Which of the following compounds is/are secondary alkanols? i) CH3CH(CH3)CH3OH ii) CH3CH2CH(OH)CH3 iii) CH3C(OH)(CH3)CH3

Analyze the question: We need to identify which compounds are secondary (2°) alkanols. A secondary alkanol has the carbon bearing the -OH group attached to two other carbon atoms.

Concept:

• Primary (1°): the C-OH carbon is attached to one other carbon (e.g. CH3CH2OH)
• Secondary (2°): the C-OH carbon is attached to two other carbons
• Tertiary (3°): the C-OH carbon is attached to three other carbons

Solution:

i) CH3CH(CH3)CH3OH (written as CH3CH(CH3)CH2OH in its usual form, 2-methylpropan-1-ol). The C-OH carbon is CH2(OH), attached to only one carbon (the CH). So it is primary.

ii) CH3CH2CH(OH)CH3 (butan-2-ol). The C-OH carbon is attached to CH2CH3 and CH3, which is two carbons. So it is secondary.

iii) CH3C(OH)(CH3)CH3 (2-methylpropan-2-ol). The C-OH carbon is attached to three CH3 groups. So it is tertiary.

Only compound ii is a secondary alkanol.

Answer: B (II only).

Tip: Look only at the carbon holding the -OH and count the carbons directly attached to it: 1 = primary, 2 = secondary, 3 = tertiary. Ignore the rest of the chain.