3-hydroxypyridine

3-Carboxypyridine, also known as niacin, is a crucial organic compound with many main uses.
In the field of medicine, 3-carboxypyridine plays a key role. If the human body lacks this substance, it will suffer from pellagra and other diseases. Because it can participate in the metabolism of the human body, it is indispensable for maintaining the normal function of the skin, digestive system and nervous system. Therefore, it is often used in pharmaceutical preparations to prevent and treat niacin deficiency.
In the food industry, 3-carboxypyridine also plays an important role. As a food nutrient enhancer, it can be added to various foods to enhance the nutritional value of food. Many cereal foods, infant foods, etc., are added with appropriate amounts of 3-carboxypyridine to meet the human body's demand for this nutrient.
In the field of feed, 3-carboxypyridine is also a commonly used additive. Added to animal feed, it can promote animal growth and development, enhance animal immunity, improve feed utilization, and then improve breeding efficiency.
In the chemical industry, 3-carboxypyridine is an important organic synthesis raw material. Through a series of chemical reactions, it can synthesize a variety of compounds with special functions, such as pyridine drugs, pesticides, dyes, etc. Some pesticides synthesized with it as raw materials have efficient control effects on pests and are less harmful to the environment; some dyes synthesized have bright colors and excellent fastness.

3-Aminopyridine is an organic compound with many physical properties. It is a colorless to light yellow liquid and exists stably at room temperature and pressure. Looking at its color, it is colorless when pure, but it may appear light yellow due to impurities or storage conditions. It has a unique smell. This smell is similar to the special smell of pyridine compounds, but the smell of 3-aminopyridine may be slightly lighter than that of pyridine.
When it comes to the melting point, the melting point of 3-aminopyridine is about 61-63 ° C, and the boiling point is 254-255 ° C. This boiling point characteristic makes it undergo phase transition in a specific temperature range. Above the melting point, it melts from a solid state to a liquid state; when it reaches the boiling point, it gasifies from a liquid state to a gaseous state.
In terms of solubility, 3-aminopyridine is soluble in water, and it is also easily soluble in organic solvents such as ethanol and ether. When dissolved in water, it forms hydrogen bonds with water molecules and interacts with water molecules, showing a certain solubility. In organic solvents, it can be uniformly dispersed and miscible with organic solvents due to the principle of similar miscibility.
In terms of density, 3-aminopyridine has a density of about 1.129 g/mL. This means that the mass of 3-aminopyridine per unit volume is relatively stable. This density characteristic is of great significance for material measurement and separation in chemical production and experimental operations.
In addition, 3-aminopyridine is basic and can react with acids to form corresponding salts due to the presence of amino groups. This basic property is often used as a base catalyst or participates in acid-base neutralization reactions in organic synthesis, providing the possibility for the synthesis of specific organic compounds. In short, the physical properties of 3-aminopyridine lay the foundation for its application in chemical, pharmaceutical, materials and other fields.

3-Carboxylpyridine is a compound with a carboxyl group attached to a pyridine ring. Its chemical properties are unique and worth exploring.
This compound is acidic. The Gain carboxyl group can ionize hydrogen ions and exhibit acidic properties in aqueous solutions. Its acidity is related to the chemical environment in which the carboxyl group is located. The electronic effect of the pyridine ring can affect the ionization of the carboxyl group. If the pyridine ring has an electron-withdrawing group, the acidity of the carboxyl group will be enhanced; if it is a donating group, the acidity will be weakened.
3-carboxylpyridine can participate in the esterification reaction. Under suitable catalyst and reaction conditions, the carboxyl group can react with alcohols to form corresponding esters. This reaction is a reversible reaction. By controlling the reaction conditions, such as temperature, catalyst dosage and ratio of reactants, the reaction equilibrium can be adjusted and the yield of esters can be improved.
Furthermore, the existence of the pyridine ring makes 3-carboxypyridine alkaline to a certain extent. The lone pair of electrons on the nitrogen atom of the pyridine ring accepts protons and exhibits alkalinity under certain conditions. However, due to the acidic effect of the carboxyl group, its alkalinity is relatively weak. This basic property makes it possible to neutralize with acids to form corresponding salt compounds. The chemical properties of
3-carboxypyridine make it widely used in the field of organic synthesis. It can be used as a key intermediate to prepare many organic compounds with biological activity or special functions. With its acidic, alkaline and esterifiable properties, it can design various reaction paths and construct complex organic molecular structures, which is of great value in the fields of medicinal chemistry and materials science.

There are various methods for the synthesis of 3-carboxylpyridine. The following are common methods:
First, pyridine is used as the starting material and obtained by oxidation reaction. If a strong oxidizing agent, such as potassium permanganate and potassium dichromate, is selected under suitable catalysts and specific reaction conditions, pyridine can be oxidized, and carboxyl groups can be introduced into its rings, which is a more classic way. However, this process requires strict control of the reaction conditions. Due to the degree of oxidation, it is easy to cause excessive oxidation, which affects the purity and yield of the product.
Second, pyridine is prepared by carboxylation of halogenated pyridine. First, pyridine is halogenated to introduce halogen atoms, and then under suitable reagents and conditions, such as a Grignard reagent made of metallic magnesium, and then reacted with carbon dioxide, the halogen atoms can be converted into carboxyl groups. This path has a little more steps, but the reaction is relatively easy to control, and the reaction conditions are not extremely strict.
Third, a compound containing carboxyl groups and pyridine structures is used as a raw material, and the structure is modified by a specific chemical reaction. For example, if the carboxyl group in the raw material can be converted into a pyridine ring through a specific reaction, or the pyridine ring can be reacted to a carboxyl group without affecting the structure and properties of other groups, it is also a feasible method. However, the selection of such raw materials is crucial, depending on the characteristics and reaction feasibility of the specific compound.
Fourth, synthesis by coupling reaction catalyzed by transition metals. Such as palladium-catalyzed reactions, substrates containing pyridine structures can be coupled with reagents containing carboxyl groups or groups that can be converted into carboxyl groups in suitable ligands, bases and reaction solvents to construct 3-carboxyl pyridine structures. This method has high efficiency and good selectivity, and is increasingly used in modern organic synthesis. However, the optimization of catalyst cost and reaction conditions needs to be considered.

In today's market, the price of sturgeon varies depending on the species and quality.
The price of commonly farmed sturgeon is about 20 to 30 yuan to 70 to 80 yuan per catty. This kind of sturgeon is mostly raised in ponds and fed in the usual way. It grows faster, and the meat is thick and fat. Although it tastes beautiful, it is not a treasure. Therefore, the price is easy, and it is common in the market. The common people can buy it and eat it.
As for wild sturgeon, or special varieties such as Chinese sturgeon, it is strictly protected by the state. It is prohibited from being caught and sold in the city. Chinese sturgeon, which travels back to rivers and rivers for thousands of years, has a very high price for scientific research and culture. If it is illegally traded, it will be severely punished.
There are also sturgeons for caviar, such as the European sturgeon. Because the roe is more expensive than gold, the price of the sturgeon body is also higher. This kind of sturgeon is not easy to raise, and needs proper temperature and water. Careful care, its price can reach hundreds of yuan per catty, or even higher, and it is mostly used for high-end catering and foreign trade.
There are also small sturgeon species for ornamental use. Although they are not edible, they are different in shape and beauty, and the price varies from product to product, or tens of yuan per tail, or hundreds of yuan, which is popular with aquarium enthusiasts. < Br >
is based on the price of sturgeon in the market, ranging from tens of yuan to hundreds of yuan, all of which vary according to species, uses, and maintenance methods. Buyers should be aware of their feelings and choose them.