Question

Distinguish among primary, secondary, and tertiary alcohols. Give a structural formula for an example of each type.

Short answer

Primary, secondary, and tertiary alcohols differ in the carbon atom to which the hydroxyl group (-OH) is attached. In primary alcohols (1°), the hydroxyl group is attached to a carbon with only one other carbon atom bonded, like in ethanol (H_3C-CH_2-OH). In secondary alcohols (2°), the hydroxyl group is attached to a carbon with two other carbon atoms bonded, as in isopropanol (H_3C-CHOH-CH_3). In tertiary alcohols (3°), the hydroxyl group is attached to a carbon with three other carbon atoms bonded, such as tert-butanol (H_3C-C(OH)-C_3).

Step-by-step solution

Primary Alcohol

Primary alcohols (1° alcohols) have the hydroxyl group (-OH) attached to a carbon atom that is bonded to only one other carbon atom. An example of a primary alcohol is ethanol: H H | | H-C-C-OH | H In the structural formula above, the hydroxyl group is attached to a carbon which has only one other carbon atom bonded to it.

Secondary Alcohol

Secondary alcohols (2° alcohols) have the hydroxyl group attached to a carbon atom that is bonded to two other carbon atoms. An example of a secondary alcohol is isopropanol (isopropyl alcohol): H H H | | | H-C-C-C-OH | | H H In the structural formula above, the hydroxyl group is attached to a carbon which has two other carbon atoms bonded to it.

Tertiary Alcohol

Tertiary alcohols (3° alcohols) have the hydroxyl group attached to a carbon atom that is bonded to three other carbon atoms. An example of a tertiary alcohol is tert-butanol (t-butyl alcohol): H H H | | | H-C-C-C-OH | | | H H H In the structural formula above, the hydroxyl group is attached to a carbon which has three other carbon atoms bonded to it.