About 1835, French chemists Payan and Peruz published a theory about studying the composition of various plant cell walls, and determined that one of them, which is isomeric with starch, can be hydrolyzed into monosaccharide, which is called cellulose from French "cell".
Wood contains a lot of cellulose and lignin. Lignin is not a carbohydrate and cannot be hydrolyzed into monosaccharides. It is the source of methanol produced by dry distillation of wood, because its molecule contains methoxy (CH3O—-). Payan found the method of separating cellulose from lignin in 1842. Nitric acid dissolves lignin and separates it from cellulose. Sulfuric acid dissolves cellulose, leaving lignin.
But the name carbohydrate does not reflect their structural characteristics. First, hydrogen and oxygen do not exist in the form of water in carbohydrate molecules. In addition, it has been found that the ratio of hydrogen to oxygen in some carbohydrate molecules is not always equal to 2: 1. For example, in 1879, German chemist Hamberger hydrolyzed quercetin in oak to obtain rhamnose (C6H 12O5). Some compounds equal to 2∶ 1, such as C2H4O2 acetate and C3H6O3 lactate, cannot be classified as carbohydrates in nature. Even so, the name has survived. China chemists once created "sugar" to replace it. Now the word "sugar" is often used in some chemistry textbooks. They are divided into monosaccharide, disaccharide and polysaccharide. Monosaccharide and formula sugar are also called sugar, and polysaccharide is called polysaccharide.
Starch (C6H 10O5)n in polysaccharide is widely distributed in nature, and the starch content in the seeds of cereals and beans is the most, which has been people's main food since ancient times, and people have long known it.
18 1 1 year, G·S· Kirchhoff, a German pharmacist in Petersburg, Russia, found that starch paste was heated with dilute sulfuric acid and converted into sugar in grape juice. Then in 18 19, French chemist Bracano cooked cellulose with sulfuric acid and also got the sugar in grape juice. This reveals the secret of the composition of starch and cellulose, and also becomes the enlightenment of making glucose from starch, cellulose-containing sawdust and shavings today.
1833, Peruz discovered that starch can not only produce glucose, but also produce a kind of glue called "dextrin".
Starch is hydrolyzed by dilute sulfuric acid to produce a series of products, first dextrin, then maltose and finally glucose.
Dextrin is a kind of polysaccharide whose molecule is smaller than starch. It can be dissolved in water to form a colloidal solution and is often used as a paste.
Animal starch was found in polysaccharide by French physiologist Bellard in 1857. It is called "producer of sugar" and "glycogen". Unlike starch, it is more soluble in hot water and does not form a viscous solution. It mainly exists in the liver. Its function is to store carbohydrates and break them down into monosaccharides when needed. Under normal circumstances, due to the interaction of these substances, the sugar content in our blood remains stable.
The main sugars are sucrose, maltose and lactose.
According to the records of Spanish colonists, ancient Mexican Indians made sugar with corn stalks and agarwood, while North American Indians cooked sugar with maple juice. Making sugar from sugarcane may be an Indian invention. In 300 BC, sugarcane was used to make sugar in eastern India. Sugarcane originated in New Guinea, and was used only for chewing and eating by local residents for a long time, and later spread to India. In the 7th century, the imperial court of China sent people to India to learn the method of sugar production. After they returned to China, they began to make sugar in Yangzhou. In the 8th century, Arabs introduced sucrose to European countries.
1747 French chemist Magraff discovered sucrose in sugar beet. His student Achard has been engaged in the industrial production of beet sugar since 1786. 1799, he gave a cone-shaped sucrose block made of beet juice to William III, the Prussian emperor, and got financial help. He set up a factory in 1802 and started production.
1833, Dubrunff, a professor of industrialization at Paris Business School and a producer of sugar, discovered that sucrose was hydrolyzed by acid to produce glucose and fructose, which was called invert sugar, which was sweeter than the original sucrose and was used to make soft white sugar, medicine, beer, candy and cakes. This opens up a way for people to understand the composition of sucrose.
Later, it was found that honey is invert sugar. The nectar collected by bees from flowers mainly contains sucrose, which contains invertase, which can hydrolyze sucrose. But honey is not pure invert sugar. Besides glucose and fructose, it also contains some sucrose.
In ancient China, maltose was the main sweet food, and maltose was still called maltose in China. When we chew rice carefully in our mouth, it will become sweeter and sweeter, because the starch in rice is converted into maltose by salivary amylase in saliva. People in ancient China knew that at least around 1000 BC, malt in starch grains began to produce maltose. Malt contains starch glucoamylase, which can convert starch into glucose. Payan and Peruz isolated this enzyme from malt at 1833.
Maltose is hydrolyzed by acid and only glucose can be obtained. Maltose is easily digested into glucose in human body. Most commercially available malt extract cod liver oil is maltose.
Lactose exists in the milk of mammals and humans, with 5% ~ 7% in human milk and 4% ~ 5% in milk.
In 1856, Pasteur hydrolyzed the sugar in milk to obtain a sugar called lactose. 1860, French chemist Berthelot determined that the sugar in milk was hydrolyzed by Pasteur to get galactose, and the sugar in milk was lactose. Galactose is a monosaccharide, which is the product of lactose hydrolysis. The products of lactose hydrolysis are galactose and glucose, which are different from sucrose and maltose.
Besides galactose, monosaccharides are mainly glucose and fructose. German professor of applied mathematics 1792 obtained glucose from grape juice and determined that it was a sugar different from sucrose. Later in 18 1 1 and 18 19, Kirchhoff and Brakono were obtained from hydrolyzed starch and cellulose, respectively. But it was not until 1838 that Perigau, a French chemical tomb, was identified and named glucose. Perigaud also found that the honey and urine of diabetic patients contain glucose. China Ming Dynasty Wang Shimao's Yule Tan Wei said that the urine of diabetics is sweet. 1776, British doctor Dobson also identified that the urine of diabetic patients contains sugar. This is because the patient's glucose metabolism is abnormal, and the blood sugar concentration is particularly high, so it is often excreted from the urine.
Fructose is widely found in fruit juice, which is the sweetest of common sugars, but it has not been regarded as a substance different from other sugars for a long time. It was not until 1833 that Dubrunff discovered that sucrose was hydrolyzed by acid into glucose and fructose. Dibenfluridose is easy to crystallize from aqueous solution, and their calcium salts have different solubility in water. The existence of fructose is determined by separating them.
1880, Chirianni, a German organic chemist, observed that glucose was rapidly oxidized by bromine to gluconic acid CH2OH(CHOH)4COOH, while fructose was only slowly oxidized by bromine, and HOCH2COOH glycolic acid was produced a few weeks later. So he determined that glucose is aldose and fructose is ketose, because aldehydes are easily oxidized into carboxylic acids with the same number of carbon atoms, while ketones are not easily oxidized. In 1886, in order to determine the number of carbon atoms and the position of carbonyl groups in glucose and fructose, he carried out the addition reaction of hydrocyanic acid (HCN) with glucose and fructose. This is a method of synthesizing higher sugar from lower sugar by increasing carbon atoms. The product is reduced to obtain heptanoic acid and isoheptanoic acid with seven carbon atoms. So he gave the chemical formula of glucose: CH2OH(CHOH)4CHO, and the chemical formula of fructose: CH2OHCO(CHOH)3CH2OH.
This clearly distinguishes the molecular structures of glucose and fructose.
In 1887, E. Fisher studied the glucose molecule from stereochemistry and found that it has 16 spatial isomers.
It was not until 1929 that the British chemist Haworth published "The Structure of Sugar" that it was clearly affirmed that monosaccharides such as glucose had a cyclic structure.
Haworth further determined the structures of many carbohydrates, and proposed that disaccharides such as sucrose, maltose and lactose are molecules formed by combining two monosaccharide units through oxygen bridges, while cellulose and starch are also formed by connecting glucose with different configurations.