Copper hydroxide
Copper hydroxide, molecular formula Cu(OH)2, dry powder appears blue or crystal, insoluble in water, decomposed by heat, slightly amphoteric, soluble in acid, ammonia and sodium cyanide, easily soluble in alkaline glycerin In the solution, it becomes dark when heated to 60-80°C, and decomposes into black copper oxide and water at higher temperatures. It is slightly toxic and is used as an analytical reagent, as well as in medicine, pesticides, etc.; it can also be used as a catalyst, mordant, pigment, and feed. Additives, paper dyes, swimming pool disinfectants, etc.; it is also a weak oxidant.
Benzaldehyde
Benzaldehyde is an organic compound formed by replacing the hydrogen of benzene with an aldehyde group. Benzaldehyde is the simplest and most commonly used aromatic aldehyde in industry. It is a colorless liquid at room temperature with a distinctive almond odor. Benzaldehyde is the main component of bitter almond oil extract and can also be extracted from apricots, cherries, bay leaves, and peach pits. The compound is also present in glycoside-conjugated form in kernels and nuts.
Why can newly prepared copper hydroxide react with benzaldehyde
Benzaldehyde can react with newly prepared copper hydroxide suspension to form a brick-red precipitate, which is a common characteristic of substances containing aldehyde groups. Aldehydes are compounds composed of hydrocarbon groups connected to aldehyde groups, abbreviated as RCHO. The aldehyde group is also called formyl group. The structural characteristic of aldehyde molecules is that they contain aldehyde groups. Aldehydes are catalytically hydrogenated and reduced to alcohols, which are easily oxidized by strong oxidants or even weak oxidants. The aldehyde group has both oxidizing and reducing properties. The newly produced copper hydroxide has weak oxidizing properties, so the two can undergo a redox reaction. Benzaldehyde will be oxidized to benzoic acid, and copper hydroxide will be reduced to cuprous oxide.