3-aminopyridine

3-Hydroxybutyric acid, its main uses are:
In the field of medicine, the sodium salt of 3-hydroxybutyric acid, sodium hydroxybutyrate, has certain applications in the field of anesthesia. It can be used as an intravenous general anesthesia drug, with the characteristics of fast onset, short action time, and stable recovery. During anesthesia induction, it can enable patients to quickly enter the anesthesia state, and has relatively little impact on the respiratory and circulatory systems. It is suitable for short surgeries and adjuvant drugs for compound anesthesia. Because of its low degree of interference with the patient's physiological functions, it helps to maintain the relative stability of the patient's vital signs during the operation.
However, it is necessary to be particularly vigilant that 3-hydroxybutyric acid is at high risk of being abused in non-medical settings It is often used by criminals as a new type of drug. Because it is colorless and odorless, it can be easily added to beverages and other items. After the victim ingests it unknowingly, he will experience temporary memory loss, nausea, vomiting and other symptoms, and even fall into a coma. At the same time, long-term abuse of 3-hydroxybutyric acid will cause serious damage to the human nervous system, cardiovascular system, etc., resulting in memory loss, cognitive dysfunction, arrhythmia and many other health problems, which seriously threaten the life and health of users.
In addition, due to its abuse in the field of drugs, it is strictly controlled. In our country, the private production, transportation, trafficking, and use of 3-hydroxybutyric acid are all illegal acts, aiming to severely crack down on its illegal circulation and protect public health and social order.

3-Hydroxybutyric acid, its physical properties are as follows:
This substance is a colorless to slightly yellow transparent viscous liquid at room temperature, with a weak smell and a special fruity aroma. The boiling point is quite high, about 207 to 208 degrees Celsius, which means that a higher temperature is required to transform it from liquid to gaseous. The melting point is relatively low, between -43 and -42 degrees Celsius, that is, the temperature is slightly higher than this range, and it will melt from solid to liquid.
Its density is similar to that of water, about 1.07g/cm ³, so when mixed with water, it will not be stratified rapidly due to excessive density differences. It has good solubility, can be miscible with water in any ratio, and can also be soluble in common organic solvents such as ethanol and ether. This is due to the polar groups such as hydroxyl and carboxyl groups contained in its molecular structure, which enhances its ability to interact with polar solvents.
In addition, the viscosity of 3-hydroxybutyric acid is moderate, and it exhibits a certain internal friction during the flow process. It is neither as easy to flow as water, nor too viscous and difficult to move. In appearance, pure 3-hydroxybutyric acid is transparent and uniform, with no impurities or suspended solids visible to the naked eye, and will show a clear texture under light exposure. These physical properties make it possible to apply in many fields, but at the same time, due to some special properties, it needs to be properly controlled and used in some occasions.

3-Hydroxybutyric acid, this physical property is unstable. Looking at its chemical properties, the hydroxyl group and the carboxyl group are combined in one body, the hydroxyl group has nucleophilic ability, and the carboxyl group is acidic. The coexistence of the two causes the reaction of esterification in the molecule, which endangers its own stability.
When the temperature rises, or there is a catalytic agent, the intramolecular hydroxyl group interacts with the carboxyl group in an easy phase, condensation and dehydration, and generates γ-butyrolactone. This process is spontaneous and irreversible, which shows that its physical properties are volatile and difficult to maintain their own state under heating conditions.
Furthermore, in the environment of acid and alkali, 3-hydroxybutyric acid is also difficult to tolerate. When encountering alkali, the carboxyl group is prone to proton loss and forms carboxylates, which changes the charge distribution and chemical activity of its molecules; when encountering acid, the hydroxyl group may be protonated, enhancing its nucleophilic activity, or triggering a different reaction, causing its structure and properties to change.
From the perspective of its storage, even under low temperature and dry conditions, due to the characteristics of its own chemical structure, it will gradually change over time, resulting in gradual changes in purity and physical properties. Therefore, the chemical properties of 3-hydroxybutyric acid are difficult to stabilize, and under the influence of various environmental factors, it is often easy to change its own state and properties.

3-Aminopyridine is an important intermediate in organic synthesis. There are many synthesis methods. The following are common ones:
1. ** Synthesis method using pyridine as raw material **:
- ** Direct amination method **: Pyridine can be reacted with amination reagents under specific conditions to directly generate 3-aminopyridine. This reaction often requires the use of metal catalysts, such as copper, palladium, etc. Taking copper catalysis as an example, pyridine reacts with an amino source at a certain temperature in the presence of appropriate ligands, bases and solvents. The reaction mechanism is that the copper catalyst first forms an active intermediate with the amino source and ligand, and then undergoes a nucleophilic substitution reaction with pyridine to obtain 3-aminopyridine. The advantages of this method are that the steps are simple and the atomic economy is high; the disadvantages are that the reaction conditions are more harsh, the catalyst requirements are strict, and the selectivity is sometimes poor.
- ** Indirect amination method **: Pyridine is functionalized first, a group that can be converted into an amino group is introduced, and then converted into an amino group through further reaction. For example, pyridine first reacts with halogenated reagents to generate 3-halogenated pyridine, and then 3-halogenated pyridine reacts with ammonia or amine compounds under the action of catalysts to obtain 3-aminopyridine. In this process, the halogenation reaction conditions are relatively mild, easy to control, and the selectivity of nucleophilic substitution reaction is better. However, the disadvantage is that the reaction steps are increased, and the total yield may be affected.
2. ** Synthesis method using nitrogen-containing heterocyclic compounds as raw materials **:
- ** Using nicotinamide as raw material **: Nicotinamide can be converted into 3-aminopyridine after Hoffman degradation reaction. Under basic conditions, nicotinamide reacts with halogens such as bromine or chlorine to form isocyanate intermediates, which are hydrolyzed to obtain 3-aminopyridine. The raw materials of this method are relatively easy to obtain, the reaction conditions are relatively mild, and the yield is acceptable. However, the Hoffmann degradation reaction will produce a large amount of halogen-containing waste, which is not friendly to the environment.
- ** Using other nitrogen-containing heterocycles as raw materials **: Some nitrogen-containing heterocyclic compounds with similar structures to pyridine can also be synthesized with appropriate modification and transformation. For example, specific quinoline derivatives can be synthesized by selective ring opening and subsequent amination reactions. This kind of method requires careful design of the reaction route according to the structure of the starting material, which is more flexible, but also more difficult to synthesize.
3. ** Synthesis method using acyclic compounds as raw materials **:
- ** Using 1,5-dicarbonyl compounds and ammonia as raw materials **: 1,5-dicarbonyl compounds and ammonia undergo intramolecular cyclization reaction, which can build a pyridine ring, and then introduce amino groups to obtain 3-aminopyridine. This reaction is usually carried out under acid or base catalysis. By ingeniously designing the structure of 1,5-dicarbonyl compounds, 3-aminopyridine can be synthesized. This method has a wide range of raw materials, a relatively green reaction process, and high atomic utilization. However, the control of reaction conditions requires strict regulation of cyclization and amination steps.

3-Hydroxybutyric acid should be kept in mind during storage and transportation.
It is a controlled psychotropic drug, and it must be stored and transported in a legal and compliant channel in strict accordance with regulatory requirements. When storing, it should be stored in a dry, cool and well-ventilated place, away from fire and heat sources, to prevent it from deteriorating or causing danger due to excessive temperature. At the same time, it needs to be stored separately from oxidants, acids and alkalis, and must not be mixed to avoid chemical reactions. The storage area should be equipped with corresponding varieties and quantities of fire-fighting equipment and leakage emergency treatment equipment to deal with emergencies.
When transporting, it is necessary to ensure that the packaging is complete and sealed to prevent leakage. Transport vehicles should have good ventilation equipment and travel according to the specified route to avoid densely populated areas and traffic congestion sections. Transport personnel also need to be professionally trained to be familiar with the characteristics of 3-hydroxybutyric acid and emergency treatment methods. During transportation, close attention should be paid to the status of the goods. If there is any abnormality such as leakage, corresponding measures should be taken immediately to avoid the expansion of harm.
In addition, whether it is storage or transportation, detailed records must be made, covering the time of entry and exit, quantity, transportation route and other information for traceability and inspection. Do not take chances and violate relevant regulations, otherwise you will face serious legal consequences. Only with caution can we ensure the safety of 3-hydroxybutyric acid during storage and transportation.