See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

A secondary alcohol is defined as an OH group attached to a carbon that is bonded to exactly two other carbon atoms (and one hydrogen). Step 1 - Analyze compound (I): The central carbon bearing OH has: the OH group, one H, one CH2OH group (carbon), and one ethyl chain (carbon). That central C is bonded to two carbons → secondary alcohol. Compound I contains a secondary alcohol. ✓ Step 2 - Analyze compound (II): The central carbon bearing OH has: OH, CH3, CH2OH, and ethyl substituents. That central carbon is bonded to THREE other carbons (CH3, the CH2 of CH2OH, and the ethyl chain) and NO hydrogen → this is a TERTIARY alcohol, not secondary. ✗ Step 3 - Analyze compound (III): The OH-bearing carbon has: OH, H, CHO (aldehyde carbon counts as a carbon substituent), and an ethyl group. That carbon is bonded to two carbons (CHO carbon and ethyl carbon) and one H → secondary alcohol. ✓ Step 4 - Analyze compound (IV): The structure is ethyl-C(=O)-CH2-OH. The OH is on a CH2 group, which is bonded to only ONE carbon (the carbonyl carbon) and TWO hydrogens → primary alcohol. No secondary alcohol present. ✗ Step 5 - Analyze compound (V): The upper OH group is on a carbon bearing: OH, H, CH3, and a bond to the rest of the chain → two carbon substituents → secondary alcohol. ✓ Step 6 - Analyze compound (VI): The central carbon has: two H atoms (wedge and dash), an ethyl group, and a CH2OH. The CH2OH carbon is bonded to only one carbon and two H's → primary alcohol. No secondary alcohol. ✗ Compounds with at least one secondary alcohol: I, III, V → option (d). Why other options fail: - (a) I, II, IV, VI: II is tertiary, IV and VI are primary; incorrect. - (b) I, III: misses V which also has a secondary alcohol; incorrect. - (c) I, II, III, V: II is tertiary not secondary; incorrect. Therefore, the correct answer is D.