The things that the observer inquired about, 1. "Mercury", 3. (mercury methyl), 5. Bromobenzene, etc., are all chemical properties, each with its own characteristics.
Mercury, commonly known as mercury, is the only metal that is liquid at room temperature. It is silver-white and has a metallic luster. Its density is quite high, its fluidity is good, and it is volatile, and its vapor is highly toxic. Mercury's chemical properties are relatively stable. It does not interact with oxygen at room temperature, and when heated, it combines with oxidation to form mercury oxide. In case of sulfur powder, the two combine rapidly, and this property is often used to remove mercury.
As for "mercury methyl", this refers to methyl mercury, which is an organic mercury compound. It is highly lipid-soluble, highly toxic, easy to accumulate in organisms, passed through the food chain, and is extremely harmful.
Bromobenzene, a colorless oily liquid, has a special odor, insoluble in water, and has a density greater than that of water. Its chemical properties are relatively stable. Due to the conjugation effect of the benzene ring, the activity of bromine atoms is suppressed, and it is more difficult to replace than halogenated alkanes. However, under specific conditions, such as the presence of catalysts, reactions such as nucleophilic substitution can occur.
All kinds of substances, each with wonderful chemical properties, are used in chemical industry, scientific research and other fields, or for assistance, or need to be treated with caution to prevent harm.

Mercury, (mercury methyl), pentaborane, etc. are all highly toxic or chemical substances with special properties, and their main uses are particularly critical and different.
Mercury was often used in alchemy in ancient times, and alchemists believed that it could refine elixirs of immortality. This is because of the unique chemical properties of mercury, which seems to cause wonderful changes in the process of alchemy. In the medical field, it was also used in the past, such as mercury as a medicine, but now it is rarely used because it is known that its toxicity is very high. In industry, mercury is often used in the manufacture of thermometers. Due to the extremely stable and obvious thermal expansion and contraction characteristics of mercury, it can accurately measure temperature changes. It is also used in some electrical switches, with its good conductivity and special physical properties, to ensure the opening and closing of circuits.
(mercury methyl), mostly from the methylation of mercury by microorganisms. This substance is particularly toxic and has a far-reaching impact in the environmental field. Because it is fat-soluble, it is easily enriched in organisms, transmitted along the food chain and amplified step by step, seriously threatening the ecosystem and human health, and has no positive use. It is mainly used to study its environmental behavior and hazard prevention and control.
Pentaborane, in the aerospace field, was once regarded as a high-energy fuel with great potential. Because of its high combustion calorific value, it can provide powerful power for spacecraft to break through the attractive force of the earth and soar in the vast universe. In material science research, pentaborane also has certain applications. It can be used as a raw material for the preparation of special boride materials. With its unique chemical structure, it gives materials special physical and chemical properties, such as high strength and high temperature resistance, and promotes the development of materials science. However, it should be noted that pentaborane is extremely toxic and extremely unstable, and extremely strict safety measures need to be taken during use.

To prepare 1-alkyne-3- (alkynyl methyl) -5-bromopyridine, the following ancient method can be used.
First, start with a suitable halogenated pyridine, and make it meet with the alkyne-based fund reagent in a suitable reaction environment. When preparing the alkyne-based fund reagents, such as alkynyl lithium or alkynyl magnesium reagents, it is necessary to follow strict operation and control the reaction conditions, so that the metal and alkyne can be properly combined to obtain a reagent with good activity. This reagent and halogenated pyridine are placed in a suitable solvent, such as anhydrous tetrahydrofuran, and slowly react at a low temperature and protected by an inert gas. Due to the relative activity of the halogen atom in the halogenated pyridine, when encountering the alkyne-based reagent, the halogen atom leaves, and the alkynyl group is replaced to obtain the pyridine derivative containing the alkynyl group.
Then, 3- (alkynyl methyl) is introduced into the product. The alkyne can first interact with the halogenated methyl reagent, and the halogenated methyl reagent should be selected with moderate activity, such as bromomethyl halides. With the help of bases, the terminal hydrogen of alkynes is taken away to form alkynyl negative ions. Its nucleophilicity is very strong, and it can attack the carbon of the halogenated methyl and form a carbon-carbon bond, thus introducing the alkynyl methyl into the molecule. The choice of base is also critical. Commonly used ones such as potassium carbonate and potassium tert-butyl alcohol are carefully selected according to the reaction process and substrate characteristics.
As for the introduction of 5-bromine, after the above two steps are completed, depending on the activity and stability of the molecule as a whole, choose the appropriate brominating reagent. For example, N-bromosuccinimide (NBS), often benzoyl peroxide is used as the initiator, under light or heating conditions, the bromine atom selectively replaces the hydrogen at the 5-position of pyridine. During the reaction, close attention should be paid to the temperature, reagent dosage and reaction time to prevent the generation of polybrominated products.
After each step of the reaction, the product needs to be carefully purified by recrystallization, column chromatography, etc., to ensure that the reaction follows the expected path and obtains high-purity 1-alkynne-3- (alkynyl methyl) -5-bromopyridine. Although this method follows the ancient method, the details are all about success and failure, and caution is required.

Mercury, (mercury methyl), pentaborane and other substances are related to human life and property and nature during storage and transportation, so extreme caution is required. The following precautions must be kept in mind.
Mercury is a liquid metal at room temperature, which is highly volatile and highly toxic. When storing, it should be placed in a sealed container to prevent mercury vapor from escaping into the atmosphere, causing environmental pollution and human poisoning. Containers should be solid and leak-proof, often made of thick-walled glass or metal. And should be stored in a low temperature, cool and well-ventilated place, away from fire and heat sources. Due to the increase in temperature, the volatility of mercury will increase sharply. When transporting mercury, the packaging must be stable. Most of them are loaded in special mercury transportation bottles, and the outside of the bottles is wrapped with shockproof and anti-collision materials. The whole process of transportation must be closely monitored to ensure that there is no risk of leakage.
Mercury-containing methyl substances are more toxic than mercury, and are chemically active. When storing such substances, in addition to the conventional requirements such as sealing, low temperature, shade and good ventilation, it is also necessary to consider their special impact on the material of the storage container. Because it may chemically react with some materials, it is necessary to choose a container that is compatible with it. During the transportation process, not only the packaging should be stable and leak-proof, but also the transportation environment should be strictly controlled to avoid packaging damage caused by vibration and collision. At the same time, transportation personnel need to be professionally trained and familiar with the characteristics of such substances and emergency treatment methods.
Pentaborane is a highly toxic and highly spontaneous combustible substance. The storage of pentaborane must be in an absolutely anhydrous and oxygen-free environment, mostly protected by inert gas. The container must be pressure-resistant, sealed, and equipped with explosion-proof devices. Because it is highly prone to spontaneous combustion and explosion in contact with water and air, the storage place should be equipped with strict fire protection and explosion-proof facilities, and fireworks are strictly prohibited. When transporting pentaborane, the vehicles used must be specially made, with good heat insulation, fire protection and explosion-proof performance. During transportation, temperature, pressure and other parameters should be monitored in real time to ensure transportation safety. In the event of a leak, the surrounding personnel must be evacuated immediately and must not be approached. At the same time, report to the professional emergency team for handling.

Mercury, (mercury methyl), and pentaborane are of great significance to the environment and human health.
Mercury is a highly toxic metal element. It is released in the natural environment, or through volcanic eruptions, rock weathering, etc. However, human activities, such as mining and burning of fossil fuels, also cause large amounts of mercury to enter the environment. Mercury is highly volatile and can be transported over long distances in the atmosphere. Once deposited in water, it can be converted into methylmercury through microbial action. Methylmercury is highly fat-soluble, easy to accumulate in organisms, and accumulates along the food chain. If humans eat aquatic organisms containing methylmercury, mercury toxicity can easily damage the human brain, immune system, and cardiovascular system. In mild cases, there may be dizziness, fatigue, and insomnia; in severe cases, it can cause limb tremors, language impairment, vision loss, and even life-threatening.
(mercury methyl), that is, methylmercury, has previously described its enrichment in the environment and the mechanism of human toxicity. It is particularly harmful to pregnant women and fetuses. It can be transmitted to the fetus through the placenta, damaging the development of the fetal nervous system, causing mental retardation, developmental retardation and other congenital diseases.
Pentaborane is a highly toxic and highly irritating chemical. In the environment, if it leaks, it can cause air, soil, and water pollution. If people inhale pentaborane, it can seriously irritate the respiratory tract, causing cough, asthma, breathing difficulties, and even pulmonary edema. If it comes into contact with the skin, it can cause burns and allergies. Long-term exposure may damage the function of organs such as liver and kidney, causing abnormal biochemical indicators and affecting the normal metabolism of the human body.
Therefore, mercury, (mercury methyl), pentaborane, etc. pose a huge threat to the environmental ecological balance and human health. The top priority is to strengthen monitoring and strictly control related production activities to reduce their release to the environment and protect the natural environment and human well-being.