Alcohols Phenols and Ethers- Definition, Notes and Alcohols Phenols and Ethers Properties
Definition of Alcohols and Phenols
Hydroxy derivatives of aliphatic hydrocarbons are called alcohols while hydroxy derivatives of benzene are called phenols.
Properties of Alcohols
- Due to strong hydrogen bonding between molecules of alcohol, they have higher boiling point as compared to molecules of alkane having same molecular mass.
- Ethyl alcohol reacts with dehydrated CaCl2 to form crystalline solid compound CaCl2 .4C2H5OH.Hence to dry ethyl alcohol, dehydrated CaCl2 is not used.
- As the molecule are weight increases surface area also increases due to increase in van der Waal’s forces. As a result melting point increases.
Uses of Alcohol
Alcohol is used in cosmetics, since it is a good solvent with inert nature. It is not toxic in nature.
Classification of Primary (1), Secondary (2) and Tertiary (3) Alcohols
Mixture of dehydrated ZnCl and concentrated HCl in 1:1 ratio is known as lucas reagent. It is used for identification of primary, secondary and tertiary alcohols. In this reaction
- Tertiary (3) Alcohols, develop haziness immediately
- Secondary (2) Alcohols, develop haziness in 5 minutes
- Primary (1) Alcohols do not show haziness at normal temperature, but on heatings they show haziness.
They Are hydroxide derivatives of aromatic hydrocarbons and in this one or more then one groups are joined to aromatic ring. Phenol act as antiseptic (0.2%) and disinfectant ( 1% solutions ) both.
Nomenclature of Phenols
The simplest hydroxy derivative of benzene is final. It is its common name and also an accepted IUPAC name. As the structure of phenols involves a benzene ring in its substituted compounds the terms orto (1,2-disubstituted), meta (1,3-disubstituted) and para (1,4-disubstituted) are often used in the common names.
Physical properties of phenol
- The boiling points of phenol increases with increase in number of C-atoms.
- The solubility of alcohols in water is due to their ability to form H-bonds with increase in size of aryl groups.
Liebermann’s Test of Phenol
In this test phenol is heated with mixture of nitrite (NaNO ) and conc. H SO, then a typical blue-green colour is obtained . On diluting the mixture with water it turns red in colour and then mixing sodium hydroxide solution it agains turns blue.
Ethers are represented as R-OR’ and have general formula CnH2n+2O . Ethers are dialkyl derivatives of water or monoalkyl derivatives of alcohols. The IUPAC name of ether is alkoxy alkanes.
Difference between Alcohols and Ether
Due to presence of strong hydrogen bonding in Alcohols its boiling point is higher than ethers with same atoms and they exist in liquid state whereas in ethers, hydrogen bond are not formed thus their boiling points are low and they exist in gaseous state.
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