Why the boiling point of ethyl alcohol is much higher than that of dimethyl ether through both have the same molecular weight? 

Alcohols have much higher boiling points than the comparable, alkenes or the related ethers because molecules of alcohols can interact through H – bonding while those of alkenes and ethers cannot. Thus, ethanol has a higher boiling point (78°C) than dim ethyl ether (-25°C) though they have the same molecular weight.