4-pyridinecarboxylic acid, 3-chloro-2-fluoro-

Mercury, commonly known as mercury, is a liquid metal that is liquid at room temperature and pressure. Mercury has many unique physical properties.
First, mercury has a high density of about 13.6 grams per cubic centimeter, which makes it heavier than most common substances. Because of its high density, it can maintain a relatively stable liquid form in the container, unlike low-density liquids such as water, which are easy to flow and splash.
Second, the melting point of mercury is extremely low, only -38.87 ° C, which is why it appears liquid at room temperature. In contrast, its boiling point is 356.6 ° C. This range between the melting point and the boiling point allows mercury to remain liquid over a wide temperature range. This property is widely used in industry and scientific research.
Third, mercury has good electrical and thermal conductivity. Like many metals, mercury can play an important role in circuit conduction and heat transfer. In some special electronic devices, mercury's electrical conductivity can meet specific circuit requirements.
Fourth, mercury has a metallic luster, which can show a bright silver luster under the illumination of light. This optical property makes it useful for some decorative purposes or optical instruments.
Fifth, the surface tension of mercury is large, and on a clean plane, mercury droplets can maintain a relatively regular spherical shape, which is not easy to spread out. This property is related to its density and intermolecular forces. In specific experiments and industrial processes, it has a certain impact on the operation and application of mercury.

Mercury, bromine, and iodine are all halogen elements, and their chemical properties are unique.
Mercury, which is a liquid at room temperature, is a metal element. Its chemical properties are relatively stable, and it is not easy to react quickly with common substances such as oxygen at room temperature. However, under heating conditions, it can combine with oxygen to form mercury oxide. Mercury can dissolve many metals to form amalgam, which is used in metallurgy and other fields. And mercury has certain toxicity, and special caution is required when using it.
Bromine, a dark reddish-brown liquid at room temperature, is volatile and has a strong pungent odor. Bromine is chemically active and highly oxidizing. It can react with metals, such as iron to form iron bromide. In organic chemistry, bromine is often used as an important reagent for addition, substitution and other reactions, such as addition reaction with olefins to form dibromogens.
Iodine, a purple-black solid at room temperature, is easy to sublimate. The oxidation of iodine is slightly weaker than that of bromine, but it can also react with many metals. It is also widely used in organic synthesis. Iodine is essential to human health and is a key raw material for thyroid hormone synthesis. Iodine deficiency can cause diseases such as thyroid enlargement.
Although these three elements belong to the halogen group, due to differences in atomic structure, there are differences in chemical properties, such as the degree of reactivity, etc., and it has great significance in human life and industrial production.

Hydrogen, oxygen, and nitrogen are the main components of the atmosphere, and water is formed by the combination of hydrogen and oxygen. As for nitrogen, although it is an important component of the atmosphere, it is not the most direct key to life activities.
Hydrogen and oxygen are both of the most powerful functions in life activities. Water, the source of life, is formed by the combination of hydrogen and oxygen. Everything in the world, whether animals or plants, depends on water for survival. Water is in the body of organisms, either as a solvent to assist in the transmission of nutrients; or as a medium, participating in various biochemical reactions. Without hydrogen and oxygen to make water, the birth and continuation of life would be empty talk.
Furthermore, oxygen plays a central role in respiration. Organisms breathe in oxygen and exhale carbon dioxide. Oxygen in the body, through complex biochemical processes, reacts with organic matter to release energy to support life activities, such as movement, growth, reproduction, etc. Without this process, various functions of life will be stagnant.
In addition, hydrogen is also a key player in many biochemical reactions. For example, photosynthesis, plants borrow light energy to decompose water and release hydrogen and oxygen. Hydrogen participates in subsequent reactions to assist in the formation of organic matter, providing a material basis and energy reserve for life.
Although nitrogen is the main component of the atmosphere, it is also a constituent element of proteins and nucleic acids in organisms. However, in organisms, it needs to undergo complex transformations, such as nitrogen fixation, before it can be used by organisms. Compared with the direct and immediate functions of hydrogen and oxygen in life activities, the role of nitrogen is slightly indirect.
Therefore, the direct importance of hydrogen and oxygen in life activities far exceeds that of nitrogen.

To prepare 3-bromo-2-pentene-4-alkynic acid, the following methods can be used:
First, the compound containing alkynyl group and carboxyl group is used as the starting material. The carboxylic acid containing alkynyl group and the suitable halogenated hydrocarbon undergo a nucleophilic substitution reaction in the presence of a base, and the halogen atom is introduced at the appropriate position of the alkynyl group. After the elimination reaction, the halogen atom is separated from the adjacent hydrogen atom to form a double bond. This process requires careful selection of reaction conditions to ensure that the alkynyl group and carboxyl group are not unduly affected. For example, using propionic acid and 1-bromo-2-chloroethane as raw materials, under the action of potassium carbonate and other bases, in a suitable organic solvent, the propionic acid derivative containing halogenated hydrocarbon groups is first obtained, and then the elimination reaction occurs under strong bases such as alcohol and potassium heating conditions. The partial structure of the target product can be obtained, and then subsequent modifications and adjustments can be made to meet the structural requirements of the target product.
Second, the reactivity of alkenyl compounds is utilized. Select alkenyl containing suitable substituents, first protect the carboxyl group to prevent it from participating in unnecessary reactions in the reaction, such as esterification reaction to convert the carboxyl group into an ester group. Then the alkynne part is brominated, and N-bromosuccinimide (NBS) and other brominating reagents can be selected. In the presence of light or initiator, the radical bromination reaction is carried out in a suitable solvent, and the bromine atom is introduced at the appropriate position of the alkynne. After that, the protected carboxyl group is deprotected to restore the carboxyl group to obtain the target product. For example, using 2-pentene-4-ethylene acetate as raw material, after bromination by NBS, hydrolysis under acidic or alkaline conditions removes the ethyl ester protecting group to obtain 3-bromo-2-pentene-4-alkynic acid.
Third, from the perspective of constructing carbon-carbon bonds. The coupling reaction of alkynes and halogenated olefins can be utilized. First, alkynes derivatives containing carboxylic groups and suitable halogenated olefins are prepared. In the presence of metal catalysts and ligands such as palladium and copper, the coupling reaction is carried out to construct compounds containing alkenyl structures. Subsequently, if bromine atoms need to be introduced, appropriate bromination methods can be selected according to the properties of the compound, such as electrophilic bromination or free radical bromination, and bromine atoms can be introduced at specific positions to obtain the target product. For example, carboxyl alkynes and 2-bromo-1-chloro-1-propylene are coupled under the action of Pd (PPh) and other catalysts and bases, and then the target product is synthesized after subsequent treatment.

I am looking at your question, and I am inquiring about the price range of hydrochloric acid, sulfuric acid, and nitric acid in the market. These three are all common and widely used chemical substances, but their prices are not static and often fluctuate due to many factors.
Let's talk about hydrochloric acid first, which is an aqueous solution of hydrogen chloride and is widely used in industrial fields, such as metal surface cleaning, chemical synthesis, etc. Generally speaking, industrial-grade hydrochloric acid, with a concentration of about 30% - 32%, has a market price of roughly 100-500 yuan per ton. However, if the purity is higher and reaches the reagent grade, the price will rise sharply due to strict requirements for impurities, and the price will rise sharply, reaching tens of yuan per liter.
As for sulfuric acid, it is an important chemical raw material and indispensable in fertilizer manufacturing, petroleum refining, metal smelting and many other industries. Common industrial concentrated sulfuric acid, with a concentration of 98%, costs about 200-800 yuan per ton. If it is a special grade, such as battery-specific sulfuric acid, the price may vary due to different quality requirements.
As for nitric acid, it has strong oxidizing properties and is often used in chemical, military and other fields. Ordinary industrial nitric acid, with a concentration of 65% - 68%, costs about 800-2000 yuan per ton. And high-purity fuming nitric acid, due to the complex preparation process, is more expensive.
It should be noted that these chemicals are corrosive and dangerous, and their trading, transportation and storage are subject to strict regulations and safety standards. Therefore, the actual transaction price may vary from the above price range due to factors such as regional differences, market supply and demand, transportation costs and related policies.