Q.Which of the following is a tertiary alcohol?

An alcohol is classified 1°/2°/3° by how many carbon atoms are directly attached to the carbinol (C-OH) carbon.

• Ethyl alcohol, CH3CH2OH: C-OH carbon attached to 1 carbon -> 1°
• Ethylene glycol, HOCH2CH2OH: both C-OH carbons attached to 1 carbon each -> 1°,1° (diol) …

Alcohols contain -OH bonded to an sp3 carbon; primary, secondary and tertiary alcohols correspond to -CH2OH, >CH-OH and >C-OH — so all the given groups represent alcohols.

The characteristic functional group of an alcohol is the hydroxyl group (-OH) attached to a saturated (sp3) carbon atom. Depending on how many carbon atoms are attached to the carbon bearing -OH:

• Primary (1°) alcohol: -CH2OH
• Secondary (2°) alcohol: >CH-OH …

Butan-2-ol: OH is on C-2, which is bonded to two carbons -> secondary alcohol.

Butan-2-ol is CH3-CH(OH)-CH2-CH3. The carbon carrying the -OH group (C-2) is joined to two other carbon atoms (C-1 and C-3). An alcohol is classified by the number of carbons attached to the C-OH carbon …

Option (b), 2-methylbutan-2-ol, has -OH on a carbon bonded to three carbons -> tertiary.

A tertiary alcohol has its -OH group on a carbon attached to three other carbon atoms.

• (a) CH3CH2OH: -OH carbon bonded to 1 carbon -> primary
• (b) CH3-C(CH3)(CH2CH3)-OH: the -OH carbon is bonded to CH3, CH3 and CH2CH3 = three carbons -> tertiary …

The carbon carrying -OH in butan-2-ol is bonded to two carbons, making it a secondary alcohol.

Butan-2-ol is CH3-CH(OH)-CH2-CH3. Classify an alcohol by the number of carbon atoms attached to the carbon that bears the -OH group:

• primary = 1 carbon attached
• secondary = 2 carbons attached
• tertiary = 3 carbons attached …