Common Reagents & Conditions — Organic Chemistry Mnemonic
Target: mnemonic for organic chemistry reagents and conditions
Why is this hard to memorize?
Organic chemistry exam questions often boil down to knowing which reagent does what. LiAlH₄ vs NaBH₄, KMnO₄ vs OsO₄, PCC vs Jones reagent — these distinctions decide whether you get the right product. NEET and JEE test your ability to pick the correct reagent for a transformation and to predict what product a given reagent will produce. The key is to group reagents by function: oxidizing agents (KMnO₄, K₂Cr₂O₇, PCC), reducing agents (LiAlH₄, NaBH₄, H₂/Pd), dehydrating agents (conc. H₂SO₄, Al₂O₃), and halogenating agents (SOCl₂, PBr₃, HX).
Classic mnemonics you should know
"LiAlH₄ Loves All, NaBH₄ Nice But Humble — H₂/Pd Handles Plainly"
LiAlH₄(Loves All) = strongest, reduces almost everything. NaBH₄(Nice But Humble) = milder, only reduces aldehydes/ketones. H₂/Pd(Handles Plainly) = catalytic, reduces C=C and C≡C.
"PCC Partially, Jones Jumps, KMnO₄ Kills"
PCC(Partially) = mild oxidation (primary alcohol → aldehyde, stops there). Jones(Jumps) = stronger (primary alcohol → carboxylic acid). KMnO₄(Kills) = strongest (breaks double bonds, oxidizes everything).
"SOCl₂ Silently, PBr₃ Professionally, HX Honestly"
SOCl₂ = converts OH to Cl (gaseous byproducts escape — "silent"). PBr₃ = converts OH to Br (clean, professional). HX = direct addition (honest, straightforward).
The complete list
- LiAlH₄ (strong reductant)
- NaBH₄ (mild reductant)
- H₂/Pd (catalytic hydrogenation)
- PCC (mild oxidant)
- Jones reagent (strong oxidant)
- KMnO₄ (strongest oxidant)
- SOCl₂ (OH→Cl)
- PBr₃ (OH→Br)
- conc. H₂SO₄ (dehydration)
- Na/liquid NH₃ (Birch reduction)
- OsO₄ (syn-hydroxylation)
- mCPBA (epoxidation)
Frequently asked questions
How do I remember when to use LiAlH₄ vs NaBH₄?
LiAlH₄ is the "powerful" one — it reduces COOH, COOR, CONH₂, CHO, CO all to alcohols/amines. NaBH₄ is "gentle" — it only reduces CHO and CO (aldehydes and ketones) to alcohols. When in doubt, LiAlH₄ works for everything, NaBH₄ is selective.
Why does PCC stop at aldehyde but Jones goes to carboxylic acid?
PCC (pyridinium chlorochromate) works in anhydrous CH₂Cl₂ — no water present means the aldehyde formed cannot be further oxidized. Jones reagent (CrO₃/H₂SO₄/acetone) is aqueous, so the aldehyde first forms a hydrate which is then further oxidized to the acid.
What is the difference between syn and anti hydroxylation?
OsO₄ gives syn-addition (both OH groups on same face) via a cyclic osmate ester. KMnO₄ (cold, dilute) also gives syn-hydroxylation. For anti-hydroxylation, use mCPBA (to form epoxide) followed by acid-catalyzed ring opening.
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