Nitro compounds are toxic, and their vapor can be absorbed by the human body through the skin, which makes people poisoned. Polynitro compounds are explosive.
Nitro compounds can be used as chemical raw materials and organic synthetic reagents in medicine, dyes, spices, explosives and other industries. Polynitro compounds are unstable in nature and strong in oxidation, and can be used as explosives. Such as trinitrotoluene (TNT) and picric acid.
Liquid nitro compounds have certain chemical stability, so they are often used as solvents for some organic reactions.
Structural formula: R-NO2
In the formula, R is aliphatic hydrocarbon group or aromatic hydrocarbon group, which are respectively called aliphatic nitro compound or aromatic nitro compound. According to the number of nitro groups, nitro compounds can be divided into monobasic, binary and polybasic nitro compounds.
Properties, physical properties, chemical properties, organic reaction, preparation, use and physical properties aliphatic nitro compounds are colorless or yellowish liquids with high boiling point. Aromatic nitro compounds are mostly yellow crystalline solids, and only mononitro compounds are high-boiling liquids. Because nitro group is a strong electron-withdrawing group, nitro compounds have large dipole moment, polarity and intermolecular attraction, and their boiling point is higher than that of corresponding halogenated hydrocarbons. Nitro compounds with chemical properties can be reduced to nitroso compounds, N- alkyl substituted hydroxylamines and amines in turn. N- hydroxy-substituted hydroxylamine and aromatic amine can be condensed with nitroso compounds in alkaline solution to produce oxidized azo compounds and azo compounds, and azo compounds can be reduced to 1, 2- dihydrocarbylhydrazine. When nitro compounds are reduced by reducing agents, primary amines can be obtained. It is made by nitration of alkanes at high temperature in industry. The product is a mixture of various nitro compounds and can be used as a solvent. Because of the different reducing agents and media, the products obtained by reduction of aromatic nitro compounds are also different, and the final product is aromatic primary amine when further reduced. Properties of aliphatic nitro compounds: 1, acidity of A-H Because nitro groups are strong electron-withdrawing groups, aliphatic nitro compounds A-H have certain acidity, dissolve in alkali and react with sodium hydroxide to form salts. The tautomerism between the acid form and nitro form of nitro compounds is similar to the keto-enol tautomerism of carbonyl compounds, and the main difference between them is that the acid form exists longer than the enol form. 3. Reaction with carbonyl compounds Primary and secondary nitro compounds with A-H can undergo condensation reaction with some carbonyl compounds under the catalysis of alkali. 4. Reaction with nitrite The primary nitroalkane reacts with nitrite to obtain blue nitroso compound, which is converted into red nitrosoxime salt solution under the action of alkali; Secondary nitroalkane reacts with nitrous acid to obtain colorless nitroso compound, and its alkaline solution is blue. Tertiary nitroalkane R3CNO2 does not react with nitrous acid because it has no a-h. Three nitroalkanes can be distinguished by this reaction. 5. Chemical properties of aromatic nitro compounds Because aromatic nitro compounds have no A-H, their properties are different from those of aliphatic nitro compounds. The most important property of aromatic nitro compounds is reduction reaction. Nitrobenzene is easily reduced in (1) reduction reaction. Nitrobenzene can be reduced to different products under different reducing agents and different conditions. (2) nucleophilic substitution reaction on aromatic ring The characteristic reaction of aromatic hydroxyl group is nucleophilic substitution reaction. When the hydrogen on the aromatic ring is replaced by nitro group, because nitro group is a strong electron-withdrawing group, the electron cloud density on the benzene ring decreases, which is not conducive to the attack of electrophile; At the same time, nitro groups also have great influence on other substituents on benzene ring. Halogenated aromatic hydrocarbons substituted by nitro groups in ortho or para position are prone to nucleophilic substitution reaction. Organic reactions Nitro compounds participate in many organic reactions. Hydrochloric acid can reduce aliphatic nitro compounds to amines with the help of iron as catalyst. Aliphatic nitro compounds hydrolyze to form aldehydes or ketones. Hydrogen can reduce aromatic nitro compounds to aniline under the catalysis of platinum. Aromatic nitro compounds are usually prepared by the reaction of nitric acid and sulfuric acid with corresponding organic molecules. Commonly used nitro compounds are trinitrophenol (picric acid), trinitrotoluene (TNT) and trinitrresorcinol (convergent acid). There are different ways to make nitro compounds in organic chemical industry. Nitro-hydroxyaldehyde reaction of aliphatic nitro compounds: prepared by the reaction of nitromethane and aldehyde; Michael reaction: nitromethane is prepared by addition of unsaturated carbonyl compounds; Michael reaction: nitrosoethylene is prepared by adding enol; Nucleophilic aliphatic substitution: preparation of haloalkyl sodium nitrite (NaNO2) substitute. Electrophilic substitution of aromatic nitro compounds: preparation by reaction of nitrous acid with aromatic compounds. Purpose Nitro compounds can be used as chemical raw materials and organic synthetic reagents in medicine, dyes, spices, explosives and other industries. Polynitro compounds are unstable in nature and strong in oxidation, and can be used as explosives. Such as trinitrotoluene (TNT) and picric acid. Aromatic nitro compounds are raw materials for preparing aromatic amines and diazonium salts. Polynitro compounds are explosive, such as 2,4,6-trimethyltoluene and trimethylphenol, which are very explosive compounds and can be used as explosives. Other polynitro compounds have strong fragrance and can be used to prepare artificial musk.