Error Analysis — Common Mistakes in OC-05 — Notes

#	Common Error	Why Students Make It	Correct Understanding
1	Using $KMnO_{4}$ to stop at aldehyde	Confuse $KMnO_{4}$ as mild oxidant	$KMnO_{4}$ is STRONG; only PCC stops at aldehyde
2	Thinking 3° alcohol reacts fastest in esterification	Confuse stability with reactivity for esterification	3° alcohols are bulky — esterification is slowest for 3° due to steric hindrance
3	Using 3° halide in Williamson synthesis	Not considering SN2 requirement	3° halides give E2 (elimination) with strong alkoxide; must use 1° halide
4	Saying Lucas test requires heating for 2° alcohol	Confusing test conditions	2° gives turbidity at RT in 5-20 min; no heating needed at RT
5	Assuming phenol undergoes nucleophilic substitution easily	Phenol has -OH like alcohol	Phenol -OH is not a good leaving group; it undergoes electrophilic aromatic substitution instead
6	Kolbe reaction product at para position	Forgetting ortho preference	Kolbe gives -COOH at ortho (steric factor with $Na^{+}$ guiding); Reimer-Tiemann also ortho
7	$NaBH_{4}$ reduces carboxylic acids	Thinking all hydrides are equal	$NaBH_{4}$ only reduces C=O of aldehydes/ketones; RCOOH needs $LiAlH_{4}$
8	Phenol + $Br_{2}$ needs $FeBr_{3}$ catalyst	Applies benzene conditions to phenol	-OH is strong activator; no Lewis acid needed for phenol bromination
9	Confusing pKa direction — lower pKa = more/less acidic	Inverse relationship not internalized	Lower pKa = more acidic; phenol pKa ~10 is more acidic than alcohol pKa ~16
10	Ether cleavage gives alcohol + alkyl iodide only	Stopping at first step of HI cleavage	Excess HI: R-O-R' → RI + R'OH → RI + R'I (both become iodides)