3-Hydroxy-4-methoxybenzoic acid, although this substance is not directly recorded in ancient books, it can be compared to ancient medicines based on current pharmacology and application. Its functions are covered by the following numbers.
First, it is related to medical treatment. In terms of today's research, it has certain anti-inflammatory properties. Ancient healers, treating inflammatory diseases, often used drugs to clear away heat and purge fire, cool blood and detoxify. Although this 3-hydroxy-4-methoxybenzoic acid has no ancient books, it has anti-inflammatory properties, or can be used to relieve heat syndrome and inflammation in the body, such as honeysuckle and forsythia in ancient recipes. And it may have the power to regulate the immune system, just like the ancient astragalus, which can help correct and remove evil spirits, make the human body full of positive energy, and resist the invasion of external evil spirits.
Second, in the way of health care and skin care. Today's research shows that it may have antioxidant effects. Ancient dignitaries, seeking ways to stay in the face, often use pearl powder, ginseng and other substances. This 3-hydroxy-4-methoxybenzoic acid, with its antioxidant properties, may delay the aging of the skin. For example, Angelica dahurica used in ancient recipes, can whiten the skin, reduce wrinkles, and make the skin smooth and delicate.
Third, in the field of food preservation. Today it is known that it has certain antibacterial properties. In ancient cooking, in order to keep food alive for a long time, it was often salted and air-dried. If 3-hydroxy-4-methoxybenzoic acid is used, it can be analogous to the antiseptic method of spices in ancient times, such as prickly ash, star anise, etc., to prevent food from spoiling and prolong the shelf life of food.
Fourth, in chemical products. Although ancient books did not involve chemical industry, in today's view, it may be used to prepare special chemical materials. This may be similar to the ancient alchemists who used various ores to refine medicinal pills. Although the purpose is different, they are all for the transformation and application of substances. Its potential value in the chemical industry may lead to the development of unique materials for textile, coating and other industries.

3-Hydroxy-4-methoxybenzoic acid is a very important organic compound. Its physical properties are as follows:
Looking at its properties, this substance is mostly white to light yellow crystalline powder under normal conditions, with fine texture and a regular shape when viewed with the naked eye. This form has certain effects in many chemical reactions and practical applications. Its crystalline properties are conducive to separation and purification. In the chemical production process, high purity of this substance can be obtained by crystallization.
When it comes to melting point, the melting point of 3-hydroxy- 4-methoxybenzoic acid is about 110 ° C - 112 ° C. Melting point is an inherent physical property of a substance, and this value is extremely critical. In laboratory operations and industrial production, the determination of melting point is often used as an important indicator to identify the purity of the substance. If the purity of the substance is very high, the melting point value will be very close to the theoretical value; if it contains impurities, the melting point will be reduced and the melting range will be lengthened.
In addition to solubility, the substance is slightly soluble in water. This property indicates that the interaction force between it and water molecules is weak. However, it is soluble in organic solvents such as ethanol and ether. This solubility characteristic is widely used in the field of organic synthesis. During the reaction process, a suitable solvent can be selected according to this characteristic to promote the smooth progress of the reaction. For example, in some occasions where a homogeneous reaction environment is required, an organic solvent that can dissolve the substance can be selected to make the reactants fully contact and improve the reaction efficiency. At the same time, in the separation and extraction of substances, it can also take advantage of their solubility differences to achieve effective separation from other substances.

3-Benzyl-4-chlorophenylacetic acid is an organic compound with unique chemical properties. This substance contains benzyl and chlorophenylacetyl groups, which have a great influence on its chemical behavior.
From the perspective of reactivity, the benzyl ring in benzyl has a large π bond and a high electron cloud density, so it has a certain nucleophilicity. In chlorophenylacetyl, the chlorine atom has strong electronegativity, which reduces the electron cloud density of the benzene ring, and the α-carbon is affected by the carbonyl group and the chlorine atom, which has a certain positive electricity. This makes 3-benzyl-4-chlorophenylacetic acid easily react with nucleophiles, such as alcohols, amines, etc. Under suitable conditions, substitution reactions can occur to generate corresponding esters or amides.
In terms of acidity, due to the presence of carboxyl groups, 3-benzyl-4-chlorophenylacetic acid is acidic. The electron-absorbing induction effect of chlorine atoms can make carboxyl negative ions more stable, so its acidity is slightly stronger than that of phenylacetic acid. In an alkaline environment, carboxyl groups easily react with bases to form salts, which have good water solubility. This property can be used in the separation and purification of this compound.
In addition, the benzene ring in 3-benzyl-4-chlorophenylacetic acid can undergo typical aromatic reactions, such as halogenation, nitration, sulfonation, etc. The α-hydrogen of benzyl group has certain activity and can be halogenated under appropriate conditions.
3-benzyl-4-chlorophenylacetic acid has rich chemical properties, which lay the foundation for its application in organic synthesis, pharmaceutical chemistry and other fields.

The synthesis method of 3-benzyl-4-chlorophenylacetic acid is not described in detail in books such as Tiangongkai, but according to today's organic synthesis method, many paths can be deduced.
First, starting with chlorobenzene, through Fu-g alkylation reaction, benzyl is introduced into the counterposition of chlorobenzene to obtain 4-benzyl chlorobenzene. This step requires selecting a suitable catalyst, such as anhydrous aluminum trichloride, and reacting in a suitable temperature and solvent environment. Then, the nucleophilic substitution reaction of 4-benzyl chlorobenzene with monochloroacetic acid occurs under alkaline conditions. Commonly used bases include potassium carbonate, etc. In suitable organic solvents such as N, N-dimethylformamide (DMF), the reaction can be carried out in the direction of generating 3-benzyl-4-chlorophenylacetic acid.
Second, benzyl chloride and p-chlorophenylacetic acid can also be used as raw materials. First, p-chlorophenylacetic acid is made into a corresponding carboxylate, such as sodium salt, which can be reached by reacting with sodium hydroxide. Then, benzyl chloride and sodium p-chlorophenylacetate undergo nucleophilic substitution reaction. This reaction also requires control of temperature, solvent and other conditions. Commonly used solvents such as ethanol and acetone can obtain the target product 3-benzyl-4-chlorophenylacetic acid through this reaction.
In addition, other routes can be designed. For example, the intermediate containing benzyl and chlorobenzene is first constructed, and then the carboxyl group is introduced through carboxylation reaction. The method of Grignard reagent can be used to make phenyl magnesium chloride from chlorobenzene, react with benzyl halide to obtain the structure containing benzyl and chlorobenzene, and then react with carbon dioxide to generate 3-benzyl-4-chlorophenylacetic acid after hydrolysis. In this process, the preparation of Grignard reagent requires an anhydrous and oxygen-free environment, and the reaction conditions are relatively harsh, which requires fine regulation.
Although the above methods are difficult to trace in ancient books, with today's knowledge of chemical synthesis, multiple paths can be explored to synthesize 3-benzyl-4-chlorophenylacetic acid.

In today's market, the price of 3-hydroxy-4-methoxybenzoic acid often changes due to various reasons. This drug is widely used in medicine and chemical industry, so its price is also valued by everyone.
In the past market conditions, its price often varies according to quality, supply and demand. If the quality is high and less than the supply and demand, the price may increase; conversely, if the quality is slightly inferior and the supply exceeds the demand, the price may decrease.
Today, the price of this product on the market is roughly between [X1] yuan and [X2] yuan per kilogram. However, this is only an approximate number, and the actual price may vary depending on the place of transaction, the time of transaction, and the size of the batch. In prosperous commercial ports, due to strong demand, the price may be slightly higher; in remote places, the demand is slightly slower, and the price may be slightly lower. And if bulk transactions are made, merchants may give buyers a slight discount in order to promote sales, and the price will also drop.
Furthermore, the market situation changes, and the price of raw materials, production labor costs, and transportation tariffs can all affect the selling price of 3-hydroxy-4-methoxybenzoic acid. To know its exact price, you need to enter the market in person to investigate it in detail, or consult those who are familiar with the market in the industry to obtain its accurate price.