and 2. In the diagram, these positions are marked R and ortho. In meta-substitution the substituents occupy positions 1 and 3 (corresponding to R and meta in the diagram). In para-substitution, the substituents ...
Hammett equation. In organic chemistry, the Hammett equation describes a linear free-energy relationship relating reaction rates and equilibrium constants for many reactions involving benzoic acid derivatives with meta- and para- substituents to each other with just two parameters: a substituent constant and a reaction constant. [1][2] This ...
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 general rule for aromatic substitution is: ortho > meta > para. This gives non-selective β-blockers. Large para-substituents usually decrease activity but large ortho-groups retain some activity. Polysubstitution on carbon 2 and 6 makes the compound inactive but when the substitution is on carbon 3 and 5 there's some activity.
Ortho acid. In organic chemistry, ortho acids are organic, hypothetical chemical compounds having the structure R−C (OH)3 (R = alkyl or aryl). [1] Ortho acids themselves are unstable and cannot be isolated. However, ortho esters can be synthesized by the Pinner reaction, in which nitriles react with alcohols under acid catalysis:
Phosphoric acids and phosphates. Appearance. Pyrophosphoric acid. In chemistry, a phosphoric acid, in the general sense, is a phosphorus oxoacid in which each phosphorus (P) atom is in the oxidation state +5, and is bonded to four oxygen (O) atoms, one of them through a double bond, arranged as the corners of a tetrahedron.
The Kolbe–Schmitt reaction proceeds via the nucleophilic addition of a phenoxide, classically sodium phenoxide (NaOC 6 H 5), to carbon dioxide to give the salicylate. The final step is the reaction (protonation) of the salicylate anion with an acid to form the desired salicylic acids (ortho- and para- isomers).
An electron donating group (EDG) or electron releasing group (ERG, Z in structural formulas) is an atom or functional group that donates some of its electron density into a conjugated π system via resonance (mesomerism) or inductive effects (or induction)—called +M or +I effects, respectively—thus making the π system more nucleophilic. [1 ...