Dihydric alcohols Glycols

Dihydric alcohols (Glycols) They are saturated hydrocarbons in which 2 hydrogen atoms are replaced by 2(OH) groups. They are classified into α, β, γ according to the relative position of the OH groups in the molecule.

Dihydric alcohols (Glycols)

Preparation: 1. Mild oxidation

Dihydric alcohols (Glycols) Preparation: 2. Reduction of glyoxal:

Dihydric alcohols (Glycols) Preparation:

Dihydric alcohols (Glycols) Chemical reactions:

Dihydric alcohols (Glycols) Chemical reactions: 2- When treated with a dehydrating agent, it is dehydrated and cyclised to a heterocyclic compound called dioxane.

Dihydric alcohols (Glycols) Chemical reactions: 3- Oxidation:

Dihydric alcohols (Glycols) Chemical reactions: 4- Ether formation The ethyl ether is named Cellosolve because it is a good Solvent to cellulose nitrate (it has two function groups - O - & OH) it is also used in manufacture of lacquers.

Ethers

General formula R – O – R´ Ethers are considered as water molecules in which the two hydrogen atoms are replaced by two organic radicals. Also they are regarded as the anhydrides of the alcohols

Ethers Ethers are divided into two groups: 1. Simple ethers: R – O – R

Ethers 2. Mixed ethers: R – O - R´

Ethers Preparation: 1- By continuous etherification process, heating excess ethyl alcohol with cone. H 2 SO 4.

Ethers Preparation: 2- William Son's synthesis:

Ethers Chemical Reactions: 1- Formation of oxonuim salt: The formation of salts shows that ethers are basic in character (i.e. electron doner).

Ethers Chemical Reactions: 2- When treated with chlorine or bromine, ethers undergo substitution reactions. In the dark, diethyl ether reacts with chlorine to form α-chlorodiethylether, further chlorination yields α,α´-dichlorodiethyl ether.

Ethers In presence of light, total chlorination occurs and perchlorodiethyl ether is formed.

Ethers The most important ethers is diethylether, it is generally known as sulphuric ether, it is colorless liquid, boiling point 35°C, difficulty soluble in water, and highly inflammable, it is used in surgery as anesthesia.

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