4-pyridinecarboxylic acid, 3-bromo-, ethyl ester

Sodium borohydride is a strong reducing agent, which is widely used in the field of organic synthesis and plays a key role in many reactions. Its chemical properties are as follows:
1. ** Reductivity **: Sodium borohydride can reduce many carbonyl-containing compounds, such as aldars and ketones, to corresponding alcohols. This reaction condition is usually relatively mild. For example, in ethanol or methanol solvents, aldars or ketones react with sodium borohydride, aldars can be efficiently converted into primary alcohols, and ketones are converted into secondary alcohols. The reaction principle is that the hydrogen anion (H) in sodium borohydride undergoes nucleophilic addition to the carbonyl carbon atom, and then hydrolyzes to obtain the alcohol product.
2. ** Reaction with water **: Sodium borohydride reacts slowly with water and releases hydrogen gas. The reaction equation is: $NaBH_ {4} + 2H_ {2} O = NaBO_ {2} + 4H_ {2}\ uparrow $. In view of this property, sodium borohydride needs to be properly stored and used in a dry environment, otherwise it will reduce its activity due to the reaction with water, affecting its reducing performance.
3. ** Selectivity **: Compared with lithium aluminum hydride, sodium borohydride has relatively weak reductivity, but it has a certain selectivity. It generally preferentially reduces carbonyl groups such as aldehyde and ketone, but has little effect on groups that are relatively difficult to reduce, such as ester groups, carboxyl groups, and cyanyl groups. For example, in the synthesis of some complex organic compounds, if there are both aldehyde and ester groups in the molecule, sodium borohydride can preferentially reduce the aldehyde group to alcohol, while the ester group can be retained, thus realizing the synthesis of organic compounds with specific structures.
Sodium borohydride, with its unique chemical properties, plays an indispensable role in the fields of organic synthesis, drug development, fine chemistry, etc., providing important methods and means for the preparation of many organic compounds.

"Tiangong Kaiwu" has written that mirabilite, its main component is sodium sulfate ($Na_ {2} SO_ {4} $), which is mostly derived from saline-alkali land or brine containing sodium sulfate, and obtained through processing. Its main uses are quite extensive, and are described as follows:
First, in the field of medicine, mirabilite has the functions of diarrhea and accumulation, moisturizing dryness and firmness, clearing heat and reducing swelling. It can be used to treat the stagnation of real heat, dry stool, and often combined with rhubarb to increase the power of laxative under diarrhea. Apply externally to the swelling of sores, it can clear away heat and reduce swelling, and dissipate carbuncle swelling and sores.
Second, in industrial production, mirabilite has various uses. In the glass manufacturing industry, mirabilite, as a flux, can reduce the melting point of glass raw materials, make glass raw materials easier to melt, improve glass production efficiency, and optimize the quality and performance of glass, such as enhancing the transparency and hardness of glass. In the paper industry, mirabilite can participate in the pulping process, help the separation and cooking of fibers, and improve the quality of pulp. In the printing and dyeing industry, mirabilite can be used as a dye enhancer to speed up the dyeing of fibers on dyes, improve the utilization rate of dyes, and make dyeing more uniform and firm.
Third, mirabilite is also found in the agricultural field. Appropriate application of mirabilite can adjust soil pH and improve soil structure, especially for alkaline soil. In addition, the sulfur and sodium elements contained in mirabilite are nutrients required for plant growth, which can promote plant metabolism, enhance plant stress resistance, and improve crop yield and quality.
To sum up, mirabilite plays an important role in many fields such as medicine, industry, agriculture, etc., and is of great significance to the national economy and people's livelihood.

To prepare ethyl 3-hydroxy-4-pentenoate, there are many ways to synthesize it.
First, it can be started from a suitable enolide. Nucleophilic substitution reaction is carried out between enolide and halogenated ethyl acetate. In this process, the carboanion of the enolide attacks the carbonyl α-carbon of halogenated ethyl acetate, and the halogen ions leave to form a carbon-carbon bond to build a preliminary carbon skeleton. Subsequently, appropriate oxidation reactions are performed on the obtained products, and the degree of oxidation is precisely adjusted to introduce hydroxyl groups at suitable positions, and finally the synthesis of ethyl 3-hydroxy-4-pentenoate is achieved.
Second, the condensation reaction of aldol and ketone can be used. Select suitable aldol and ketone, and under the action of basic catalyst, the condensation reaction of hydroxyaldehyde occurs. The carbonyl group of the aldehyde and the α-hydrogen of the ketone are catalyzed by alkali to form enol negative ions, and then the nucleophilic addition of the carbonyl group of the aldehyde is launched to generate β-hydroxyaldehyde or ketone intermediates. Next, the intermediate is dehydrated to form a carbon-carbon double bond, and then the carbonyl group is esterified, and the alcohol and acid are esterified under the action of the catalyst to obtain the target product 3-hydroxy- 4-pentenoic acid ethyl ester.
Third, it can also pass the reaction of Grignard reagent. First prepare the Grignard reagent containing alkenyl groups, and make it perform addition reaction with carbonyl compounds (such as esters or alters). The carbon-magnesium bond of Grignard reagent has strong nucleophilicity and attacks the carbon atom of the carbonyl group to form a new carbon-carbon bond. Subsequent steps such as hydrolysis, the magnesium-halogen bond is converted into hydroxyl groups, and then esterification is carried out to realize the synthesis of 3-hydroxy- 4-pentenoate ethyl ester.
All kinds of synthesis methods have their own advantages and disadvantages. According to the actual situation, such as the availability of raw materials, the conditions of reaction, and the purity requirements of the product, etc., we need to weigh carefully and choose the advantages and use them to efficiently synthesize ethyl 3-hydroxy- 4-pentenoate.

Mercury tetraethyl is required for storage and storage processes, and all materials need to be careful. If there is a slight mismatch, there will be a problem. The following information should be paid attention to.
Mercury, the common water, is often in the presence of liquid gold. When it is stored, a sealed container must be used to prevent it. Because it is toxic to steam, if it is in the air, it will be harmful to the mental system, digestive system, etc. The container also needs to be resistant to corrosion. Mercury can react to various substances. If the container is rotten, the risk of leakage will be greatly increased. And the storage environment should be suitable, and the source of fire and pollution should be used. If the degree increases, the mercury will accelerate.
Mercury, the packaging must be well-qualified. It is commonly used to fix gold barrels or glass bottles, and fill them with inert materials to prevent shock. It also needs to be used to prevent leakage, pass through and so on. It is necessary to protect people from pollution, familiar with the harm of mercury and emergency disposal methods. On the way, make sure to check the package. If there is any leakage, quickly evacuate the crowd, seal the package, and collect and clean it by the method.
tetraethyl, there are gold compounds, which are highly toxic. It needs to be sealed, dry, and well-cleared to avoid oxidation, acid, etc. Because of its chemical activity, it is easy to react to many substances. And it is necessary to isolate food, materials, etc., to prevent pollution.
tetraethyl, the package can withstand a certain force, shock, and prevent leakage. Tools should be cleaned and disinfected, and other items should not be destroyed. If there is any problem, please stop immediately. Once it leaks, quickly isolate it and cut off the ignition source, because tetraethyl is flammable. Rescuers should wear anti-burning utensils and use sand, vermiculite and other adsorption, and cannot directly connect it.

Today I have a question, what is the market price of borax and ethyl borate?
Borax is a common inorganic compound with a wide range of uses and is used in glass, ceramics, metallurgy and other industries. Its market price often varies due to quality, origin, supply and demand conditions and many other factors. At present, the price of ordinary industrial grade borax is about 3,000 to 5,000 yuan per ton. If it is high-purity, special grade borax, the price may be higher, up to 7,000 to 8,000 yuan per ton, or even more than 10,000 yuan.
Ethyl borate is an organic borate ester compound, which is commonly used in organic synthesis, medicine and chemical industry. Its market price is also affected by factors such as raw material cost, production process, and market demand. Generally speaking, the price of industrial ethyl borate per kilogram is about 80 yuan to 150 yuan. The price of laboratory-grade, high-purity ethyl borate can reach hundreds of yuan per kilogram.
It should be noted that these prices are only rough estimates, and the market conditions are changing rapidly. To obtain accurate prices, please consult relevant manufacturers and distributors for details, or refer to real-time quotations from professional industry information platforms.