4-mercaptopyridine

The main uses of 4-alkynylbenzene are related to many fields. From the perspective of "Tiangong Kaiwu", although this substance was not directly described at that time, it can be used in today's chemical process knowledge.
In the field of organic synthesis, 4-alkynylbenzene is a key intermediate. For example, in pharmaceutical chemistry, the active reactivity of its alkynyl groups can be used to construct complex drug molecular structures. Analogous to the ancient process, just like the clever compatibility of various alchemy stones in traditional alchemy, today, 4-alkynylbenzene is combined with other organic reagents by scientific methods to make drugs with specific pharmacological activities to treat various diseases.
In materials science, 4-alkynylbenzene can participate in the synthesis of polymers. For example, the preparation of special polymer materials endows the material with unique electrical and optical properties. Just like the skilled craftsmen of ancient times who treated the material with unique techniques to make it extraordinary. This material may be used in electronic devices, such as the manufacture of high-performance display screens, and its photoelectric conversion performance may be optimized by the introduction of 4-alkynylbenzene, resulting in clearer and more vivid images.
In supramolecular chemistry, 4-alkynylbenzene can build an ordered supramolecular structure through the special interaction between alkynyl groups and other groups. It is like building a building in ancient times, using the delicate combination of mortise and tenon to build a grand and stable structure. Such supramolecular structures may be used in molecular recognition, catalysis and other fields to provide efficient and accurate assistance for chemical processes.
In addition, 4-alkynylbenzene can also be used in the preparation of new catalysts. It can be modified on the surface of the catalyst support to change the active check point structure and performance of the catalyst, and improve catalytic efficiency and selectivity. Just like the ancient craftsmen sharpened tools to make them sharp and accurate, this optimizes the chemical reaction path, reduces energy consumption, and increases yield, which is of great significance in chemical production.

The physical properties of 4-alkynylbenzene are as follows:
This substance is mostly solid at room temperature, due to relatively strong intermolecular forces. The appearance is often white or off-white crystalline powder, and the texture is more delicate.
In terms of melting point, the melting point of alkynylbenzene is relatively high. This is because the presence of alkynyl groups enhances the interaction between molecules, so that the molecules need to absorb more energy to overcome the lattice energy, so as to realize the transition from solid to liquid.
The boiling point is also higher. In addition to van der Waals force, the intermolecular forces may be generated by the alkynyl groups, which increases the intermolecular forces and the energy required for gasification.
In terms of solubility, 4-alkynylbenzene is difficult to dissolve in water. Water is a polar molecule, and in the molecular structure of 4-alkynylbenzene, the benzene ring and the alkynyl group are dominated by the non-polar part. According to the principle of similarity dissolution, it is difficult to form an effective interaction with water molecules, so it is difficult to dissolve in water. However, it is soluble in common organic solvents, such as dichloromethane, chloroform, tetrahydrofuran, etc. The non-polar or weakly polar characteristics of these organic solvents match that of 4-alkynylbenzene, and the molecules can dissolve each other through van der Waals forces.
The density is slightly larger than that of water, its molecular structure is compact, and the relative mass distribution of atoms is concentrated, resulting in a larger mass per unit volume, so the density is higher than that of water. When storing, in view of its physical properties, it should be sealed and stored in a cool, dry place to avoid light and high temperature, in order to prevent its physical state from changing or deteriorating due to factors such as temperature, humidity and light.

4-Hydroxypyridine is an organic compound whose molecules contain hydroxyl groups and pyridine rings. Although this substance is not detailed in "Tiangong Kaiwu", its chemical properties can be deduced from ancient chemical knowledge.
4-Hydroxypyridine is weakly acidic, because its hydroxyl groups can slightly ionize hydrogen ions. The ancients said: "4-Hydroxypyridine, containing hydroxyl groups, can be acidic. Although it is slight, it also has the quality of acid. In water, it can be less separated from hydrogen ions, showing the sign of acid."
Its hydroxyl groups can react with active metals such as sodium to form corresponding salts and hydrogen gas. The ancients may remember: "When sodium encounters 4-hydroxypyridine, it can be seen that sodium is active and sluggish. Gas is hydrogen, and the adult is a salt. Due to the activity of the hydroxyl group, it is easy to react with sodium. "
The pyridine ring of 4-hydroxypyridine is aromatic, relatively stable, and can undergo electrophilic substitution. The ancients or said:" The pyridine ring is like the genus of aromatic rings, which is stable and electrophilic. In case of electrophilic agents, it can be substituted, such as halogenation, nitrification, etc. With the electron cloud distribution of its ring, the electrophilic group is easy to enter a specific position. "
Hydroxy groups can participate in esterification reactions and form esters with acids under the action of catalysts. The ancients or said:" The hydroxyl groups of 4-hydroxypyridine, which are co-located with acids and catalyzed by catalysts, can form esters. This reaction is similar to the ordinary esterification method, where the hydroxyl group is condensed with the carboxyl group in the acid, and the water is removed to form an ester. "
4-Hydroxypyridine has hydroxyl groups and pyridine rings, or can form intramolecular or intermolecular hydrogen bonds, which affects its physical and chemical properties. The ancients or observe:" This substance may have the shape of a hydrogen bond because of the hydroxyl group and the pyridine ring. The hydrogen bond within or between molecules can change its melting point and solubility. "
Although" Tiangong Kaiwu "does not involve 4-hydroxypyridine, according to ancient chemical principles and experience, its chemical properties can be deduced in this way.

First, choose the material to be the most heavy. The material of the crossbow body should be tough wood, such as zhe wood, sandalwood and the like. This kind of good wood has a tight texture and a straight texture, which can lay a solid foundation for the crossbow body. Its rigidity and flexibility go hand in hand. When stressed, it can not only withstand the pull of the string, but also is not easy to break and crack, just like beams and pillars in a vast building, which is very important.
Second, the crossbow arm must be carefully crafted. The craftsman uses ingenuity and skills to shape the crossbow arm according to the shape of the human body. Make the crossbow holder comfortable to hold and force naturally. The width and curvature of the crossbow arm have been carefully considered to fit the wonders of man-machine. And on the crossbow arm, or engraved with patterns, it not only enhances the appearance, but also has the effect of anti-skid.
Third, the selection and production of strings should not be underestimated. Use beef tendons, silk threads and other tough things. First soak the beef tendons in a special concoction to remove its oil and increase its toughness. Then it is twisted with silk threads and wrapped layer by layer to make the strings tough and elastic. Strings are like the blood of a crossbow, the blood is smooth and powerful, and the crossbow can shoot far.
Fourth, the creation of the crossbow machine is about precision and durability. Using bronze or fine iron as material, it goes through multiple processes such as casting, grinding, and debugging. The components must be tightly fitted and the tolerance is extremely small. Teeth, cantilever knives, and lookout mountains and other components must be carefully crafted. The lookout mountain is used for aiming, and whether its scale is accurate or not is directly related to the hit of the arrow; the teeth and cantilever knives must be sensitive and reliable to control the launch, so that the arrow can be shot out in an instant.
Fifth, the adjustment method is also the key. After the crossbow is completed, repeatedly test fire, according to the landing point of the arrow, adjust the curvature of the crossbow arm and the angle of the crossbow machine. Or increase or reduce the weight to make the center of gravity of the crossbow suitable. Only by adjusting it many times can you get a good crossbow, and the arrow will hit, and the power is considerable. < Br >
All these are the key to making crossbows. Craftsmen use ingenuity and skills to integrate into the manufacture of crossbows, making crossbows a weapon to defeat the enemy on the battlefield.

Those who want to make good use of the crossbow machine should know the importance of all things. The crossbow machine is exquisite and a sharp weapon of battle. When it is used, there are many matters that need to be paid attention to.
The first one is to observe the shape of the crossbow machine. Before using it, it is necessary to examine its parts carefully, depending on whether the bow body is damaged or deformed, and whether the string is tough and unbroken. If the bow body is flawed, or the string is loose, it can cause the launch to be inaccurate and the power is greatly reduced. For example, the "Kaogong Ji" says: "The bow is a bow, and the six materials must be used when it is taken. The six materials are gathered, and the clever ones are combined with it." This is the weight of the bow body material and production. When using a crossbow, it is also necessary to always check its quality to ensure its integrity.
Second, learn the method of launching. When launching a crossbow machine, the force needs to be equal, and the aim should be accurate. The crossbow operator should practice regularly, and be familiar with changes in strength and angle. When launching, the mind should be calm, the qi should be stable, and it should not be panicked. If the enemy is in a battle, the enemy is aggressive, if the crossbow operator is impatient, it will be difficult to hit. The ancient good shooters have all undergone months and years of practice before they can pierce the Yang Dynasty. The same is true for the crossbow machine.
Furthermore, the limit of the bright crossbow machine. Although the crossbow machine is advantageous, its range and rate of fire are fixed. When using a crossbow, it should not be forced. If the enemy is too far away, beyond the range of the crossbow, it will be futile to fire, consuming arrows and revealing their whereabouts. When you know the suitable environment of the crossbow machine and judge the situation, you can get its benefits.
There are also, take good care of the crossbow machine. After use, it should be properly placed to avoid moisture and rust. If you leave it alone for a long time, the machine parts will be easily damaged, and eventually the crossbow machine will be damaged. "Tiangong Kaiwu" says: "Where you use an iron tool, take the iron that has been fried and cooked. First cast the iron into an anvil, thinking that the place where it is hammered." Equipment needs maintenance, and the crossbow machine is no exception.
Where you use a crossbow machine, check its condition, learn its laws, understand its limitations, and protect its body, all these things are prepared, so that you can make good use of the crossbow machine, so that it can be in the battle, and play the ability to defeat the enemy.