5-fluoro-2-pyridinecarboxylic acid

5-Hydroxy-2-pentenoic acid, this is also an organic compound. Its main uses are many. Although this specific compound is not detailed in books such as Tiangong Kaiwu, it is deduced from the idea of ancient chemical technology and application, or it can be considered as follows.
In the field of chemical synthesis, 5-hydroxyl-2-pentenoic acid may be used as a key intermediate. Because of its structural characteristics of both hydroxyl groups and enoic acids, hydroxyl groups can undergo esterification, etherification and other reactions, and the enoic acid part can participate in many reactions such as addition and polymerization. With this as the starting material, a series of delicate transformations can be prepared to produce a wide variety of organic compounds. For example, by esterification with alcohols, corresponding ester products can be obtained. Such esters may have important applications in flavors, solvents and other industries. Among fragrances, some esters can impart a unique aroma to the product; when used as a solvent, its solubility and volatility or meet specific process requirements.
In the field of pharmaceutical chemistry, the special structure of 5-hydroxy- 2-pentenoic acid may give it a certain biological activity. Or it can be used as a lead compound, chemically modified and optimized to develop drugs with therapeutic effect. Although there was no modern advanced drug development system in ancient times, the exploration of the medicinal value of natural products has been going on for a long time. By analogy, if this compound exists in some natural products, the ancients may have noticed its subtle effects on human function in practice.
In the field of materials science, due to its reactive groups, it can be used to prepare polymer materials with unique properties. Through polymerization, its structural units are introduced into the polymer chain, thereby endowing the material with special physical and chemical properties, such as improving the flexibility and hydrophilicity of the material. Although the ancient material preparation technology is relatively simple, it can also be speculated about its potential application direction by retrospecting with modern material design concepts.
In summary, although 5-hydroxy- 2-pentenoic acid has not been directly recorded in ancient books, it has considerable application potential in the fields of chemical industry, medicine, materials, etc.

The synthesis of 5-hydroxy-2-pentanoic acid can be achieved by the following methods.
First, glutaric anhydride is used as the starting material. First, the glutaric anhydride is reacted with lithium aluminum hydride in a suitable solvent at low temperature and in a nitrogen-protected atmosphere, and the carbonyl group of the glutaric anhydride is reduced to an alcoholic hydroxyl group to generate 5-hydroxyvaleric acid. Subsequently, the 5-hydroxyvaleric acid is reacted with p-toluenesulfonyl chloride in a pyridine solvent, and the hydroxyl group is replaced by a p-toluenesulfonyloxy group to form a well-reactive leaving group. Then, under the action of strong bases such as potassium tert-butanol, an intramolecular elimination reaction occurs to obtain 5-hydroxyl-2-pentenoic acid. Although there are many steps in this process, the reaction conditions of each step are relatively mild and the yield is considerable.
Second, acrylic acid and 3-chloro-1-propanol are used as raw materials. In the presence of bases such as potassium carbonate, the chlorine atom of 3-chloro-1-propanol reacts with the carboxyl anion of acrylic acid to generate 3- (acryloxy) -1-propanol. After that, through the ozonation reaction, and then through the reductive hydrolysis, the double bond is broken to form an aldehyde group, and the aldehyde group is further oxidized to a carboxyl group, and 5-hydroxy- 2-pentenoic acid can be prepared. The raw materials for this method are relatively easy to obtain, but the ozonation step needs to be handled with caution and requires high equipment.
Third, diethyl malonate and 3-bromo-1-propylene are used as starting materials. Under the catalysis of sodium ethyl glycol, the methylene malonate and 3-bromo-1-propylene undergo nucleophilic substitution. Next, the hydrolysis and decarboxylation reaction is carried out, first hydrolyzed into malonate monoester under basic conditions, then decarboxylated by acidification heating, and finally the product is hydroxylated. For example, osmium tetroxide and other reagents can be used to obtain the target product 5-hydroxyl-2-pentenoic acid. This route uses the classic diethyl malonate reaction, which is relatively mature, but attention should be paid to the control of the reaction conditions at each step to improve the yield.

5-Hydroxy-2-pentenoic acid is an organic compound with unique physical properties, which is now referred to in ancient Chinese.
In terms of its color state, at room temperature, 5-hydroxy-2-pentenoic acid is mostly colorless to light yellow liquid, clear and with a certain fluidity. It looks like a clear spring, but the chemical properties it contains are not as simple as it appears.
When it comes to smell, this thing emits a weak and special smell, which is neither rich and fragrant, nor pungent and intolerable, but when you smell it carefully, you can feel its unique smell, just like a different charm hidden in the ordinary world.
The boiling point of 5-hydroxy- 2-pentenoic acid is about a specific temperature range. When the external temperature gradually rises to a certain value, the molecules gain energy and break free from each other, and gradually change from liquid to gaseous. The existence of this boiling point makes it change its shape under a specific temperature environment, which is of great significance in many fields such as chemical industry.
Its melting point is also an important physical property. Under certain low temperature conditions, the activity of 5-hydroxy- 2-pentenoic acid molecules slows down, and they are arranged in an orderly manner close to each other. The transition temperature is the melting point.
Furthermore, solubility is also the key. 5-Hydroxy-2-pentenoic acid exhibits different solubility in water and some organic solvents. In water, it has a certain solubility. Although it is not completely miscible, it can form a mixed system with water to some extent. In organic solvents such as ethanol and ether, its solubility is better and it can be fused with it. This property provides convenience for its chemical synthesis, separation and purification operations. According to this property, it can be skillfully treated and applied with different solvents.

The price of acetic acid is always on everyone's mind. I have heard of many people, saying that the change of this price is related to many ends.
At this moment, the market conditions are fickle, and the number of supply and demand determines the price. If there are many people who want it, but there are few people who supply it, the price will rise; on the contrary, if the supply exceeds the demand, the price will drop. And the weather, geographical location, and personnel are also related to the price. The weather is not smooth, the farmers are damaged, and the raw materials are rare, and the price will also increase; the geographical location is convenient, and the production is numerous, and the price may be flat. Personnel, the leniency of government orders, and the calculation of merchants can all make the price fluctuate.
Remembering the past, there was a severe drought in a certain year, the production of raw materials dropped sharply, and the price of acetic acid in the market was swaying up, and merchants hoarded it, waiting for the price to be sold, and the people could not get it if they wanted it, and it was miserable. Another year, the origin was bumper, the supply was sufficient, the price was stable, and it was easy for everyone to ask for it.
As for the present, according to the people of the city, the supply and demand are slightly flat recently, and the price is relatively stable. However, everyone still needs to observe the changes in the four directions, the omens of the times, and the issuance of decrees to prevent sudden changes in prices. Merchants should judge the situation and make good calculations to seek stability in profits; the people should also pay attention to the market to prepare for emergencies. The change of price, although impermanent, can be calmly responded to by observing its causes and understanding its reasons.

As recorded in "Tiangong Kaiwu", the storage conditions of sulfuric acid contained in river water are quite exquisite.
Sulfuric acid is strong and highly corrosive, so it is necessary to choose a well-made vessel to store it. In ancient times, special ceramic containers were often used, because of their dense texture, they can resist the erosion of sulfuric acid. The quality of ceramics can prevent the leakage of sulfuric acid, and the chemical properties are stable. It does not chemically react with sulfuric acid and maintains its purity.
The environment in which the reservoir is located is also crucial. It must be placed in a cool and dry place, protected from direct sunlight and humid gas. Direct sunlight can cause sulfuric acid to heat up, accelerate its volatilization and qualitative change; humid gas can easily rust the outer wall of the reservoir, damage its seal, and cause sulfuric acid leakage.
Furthermore, the storage place should be well ventilated. The volatile gas of sulfuric acid is highly toxic. If it accumulates and does not disperse, it is harmful to humans and animals. Good ventilation can make the volatile gas dissipate quickly and avoid disasters.
At the same time, the storage place of sulfuric acid should be kept away from fire sources and flammable materials. Sulfuric acid can easily cause violent reactions or even explosions when exposed to open flames or hot topics, endangering the safety of the surrounding area.
To sum up, the storage of sulfuric acid requires special ceramic containers, placed in a cool, dry, well-ventilated place away from flammable materials from fire sources, to ensure its safety and store its quality.