Properties of alcohols

Some of the properties of alcohols resemble those of water, particularly their solvent properties and the chemical reactions of the OH group. They differ most in their toxicity. Only ethanol is non-poisonous in small quantities and low concentrations.
Also, the members of the alcohols with lower molecular weights exhibit ‘hydrogen bonding’. This is a linking bond between the O of one molecule and the H (of the OH) of another molecule, holding them slightly more strongly together. Hydrogen bonds are not as strong as the normal C OH bonds or C C bonds. Hydrogen
bonding (Figure 3.2) is discussed in detail in Section 8.1. You can see that there is a linking up of the O and H of two adjacent molecules via a weak bond called hydrogen bonding.
This hydrogen bonding makes the boiling points higher than expected because of the extra forces holding the alcohol molecules together and its hydrogen bonding with water if in solution. For example, ethanol boils at 78 C whereas its molecular weight might lead you to expect it to boil at about 40 C. Energy is needed to break these hydrogen bonds to convert the liquid into its vapour.