Why can glycogen react with iodine solution to appear reddish brown?

Glycogenus"Animal starch", which is an energy storage substance for animals and bacteria, has a structure similar to amylopectin, and is reddish-brown when exposed to iodine.

Amylose is blue when exposed to iodine, amylose is purple when iodine, and glycogen is red (reddish-brown) when iodine.

I think it's an iodoform reaction.

Glycogen. energy storage for animals and bacteria; , the structure is similar to that of amylopectin, reddish-brown when exposed to iodine, blue when exposed to iodine, purple when exposed to iodine, and red (reddish-brown) when glycogen is met with iodine.

Generally, metals that can react with chlorine (except for ***) can also react with iodine, but the reactivity is not as good as chlorine. For example, noisy silver such as iodine can directly interact with active metals at room temperature, and the reaction with other metals needs to occur at higher temperatures.

Generally, non-metals that can react with chlorine can also react with iodine, because the oxidation ability of iodine is weak, and the reactivity is not as good as chlorine, so it needs to be at a higher temperature before the reaction can occur.

Glycogen is here:"Animal starch", energy storage substances for animals and bacteria;

The structure is similar to that of the branched chain starch.

It is reddish-brown when exposed to iodine.

Amylose is auspicious blue when exposed to iodine, amylopectin is purple when exposed to iodine, and glycogen is red (reddish-brown) when exposed to iodine.

The oxidation reaction can occur between the two, but the reaction is extremely slow, so the color is the color of iodine after adding to the mixture.

The chemical properties of iodine are not as active as the group elements F2, Cl2 and Br2, but it can also exhibit a variety of oxidation states from -1 to +7 in chemical reactions, and its chemical properties can be summarized as follows.

1. Reaction between iodine and non-metals:

Generally, non-metals that can react with chlorine can also react with iodine, because the oxidation ability of iodine is weak, and the reactivity is not as good as chlorine, so it needs to be reacted at a higher temperature.

2. Reaction between iodine and metals:

Generally, metals that can react with chlorine (except ***) can also react with iodine, but the reactivity is not as good as chlorine.

3. Reaction between iodine and water:

1) The type of reaction between halogen and water is noisy: self-redox reaction will occur in water.

2) Reaction between iodine and water: The solubility of iodine in water is the smallest, only slightly soluble in water, and the solubility is the envy of water.

The main structural difference between glycogen and amylopectin is that glycogen has about 8 12 more branches of glucose, and there are 12 18 glucose molecules in the branches. (Amylopectin generally has a branch every 24 to 30 glucose).

As a result, the inclusion complex formed by glycogen and I2 is different from that of the lake chain combustion powder, and the wavelength band of light absorption will be different.

Presented in Li Zhaoyuan red.

Dextrin, starch, and glycogen meet I2 for color development, and they are all inclusion complexes that form polymer-iodine. The principle is similar.

Glucose is a monomer of starch, that is, starch is a high molecular weight polymer formed by the polymerization of glucose, starch is divided into amylose and amylopectin, which is different from iodine discoloration reaction, the branch chain will become reddish-brown, the direct connection will become blue-purple, starch does not redivide hydrolysate, that is, dextrin will produce blue, brown, yellow and other different colors with iodine, dextrin continues to hydrolyze, that is, starch is completely hydrolyzed to produce glucose and iodine will not undergo discoloration reaction.

Iodine does not change color when it meets glucose, and discoloration when it meets iodine is the characteristic of starch, and starch is a polymer of glucose, but the properties of the polymer and the monomer that compose it are not necessarily the same.

Glucose and iodine cannot react, so the solution is still the brown color of iodine solution. It is starch that can react with iodine to develop color.

The blue-coloured change of starch when exposed to iodine is a chromogenic reaction.

It was proved that the chromogenic of iodine and starch was mainly due to the formation of inclusion complexes in addition to adsorption causes. The color of the cladding complex produced by starch and iodine is related to the degree of polymerization or relative molecular weight of starch. In a certain range of polymerization or relative molecular mass, with the increase of polymerization degree or relative molecular weight, the color of the inclusion complex changes from colorless, orange, light red, purple to blue.

For example, when the degree of polymerization of amylose is 200 980 or the relative molecular mass range is 32 000 160 000, the color of the inclusion complex is blue. Amylopectin, which has a lot of branches, has an average degree of amylopectin on the branched chain with an average degree of polymerization of 20 28, and the inclusion complex thus formed is purple. The degree of polymerization of dextrin is lower, showing brownish-red, red, light red, etc.

It is a chromogenic reaction; The color development mechanism of starch and iodine is that amylose is blue when exposed to iodine, amylopectin is purple-red when exposed to iodine, and dextrin is blue-violet, purple, orange and other colors when exposed to iodine. These chromogenic reactions are highly sensitive and can be used as a quantitative and qualitative method for identifying starch, as well as for the analysis of iodine content.

Please refer to:

Iodine does not change color when exposed to glucose. Spike iodine is soluble in many organic solvents, such as chloroform, carbon tetrachloride. The solution of iodine produced in ethanol and ether is brown.

Iodine produces purple solutions in solvents with a small dielectric constant (e.g., carbon disulfide, carbon tetrachloride), in which iodine exists in a molecular state. Although the solubility of iodine in water is small, the solubility of potassium iodide ki or other iodide solutions is significantly increased.

Generally, the non-metals that Sun Yu can react with chlorine can also react with iodine, because the oxidation ability of iodine is weak, and the reactivity is not as good as chlorine, so it needs to react at a higher temperature. For example, it reacts with phosphorus to produce only phosphorus triiodide.