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The starting point for the collection of the substituent constants is a chemical equilibrium for which the substituent constant is arbitrarily set to 0 and the reaction constant is set to 1: the deprotonation of benzoic acid or benzene carboxylic acid (R and R' both H) in water at 25 °C. Scheme 1. Dissociation of benzoic acids
When a substituent group is located ortho position to the carboxyl group in a substituted benzoic acid compound, the compound becomes more acidic surpassing the unmodified benzoic acid. Generally ortho-substituted benzoic acids are stronger acids than their meta and para isomers.
p-Anisic acid, also known as 4-methoxybenzoic acid or draconic acid, is one of the isomers of anisic acid. The term "anisic acid" often refers to this form specifically. [ 1 ] It is a white crystalline solid which is insoluble in water, highly soluble in alcohols, and soluble in ether and ethyl acetate .
In organic chemistry, a methoxy group is the functional group consisting of a methyl group bound to oxygen. This alkoxy group has the formula R−O−CH 3 . On a benzene ring , the Hammett equation classifies a methoxy substituent at the para position as an electron-donating group , but as an electron-withdrawing group if at the meta position.
This can also explain why phosphorus in phosphanes can't donate electron density to carbon through induction (i.e. +I effect) although it is less electronegative than carbon (2.19 vs 2.55, see electronegativity list) and why hydroiodic acid (pKa = -10) being much more acidic than hydrofluoric acid (pKa = 3).
Anisic acid or methoxybenzoic acid is an organic compound which is a carboxylic acid. It exists in three forms, depending on arene substitution patterns:
Alkoxy groups Aryloxy groups. In chemistry, the alkoxy group is an alkyl group which is singularly bonded to oxygen; thus R−O.Denoted usually with apostrophe('). The range of alkoxy groups is vast, the simplest being methoxy (CH 3 O−). [1]
Directed metallation is not limited to lithium intermediates or even to an ortho preference. In one study [13] it is found that the reaction product of N,N-dimethylaniline with a complex of TMEDA, sodium salt of TMP and di-tert-butylzinc is a meta zincated complex as a stable crystalline compound.