Organic acid
Organic acids refer to some organic compounds with acidic properties. The most common organic acids are carboxylic acids, which derive their acidity from the carboxyl group (-COOH). Sulfonic acid (-SO3H), sulfinic acid (RSOOH), sulfuric acid (RCOSH), etc. also belong to organic acids. Organic acids can react with alcohols to form esters.
It is widely distributed in leaves, roots, and especially fruits of Chinese herbal medicines, such as black plum, schisandra, raspberry, etc. Common organic acids in plants include aliphatic monobasic, dibasic, and polycarboxylic acids such as tartaric acid, oxalic acid, malic acid, citric acid, ascorbic acid (i.e. vitamin C), etc., as well as aromatic organic acids such as benzoic acid, water, etc. Salicylic acid, caffeic acid (Caffelc acid), etc.
Except for a few that exist in a free state, they are generally combined with potassium, sodium, calcium, etc. to form salts, and some are combined with alkaloids to form salts. Fatty acids are often combined with glycerol to form esters or with higher alcohols to form waxes. Some organic acids are constituents of volatile oils and resins.
Carboxyl group is the functional group of carboxylic acid. Except formic acid (H-COOH), carboxylic acid can be regarded as the derivative of hydrogen atom in hydrocarbon molecule replaced by carboxyl group. Available general formula (Ar) R-COOH represents. Carboxylic acids often exist widely in nature in the free state or in the form of salts and esters.
The derivatives in which the hydrogen atoms on the hydrocarbon group in the carboxylic acid molecule are replaced by other atoms or atomic groups are called substituted carboxylic acids. Important substituted carboxylic acids include halogenated acids, hydroxy acids, keto acids and amino acids. Some of these compounds participate in the biological hydroxylation of animal and plant metabolism, some are intermediate products of metabolism, some have significant biological activity, can prevent and cure diseases, and some are raw materials for organic synthesis, industrial and agricultural production and pharmaceutical industry.
Common Organic Acids in Food
Common organic acids in food include citric acid, malic acid, tartaric acid, oxalic acid, succinic acid, lactic acid and acetic acid. Some of these organic acids are inherent in food raw materials, such as organic acids in fruits, vegetables and their products; some are added in food processing, such as organic acids in soft drinks; Organic acids in vinegar.
A food can contain one or more organic acids at the same time. For example, apples mainly contain malic acid (1.02%), and citric acid is less (0.03); spinach mainly contains oxalic acid, and also contains malic acid and citric acid. The acid in some foods is considered to be added, so it is relatively simple. For example, cola mainly contains phosphoric acid.
Features
Organic acids are mostly soluble in water or ethanol, showing a significant acidic reaction, and hardly soluble in other organic solvents. Volatile or not. When calcium chloride, lead acetate or barium hydroxide solution is added to the aqueous solution of organic acid, the precipitation of insoluble calcium salt, lead salt or barium salt can be formed. These methods can often be used to remove organic acids from Chinese herbal medicine extracts.
Inorganic acid
Inorganic acid is a general term for acids in inorganic compounds. Inorganic acids are generally inorganic compounds that can dissociate hydrogen ions. According to the composition, inorganic acids can be divided into oxyacids, anaerobic acids, complex acids, mixed acids, superacids, etc.,
According to the degree of dissociation, they can be divided into strong acids and weak acids, and according to the number of hydrogen ions that can be ionized in the molecule The number is divided into monobasic acid, dibasic acid and polybasic acid. Inorganic acids are mostly used to provide hydrogen ions.
Difference Between Organic Acids and Inorganic Acids, Compare the Difference Between Similar Terms
1. The difference in stability
Inorganic acids are generally more stable than organic acids (except for a few such as carbonic acid), because organic acids usually have lower melting and boiling points and are easily decomposed when heated to high temperatures, while inorganic acids can usually withstand 200 degrees Celsius.
2. The difference between acidity
Most organic acids are weak (except for a few, such as HOOC-COOH). Inorganic acids such as the three major acids are more acidic.
3. The difference in molecular weight
The molecular weight of inorganic acids is generally lower than that of organic acids, because many carbon chains can be inserted into organic acids.
