glycerol properties
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Propane-1,2,3-triol or glycerol
Structure of Glycerol:
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Glycerol properties-
Physical properties:
1) It is colorless, odorless, viscous and hydroscopic liquid.
2) It is sweet in taste and non-toxic in nature.
3) It is soluble in water due to formation of hydrogen bonding .
4) It has high boiling point i.e 2900C. The high viscosity and high boiling point of glycerol are due to association through H-bonding.
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Chemical properties:
The molecule of glycerol contains two primary alcoholic (-OH) group and one secondary alcoholic (-OH) group hence it shows characteristics of both primary and secondary alcohols. Primary -OH groups are more reactive than secondary -OH group.
1. Reaction with Sodium ( Na) :
Primary alcoholic groups react with sodium one by one and secondary alcoholic group does not react. Then Mono sodium glycerolate is obtained at room temperature while disodium glycerolate at higher temperature.
2. Reaction with PCl5:
All three -OH groups are replaced by Cl atoms and glyceryl tri chloride is formed.
3. Reaction with HCl :
when HCl is passed into glycerol at 110oC then glycerol-α- monochloro hydrin & glycerol-β- monochlorohydrin are formed. If HCl gas is passed for sufficient time then glycerol-α, α’-dichlorohydrin and glycerol-α,β- dichlorohydrin are formed.
4. Reaction with HBr :
When HBr reacts at 110oC then glycerol-α- mono bromo hydrin & glycerol-β- mono bromo hydrin are formed. If HBr reacts for sufficient time then glycerol-α, α’-di bromo hydrin and glycerol-α,β- di bromo hydrin are formed.
5. Reaction with HI :
a) When glycerol is warmed with small amount of HI then allyl iodide is formed.
b) When glycerol is heated with large amount of HI, then allyl iodide first formed is reduced to propene . In presence of excess of HI iso-propyl iodide is formed.
6) Dehydration:
Glycerol when heated alone or with dehydrating agents such as KHSO4 or P2O5 or concentrated H2SO4, then acrolein or acraldehyde is formed, which has a characteristic bad smell.