Naphthalene is an organic compound with the molecular formula C10H8. It is a white, volatile, and odorous crystal. It is produced in large quantities from coal tar, a byproduct of coking, and is used in the synthesis of dyes, resins, etc. The usual sanitary balls are made of naphthalene. Since 1958, the proportion of carbaryl used as a pesticide raw material has increased after it was put into production to replace chlorinated products such as DDT. The allocation of uses of naphthalene varies among countries, with approximately 70% being used for the production of phthalic anhydride and dye intermediates such as β－ Naphthol and rubber processing additives account for about 15%, insecticides account for about 6%, and tanning agents account for about 4%. Countries with less dye production, such as the United States, have a larger proportion of insecticides.
萘 - 理化性质
Naphthalene - Physical and Chemical Properties
Melting point 80.5 ℃, boiling point 217.9 ℃, freezing point 80.5 ℃, flash point 78.89 ℃, refractive index 1.58212 (100 ℃), constant volume combustion heat: 40.19KJ/g (standard atmospheric pressure, 298.15K), constant pressure combustion heat: 40205J/g (standard atmospheric pressure, 298.15K).
Insoluble in water, soluble in ethanol and ether, etc
Easy to evaporate and sublimate
After dissolving in ethanol, dropping it into water will result in white turbidity.
A mild oxidant yields quinone, while a strong oxidant yields anhydride. Naphthalene rings are more easily oxidized than side chains, so side chain oxidation cannot be used to produce naphthoic acid. Rings with high electron cloud density are prone to oxidation.
(2) Reduction of naphthalene
Naphthalene can be added with 5 H2 to form decahydronaphthalene.
(3) Addition of naphthalene
(4) Electrophilic substitution reaction of naphthalene
Naphthalene α- Bitwise ratio β- The site is more prone to electrophilic substitution reactions. α- Both resonance formulas have a complete benzene ring. β- There is only one resonance formula with a complete benzene ring in place of a substitution.
The electrophilic substitution mainly occurs on the naphthalene ring, similar to the benzene ring, but with stronger activity than the benzene ring
Start with the C next to the symmetrical two Cs in the middle, where the carbon activities of numbers 1, 4, 5, and 8 are exactly the same (referred to as α Carbon), carbon numbers 2, 3, 6, and 7 have identical properties (referred to as β Carbon).
In general, α Carbon activity greater than β Carbon, substituent in α In terms of position, this is controlled by dynamics. When the temperature is high, α The substituents on carbon  will transfer to β On carbon.
But in the Friedel-Crafterford acylation reaction of naphthalene, it was generated without heating α Bitwise sum β A mixture of bits. If nitromethane is used as a solvent, it mainly generates β Acylation products.
Modification: The two carbons in the middle are not numbered.
萘 - 萘的用途
The Use of Naphthalene Naphthalene
Widely used as a raw material for preparing dyes, resins, solvents, etc., and also as a repellent (commonly known as sanitary balls or camphor balls). Substitution reactions are easier than addition reactions.
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