Physical property of ether

Dimethylether and ethyl methyl ether are gases at ordinary temperature. The other lower homologues are colorless, pleasant smelling, volatile liquids with typical ether smell.

Boiling points

The C - O bonds in ether are polar and thus ethers have a net dipole moment. The weak polarity of ethers do not appreciably affect their boiling points which are comparable to those of the alkenes of comparable molecular mass. Ethers have much lower boiling points as compared to isomeric alcohols. This is because alcohols molecules are associated by hydrogen bonds while ether molecules are not.

Solubility

Ethers containing up to 3 carbon atoms are soluble in water, due to their hydrogen bond  formation with water molecules. The solubility decreases with increase in the number of carbon atoms. The relative increase in the hydrocarbon portion of the molecule decreases the tendency of H-bond formation. Ethers are appreciably soluble in organic solvents like alcohol, benzene, acetone etc.

Chemical Properties of Ether

The functional group in ethers (-O-) is comparatively inert with respect to the -OH functional group in alcohols and phenols even though the oxygen atom in each of the groups has two lone pairs of electrones. Therefore, ethers are not easily attacked by alkalies, dilute mineral acids, PCl₅, metallic sodium etc. under ordinary conditions. But they undergo chemical reactions under specific conditions.

1. Cleavage of C-O bond in ethers

The cleavage of C-O bond in ethers takes palce under drastic conditions with excess of hydrogen halides. The reaction of dialkyl ether gives two alkyl halide molecules.

R-O-R + 2HX -------------> 2RX + H₂O

Alkyl aryl ethers are cleaved at the alkyl-oxygen bond. The reaction yields phenol and alkyl halide.

Ethers with two different alkyl groups are also cleaved in the same manner.

R-O-R + H-X ------------> R-X + R-OH

The order of reactivity of hydrogen halides is as follows: HI > HBr > HCl.