Give the mechanism of cynohydrin formation when acetadehyde react with HCN in the presence of NaOh
Answers
Answer:
Hydrogen cyanide (HC≡N), adds reversibly to aldehydes and many ketone forming hydroxyalkanenitrile adducts (commonly known and called as cyanohydrins). Cyanohydrins have the structural formula of R2C(OH)CN. The “R” on the formula represents an alkyl, aryl, or hydrogen.
Figure 19.6.1: General Reaction of Cyanohydrin Formation
An important feature of cyanohydrin formation is that it requires a basic catalyst. Since hydrogen cyanide itself is an acid (pKa = 9.25), the best results occur when a small amount of a strong base activates hydrogen cyanide by converting it to cyanide ion ((-)C≡N), which can function as a carbon nucleophile. In the absence of base, the reaction does not proceed, or is at best very slow. Cyanohydrin formation is weakly exothermic, and is favored for aldehydes, and unhindered cyclic and methyl ketones.
Explanation:
Hydrogen cyanide (HC≡N), adds reversibly to aldehydes and many ketone forming hydroxyalkanenitrile adducts (commonly known and called as cyanohydrins). Cyanohydrins have the structural formula of R2C(OH)CN. The “R” on the formula represents an alkyl, aryl, or hydrogen.
Figure 19.6.1: General Reaction of Cyanohydrin Formation
An important feature of cyanohydrin formation is that it requires a basic catalyst. Since hydrogen cyanide itself is an acid (pKa = 9.25), the best results occur when a small amount of a strong base activates hydrogen cyanide by converting it to cyanide ion ((-)C≡N), which can function as a carbon nucleophile. In the absence of base, the reaction does not proceed, or is at best very slow. Cyanohydrin formation is weakly exothermic, and is favored for aldehydes, and unhindered cyclic and methyl ketones.