Classification of common functional groups


functional groups

Functional groups play a decisive role in the properties of organic matter, -X, -OH, -CHO, -COOH, -NO2, -SO3H, -NH2, RCO-, these functional groups determine the halogenated hydrocarbons, alcohols or phenols, aldehydes in organic matter , carboxylic acids, nitro compounds or nitrites, sulfonic acid organics, amines, amides chemical properties. Therefore, learning the properties of organic substances is actually learning the properties of functional groups. Organic substances containing any functional groups should have the chemical properties of such functional groups. Organic substances that do not contain such functional groups do not possess the chemical properties of such functional groups. A point to be aware of in particular in chemistry. For example, aldehydes can undergo silver mirror reaction or be oxidized by freshly prepared copper hydroxide suspension, which can be considered as a more characteristic reaction of aldehydes; but this is not unique to aldehydes, but to aldehyde groups Therefore, all substances containing aldehyde groups, such as glucose, formic acid and formate, can undergo silver mirror reaction, or be oxidized by newly prepared copper hydroxide suspension.

Alkane: carbon-carbon single bond (C-C) (each C has a triple bond) [Note] carbon-carbon single bond is not a functional group,

·Olefin: carbon-carbon double bond (>C=C<) addition reaction, oxidation reaction. (Has a planar structure, that is, the double bond and the atoms to which it is attached are in the same plane).

·Alkynes: carbon-carbon triple bond (-C≡C-) addition reaction. (has a linear structure, that is, the triple bond and the atoms to which it is connected are in the same straight line).

Halogenated hydrocarbon: halogen atom (-X), X represents a halogen element (F, Cl, Br, I).

Alcohol, phenol: hydroxyl (-OH); primary alcohol hydroxyl can eliminate carbon-carbon double bond, phenolic hydroxyl can react with NaOH to generate water, react with Na2CO3 to generate NaHCO3, and both can react with metallic sodium to generate hydrogen.

·Ether: The ether bond (-C-O-C-) can be formed by dehydration of alcoholic hydroxyl groups. The simplest ether is methyl ether (dimethyl ether DME).

·Sulfide: (-S-) is easily oxidized to form sulfoxide or sulfone by reacting potassium sulfide (or sodium) with halogenated hydrocarbon or sulfate, and reacts with halogenated hydrocarbon to generate sulfonium salt (thionium salt). Under the influence of the sulfur atom in the molecule, the α-carbon atom can form carbon positive, negative ions or carbon free radicals.

·Aldehyde: Aldehyde group (-CHO); silver mirror reaction can occur, and it can be oxidized to carboxyl group by reaction with Fehling’s reagent. Addition with hydrogen generates hydroxyl.

· Ketone: carbonyl (>C=O); can be added with hydrogen to generate hydroxyl. Due to the strong electron-withdrawing nature of oxygen, nucleophilic addition reactions are prone to occur on carbon atoms. Other common chemical reactions include: nucleophilic reduction, aldol condensation.

Carboxylic acid: carboxyl group (-COOH); acidic, react with NaOH to generate water (neutralization reaction), react with NaHCO3 and Na2CO3 to generate carbon dioxide, and undergo esterification with alcohol.

·Ester: Esters (-COO-) are hydrolyzed under acidic conditions to generate carboxylic acids and alcohols (incomplete reaction), and under alkaline conditions to generate salts and alcohols (complete reaction).

· Nitro compounds: nitro (-NO2); nitroso (-NO).

·Amine: Amino (-NH2). Weakly basic.

·Sulfonic acid: Sulfo (-SO3H) acidity can be generated by substitution with concentrated sulfuric acid.

·Acyl: (-CO-) The reaction of introducing acyl groups into nitrogen, oxygen, carbon and other atoms in organic compound molecules is collectively referred to as acylation.

HO-NO2 nitric acid -NO2 nitroxyl HO-SO2-OH sulfuric acid R-SO2-sulfonyl.

·Nitrile: cyano (-C≡N) Alkali metal cyanide in cyanide is easily soluble in water and is alkaline when hydrolyzed.

· Hip: isocyano (-NC).

· Hydrazone: (=C=NNH2) the carbonyl of aldehyde or ketone is condensed with hydrazine or substituted hydrazine.

·Sulfhydryl: (-SH) weak acid, easily oxidized.

· Phosphine: (-PH2) Part or all of the hydrogen atoms of phosphine are replaced by hydrocarbon groups.

· Oxime: [(aldoxime:RH>C=N-OH)(ketoxime:RR’>C=N-OH)] Condensation of carbonyl group of aldehyde or ketone and amino group in hydrocarbon amine.

• Epoxy group: -CH(O)CH-.

· Azo: (-N=N-).

Aromatic rings (such as benzene rings) are characterized by easy electrophilic substitution and difficulty in addition reactions, and this large conjugated system generally has characteristic absorption peaks in the spectrum. Hydrogen generally has a strong deshielding effect.