Carboxylic acids. Representatives. Structure of carboxylic group and characteristic chemical reactions for carboxylic acids.
Explains the carboxyl group as a combined carbonyl and hydroxyl unit and why it behaves as a single functional group, then covers the acid strength of carboxylic acids and the factors that raise or lower it. Reactions are grouped into acid properties, nucleophilic substitution to derivatives such as esters, acid chlorides, anhydrides and amides, decarboxylation, reduction and oxidation, and substitution at the alpha carbon. The note closes with tables of saturated, unsaturated, dicarboxylic and aromatic representatives with their common and systematic names.
Topic 28 of 47 in the MU Pleven syllabus for Chemistry (Medicine, Year 1). The free AceMed note covers it in 8 sections, about 1,629 words (12 min of reading), with 15 flashcards.
In this note
CARBOXYLIC ACIDS. CHEMICAL REACTIONS OF CARBOXYLIC ACIDS. REPRESENTATIVES
I. Structure of the carboxyl group
II. Chemical properties of carboxylic acids
Decarboxylation
Reduction and oxidation of carboxylic acids
Substitution of the -hydrogen atoms
Substitution in aromatic ring
Representatives
I. Structure of the carboxyl group
Carboxylic acids contain the carboxyl functional group. The carboxyl group may be regarded as consisting of two groups: carbonyl >C=O and hydroxyl -OH. They are bonded together and affect strongly each other so that they behave as a new functional group, which is the cause of the new properties. The carbonyl -bond is polar, the carbon atom is considerably positively charged and it attracts electron density from the oxygen atom of the hydroxyl group. Thus the polarity of the O-H bond is increased. The effect becomes stronger because of the conjugation between the carbonyl -electrons and the unshared electron pair at the oxygen atom of the hydroxyl group
Therefore,the structure of the carbonyl group determines the considerable mobility of the hydrogenatom and acidic properties of these compounds.
Theproperties of the carboxyl group in aliphatic and aromatic carboxylic acids are essentiallythe same but the nature of the hydrocarbon group does influence some of the properties,e.g. acid strength.
On the other hand, the above described conjugation and inductive effects in the carboxyl group cause decreasing of the polarity of the carbonyl group and unlike typical carbonyl compounds (aldehydes and ketones), the carboxylic acids as well as their derivatives do not undergo nucleophilic addition, but undergo reactions of nucleophilic substitution.
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