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Naphthalene powder, the simplest condensed aromatic hydrocarbon, with the formula C10H8, is composed of two benzene rings sharing two adjacent carbon atoms. White crystalline powder, easy to volatilize, with mild aromatic smell, and crude naphthalene has coal tar odor. Insoluble in water, but soluble in absolute ethanol, ether and benzene. It is soluble in most organic solvents such as benzene, toluene, xylene, acetic acid, tetrahydronaphthalene, ether, acetone, carbon tetrachloride, carbon disulfide, methanol, ethanol, etc. Molten naphthalene is an excellent solvent for various organic compounds. Dyes such as indigo blue and nitroalizarin blue that are insoluble in organic solvents at room temperature can be soluble in molten naphthalene. Naphthalene dissolves most compounds containing phosphorus, sulfur and iodine. The solubility of naphthalene in water is very low. Naphthalene is widely used as raw material for preparing dyes, resins, solvents, etc., and also as insect repellent.
|
Chemical Formula |
C10H8 |
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Exact Mass |
128 |
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Molecular Weight |
128 |
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m/z |
128 (100.0%), 129 (10.8%) |
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Elemental Analysis |
C, 93.71; H, 6.29 |
Naphthalene powder, with the molecular formula C10H8, is the simplest polycyclic aromatic hydrocarbon composed of two adjacent carbon atoms fused together by two benzene rings. It is a white to off white crystalline powder with a melting point of 80.5 ℃ and a boiling point of 218 ℃. It has a special odor, is easily sublimated, and is insoluble in water but soluble in ethanol and ether. It is this unique chemical structure that endows naphthalene with extremely strong reactivity - it is prone to electrophilic substitution reactions, and its activity is even higher than that of benzene rings.
Core purpose:
The biggest use, undoubtedly, is the production of phthalic anhydride (abbreviated as phthalic anhydride). Globally, about 70% of naphthalene is used in this direction, making it the "absolute mainstay" of naphthalene consumption.
What is phthalic anhydride? It is a key raw material for plasticizers, unsaturated polyester resins, and alkyd resins. Using vanadium pentoxide as a catalyst and air as an oxidant at high temperatures, naphthalene can be directly oxidized to phthalic anhydride. This conversion efficiency is high and the process is mature, making it the most economically valuable conversion path for naphthalene.
The downstream products of phthalic anhydride have a wide coverage: plasticizers are used to soften plastics such as PVC, making them flexible; Unsaturated polyester resin is widely used in fiberglass, yachts, and automotive parts; Alkyd resin is an important base material in the coating industry. It can be said that without the naphthalene phthalic anhydride route, the modern plastics, coatings, and composite materials industries would lose an important pillar.
It is worth noting that phthalic anhydride can further generate phthalimide, which can be used to synthesize various high value-added chemicals, including certain engineering plastics and functional materials. This extended chain keeps the value of naphthalene rising towards the high-end.
Dye industry
It holds a significant position in the dye industry. Using naphthalene as raw material, a series of unit operations such as sulfonation, nitration, reduction, amination, and hydrolysis can be carried out to produce various key intermediates such as β - naphthol, α - naphthol, and naphthylamine. These intermediates are the core raw materials for synthesizing anthraquinone dyes, reactive dyes, dispersants, and water reducers.
Specifically:
β - Naphthol: It is the basis for manufacturing azo dyes and naphthol AS series dyes, widely used in textile dyeing and printing.
Naphthalene sulfonate: Naphthalene is converted into naphthalene sulfonate through sulfonation reaction, which then reacts with formaldehyde to form naphthalene sulfonate formaldehyde condensate. These compounds are not only diffusion agents and dispersants in dye production, but also the core components of concrete water reducers - they can significantly improve the plastic deformation ability of concrete without reducing its strength, and are called "super plastic materials".
Diffuser and water reducer: In the field of construction, naphthalene based water reducer is currently one of the most widely used high-efficiency water reducers, which can significantly improve the strength and durability of concrete and is an indispensable additive in modern construction engineering.
The usage of naphthalene in the dye industry varies among countries. Countries with less dye production, such as the United States, have significantly higher usage of naphthalene in the direction of insecticides, reflecting regional differences in naphthalene use allocation.
Medical field
It also plays an irreplaceable role in the pharmaceutical industry. Derivatives of naphthalene, such as naphthalene sulfonate compounds, are key intermediates in the synthesis of various drugs.
Non steroidal anti-inflammatory drugs (NSAIDs): Naphthalene is an important raw material for the synthesis of antipyretic and analgesic drugs such as indomethacin. Indomethacin is a widely used anti-inflammatory and analgesic drug in clinical practice, and its molecular skeleton contains a naphthalene ring structure.
Naphthylamine drugs: Naphthylamine can be synthesized from naphthalene through a series of reactions, and further used to synthesize antibiotics, antimalarials, and other drugs.
Alkaloids and pharmaceutical intermediates: Naphthalene powder can also be used to prepare various alkaloid compounds, providing rich molecular frameworks for new drug development.
It can be said that naphthalene is not only a chemical raw material, but also the "molecular Lego" of modern pharmaceutical chemistry - it provides a stable aromatic skeleton, on which chemists build a myriad of drug molecules.
Rubber and Plastic Industry
The use of naphthalene in the rubber and plastic industries is mainly concentrated in two directions: rubber anti-aging agents and plasticizers.
Rubber anti-aging agent: Naphthalene derivatives are important raw materials for manufacturing rubber anti-aging agents. Rubber products such as tires, hoses, and seals can age and crack due to oxidation during use. Naphthalene based anti-aging agents can effectively delay this process and significantly extend the service life of rubber products.
Plasticizers and resins: Naphthalene sulfonate formaldehyde condensate can be used as plasticizers and curing agents in plastic and resin manufacturing, endowing materials with better processing and mechanical properties. In addition, naphthalene is also a basic raw material for the production of synthetic resins, plasticizers, and surfactants, widely used in coatings, inks, and plastic products.
Civilian and daily use
When it comes to naphthalene, many people's first reaction is "sanitary balls". That's right, the most well-known civilian use of naphthalene is to manufacture camphor balls (insect repellents). The easy sublimation property of naphthalene enables it to continuously release steam, effectively repelling pests and ants in the wardrobe.
However, it should be noted that in 1993, China officially banned the use and sale of naphthalene pills.
The reason is that naphthalene has certain toxicity - the lowest lethal dose (LDLo) for humans is 100mg/kg (children) and 29mg/kg (adults) orally, and the LD50 for rats is 490mg/kg orally. Long term exposure to low concentrations can cause an increase in liver transaminase, damage liver function, and have adverse effects on blood components. Therefore, modern home pest control has gradually been replaced by safer alternatives such as dichlorobenzene.
In addition, naphthalene is also used as a leather anti mold preservative and wood protectant, and still has certain applications in the industrial field.
Electronics and Emerging Fields
The application of naphthalene in the electronics industry is mainly reflected in the manufacturing of electronic components such as capacitors and resistors. The high vapor density (4.4, relative to air) and stable electrochemical properties of naphthalene give it unique advantages in certain specialized electronic components.
More noteworthy is the cutting-edge application of naphthalene - PEN (polyethylene naphthalate).
PEN is a high-performance engineering plastic with superior heat resistance, barrier properties, and mechanical strength compared to ordinary PET. Japan regards PEN as the main area of future demand growth for naphthalene, and its development depends on the degree of breakthrough in production technology. At present, multiple companies around the world are actively researching and developing PEN production processes. Once the technology matures, the demand for naphthalene will usher in a new round of growth.
Preparation of naphthalene powder:
Naphthalene accounts for approximately 8% to 12% of high-temperature coal tar. Distillation of coal tar, cutting of kerosene, removal of phenol and quinoline, and distillation to obtain finished naphthalene. Each ton of naphthalene consumes 10 tons of coal tar.
Catalytic reforming oil, catalytic cracking light cycle oil, tar by-products from cracking into ethylene, etc.
Naphthalene used in the raw material industry is rapidly cooled in a crystallization box, then cooled to 82 ° C, uniformly cooled, and then cooled at a cooling rate of 2 ° C/h to 60 ° C. For the first time, naphthalene crystal oil rich in sulfones is discharged as a middle distillate for post-treatment.
Then, the material inside the crystallization box is heated at a rate of 4 ° C/h, sampled every 0.5 hours, and its crystallization point is measured.
According to different crystallization points, they are discharged into corresponding distillation tanks, so 3-4 fractional crystallization can be carried out to obtain high-purity refined naphthalene.
The production process system considers large cycles as production cycles. Each major cycle consists of four sub cycles, with each sub cycle containing 4-6 segments.
Each stage consists of three steps: crystallization, partial melting, and full melting. Example of falling film crystallization process: The liquid industrial naphthalene sent out by the industrial naphthalene unit is sent into the distillate tank.
When the fourth stage crystallization operation is completed, the liquid supply in the tank is pumped into the dynamic crystallization collection tank.
Uncrystalline naphthalene oil and sweat are placed in a distillation tank with lower purity, and the entire melt can be used as raw materials for the fifth stage.
After six crystallization stages, naphthalene can be obtained by refining according to the predetermined procedure.
To improve the extraction rate of naphthalene, the portion rich in thionaphthalene can be sent to a static crystallizer for treatment. The static crystallization product will be returned to the corresponding distillation tank of the dynamic crystallization system, and the residual liquid can be sold as a water reducing agent. Due to the simultaneous use of dynamic and static crystallizers in the device, not only can the naphthalene recovery rate be improved, but energy consumption can also be reduced.
Chemical properties of naphthalene:
A mild oxidant yields quinone, and a strong oxidant yields anhydride. Naphthalene ring is easier to be oxidized than side chain, so naphthoic acid cannot be prepared by side chain oxidation. The rings with high electron cloud density are easy to be oxidized. for example α- Nitro naphthalene is oxidized to 3-nitrophthalic anhydride, α- Naphthylamine is oxidized to phthalic anhydride (the ring of amino group is oxidized).
Naphthalene can be added with 5 hydrogen to form decalin.
Naphthalene α- Bit ratio β- The electrophilic substitution reaction is more likely to take place in the. α- Both of the two resonances have complete benzene rings. β- There is only one resonance type with complete benzene ring.
The electrophilic substitution mainly occurs on the naphthalene ring, which is the same as the benzene ring (easy to replace, difficult to add), but is more active than the benzene ring.
Start from the C next to the two symmetrical C in the middle (the two carbon in the middle are not numbered). Among them, carbon 1, 4, 5 and 8 have the same activity (called α Carbon), No. 2, 3, 6 and 7 carbon have the same properties (called β Carbon).
Normally, α Carbon activity greater than β Carbon, substituent in α This is controlled by dynamics. When the temperature is high naphthalene powder. α The substituents on the carbon will be transferred to β On carbon.
However, the Friedel Crafts acylation reaction of naphthalene generates α Bitsum β A mixture of bits. If nitromethane is used as solvent, it mainly generates β Acylation products.
Frequently Asked Questions
What does naphthalene smell like?
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Naphthalene-the active chemical in traditional mothballs-has a strong, highly distinct, and pungent chemical odor. It is often described as smelling sharp and acrid, with noticeable similarities to gasoline, wood tar, or the heavy chlorine from an indoor swimming pool.
What is the common name for naphthalene?
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Naphthalene's most common names in everyday consumer products are mothballs and moth flakes. In industrial and chemical contexts, it is frequently referred to as white tar, tar camphor, or naphthalin.
Are mothballs the same as naphthalene?
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Mothballs in the U.S. contain very high concentrations of the chemical naphthalene or paradichlorobenzene as active ingredients. They are meant to be used in closed, airtight containers so that the fumes they produce are trapped. The trapped fumes build up and kill any clothes moths inside.
What is naphthalene used for?
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Naphthalene is a strong-smelling, flammable white solid primarily used as an industrial building block and an active ingredient in pest repellents.
Is naphthalene harmful to humans?
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Yes, naphthalene is highly toxic to humans. Exposure to high levels-whether through breathing in vapors, touching it, or accidentally swallowing it-can cause serious and immediate health consequences.
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