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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 ...
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:
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.
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 ...
Ortho effect is an organic chemistry phenomenon where the presence of a chemical group at the at ortho position or the 1 and 2 position of a phenyl ring, relative to the carboxylic compound changes the chemical properties of the compound. This is caused by steric effects and bonding interactions along with polar effects caused by the various ...
Orthomolecular medicine[1][2] is a form of alternative medicine that claims to maintain human health through nutritional supplementation. It is rejected by evidence-based medicine. The concept builds on the idea of an optimal nutritional environment in the body and suggests that diseases reflect deficiencies in this environment.
The selectivity for functionalization of aromatic C–H bonds is governed by the general rule that the reaction does not occur ortho to a substituent when a C–H bond lacking an ortho substituent is available. [11] When only one functional group is present borylation occurs in the meta and para position in statistical ratios of 2:1 (meta:para).
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 ...