PREPWISER.
Practise online

Practical Organic Chemistry revision notes

Every idea in the Practical Organic Chemistry chapter for JEE Main, with the usual mistakes and the fast methods. Topic 1 is open to everyone; sign in free to read all 18 and download the PDF.

Sign in to read all 18Download PDF

Read the first part free. Sign in free with Google to read the rest and download the PDF: 10 A4 pages.10 A4 pages, ready to print.

How we count: 7× asked means 7 past JEE Main questions in the PrepWiser bank needed that concept, and "last" is the latest year one appeared. ★ marks ideas asked 8 or more times.

Unsaturation, alcohols, phenols and acids

Tests for unsaturation
4× asked, last 2026
RCH=CHX2+BrX2→RCHBr−CHX2Br,RCH=CHX2→cold, diluteKMnOX4/OHX−RCH(OH)CHX2OH\ce{RCH=CH2 + Br2 -> RCHBr-CH2Br},\qquad \ce{RCH=CH2 ->[KMnO4/OH-][\text{cold, dilute}] RCH(OH)CH2OH}
Bromine water: red-orange colour fades. Baeyer's: pink of cold dilute alkaline KMnOX4\ce{KMnO4} fades and brown MnOX2\ce{MnO2} forms.
CompoundBromine water fadesHow (from the structure)Precipitate
hex-1-ene✓addition (C=C)none
phenol✓substitutionwhite ppt
aniline✓substitutionwhite ppt
benzene✗: :
cyclohexane✗: :
A non-ring C=C adds Br₂; an –OH or –NH₂ on the ring makes it substitute (and HBr forms).
Br₂ waterbeforedecolourisedwith C=Ccold KMnO₄beforeMnO₂ (brown)with C=C
Colour changes (sheet; colours illustrative)
  • Not proof of a C=C when bromine water fades. Phenols and aniline also use up bromine, but by substitution, giving a white precipitate and HBr. Addition to an alkene gives no precipitate.
Alcohols: CAN and Lucas tests
6× asked, last 2026
(NHX4)X2[Ce(NOX3)X6]+3 ROH→[Ce(NOX3)X4(ROH)X3]+2 NHX4NOX3ROH+HCl→ZnClX2RCl+HX2O:  3∘ turbid at once, 2∘ in 5 min, 1∘ not at room temp.\begin{gathered}\ce{(NH4)2[Ce(NO3)6] + 3ROH -> [Ce(NO3)4(ROH)3] + 2NH4NO3}\\ \ce{ROH + HCl ->[ZnCl2] RCl + H2O}:\ \ 3^\circ\ \text{turbid at once},\ 2^\circ\ \text{in 5 min},\ 1^\circ\ \text{not at room temp.}\end{gathered}
CAN: yellow turns red with any alcoholic –OH (1°, 2°, 3°). Lucas (conc. HCl + anhydrous ZnClX2\ce{ZnCl2}) then sorts the class.
CompoundClass (from structure)CANLucas
ethanol1°redclear at room temp.
propan-2-ol2°redabout 5 min
2-methylpropan-2-ol3°redturbid at once
benzyl alcohol1°, benzylicredturbid at once
phenolphenol (ring C–O): no reaction
CAN turns red with any alcoholic –OH; Lucas then sorts the class.
  • Lucas turbidity is the insoluble RCl; its speed follows carbocation stability, so benzyl and allyl alcohols react at once like 3°. Phenols do not react, as the ring C–O bond does not break.
  • Na metal frees HX2\ce{H2} from a dry alcohol, but it is not specific: water, phenols and acids also give HX2\ce{H2}.
Phenols: FeCl₃, bromine water, phthalein
8× asked, last 2026
6 CX6HX5OH+FeX3+→[Fe(OCX6HX5)X6]X3−+6 HX+  (violet)\ce{6C6H5OH + Fe^{3+} -> [Fe(OC6H5)6]^{3-} + 6H+}\ \ \text{(violet)}
Use neutral FeClX3\ce{FeCl3}; acid breaks up the complex. Enols also give a colour; alcohols give none.
AcidC=C (from structure)Neutral FeCl₃Bromine water
benzoic acid✗buff pptno change
cinnamic acid✓buff pptdecolourised
FeCl₃ sees only the carboxylate in both; bromine water sees the C=C.
phenolvioletacetatedeep redbenzoatebuff ppt
Neutral FeCl₃ (sheet; colours illustrative)
  • Bromine water gives a white precipitate of 2,4,6-tribromophenol at once, with no catalyst. Phthalein dye test: heat with phthalic anhydride and conc. HX2SOX4\ce{H2SO4}, then add NaOH; phenolphthalein shows pink-red.
  • Not only phenols colour neutral FeClX3\ce{FeCl3}. Acetate gives a deep red colour and benzoate a buff precipitate. So FeClX3\ce{FeCl3} cannot tell benzoic acid from cinnamic acid; bromine water can (cinnamic acid's C=C).
Carboxylic acids and solubility tests
3× asked, last 2026
RCOOH+NaHCOX3→RCOONa+HX2O+COX2↑,RCOOH+CX2HX5OH⇌HX+RCOOCX2HX5+HX2O\ce{RCOOH + NaHCO3 -> RCOONa + H2O + CO2 ^},\qquad \ce{RCOOH + C2H5OH <=>[H+] RCOOC2H5 + H2O}
Brisk effervescence with NaHCOX3\ce{NaHCO3} shows –COOH. Warming with ethanol and conc. HX2SOX4\ce{H2SO4} gives a fruity ester smell.
CompoundDissolves in NaOHNaHCO₃ fizzes
ethanoic acid✓✓
phenol✓✗
picric acid✓✓
benzenesulphonic acid✓✓
benzyl alcohol✗✗
4-(dimethylamino)phenol✓✗
Read off each structure: –COOH and –SO₃H free CO₂; a phenol does only with two or more o/p –NO₂ (picric acid); ArCH₂OH is not acidic.
benzoic acidanilinechlorobenzeneanilinechlorobenzenechlorobenzenein ethyl acetateNaOH(aq)water layerC₆H₅COO⁻ Na⁺dil. HClwater layerC₆H₅NH₃⁺ Cl⁻
Separating funnel: each compound’s layer decided from its structure (acid → NaOH, amine → HCl, neutral stays)
  • Not every –OH dissolves in NaOH. Only an acidic one: a ring –OH (phenol), –COOH or −SOX3H\ce{-SO3H}; ArCHX2OH\ce{ArCH2OH} is an alcohol and stays out. A ring –OH still dissolves when the ring also carries −NMeX2\ce{-NMe2}.
  • Not a carboxyl test for every 'acid'. Sulphanilic acid is a sulphonic acid with no –COOH, so it gives no ester test, though its N and S do show up in Lassaigne's test.
  • Not always –COOH when NaHCOX3\ce{NaHCO3} fizzes. Any acid stronger than HX2COX3\ce{H2CO3} gives COX2\ce{CO2}. Phenol does not, but picric acid (2,4,6-trinitrophenol) and sulphonic acids do.
  • Quick method. In a separating funnel, aqueous NaOH pulls only acids (as salts) into water; amines need dilute HCl, and neutral compounds never move. Benzoic acid leaves ethyl acetate; aniline and chlorobenzene stay.

Practise Practical Organic Chemistry questions as you read. Free, and you can start without signing up.

Practise Practical Organic Chemistry

14 more concepts in 6 topics

Aldehydes and ketones, Amines, Syllabus preparations, Titrimetric analysis and Physical experiments (NTA list), plus ideas from Purification, Mole concept. Read the first part free. Sign in free with Google to read the rest and download the PDF.

Sign in to read the restYou come straight back to this spot.Download the PDF

Aldehydes and ketones

  • 2,4-DNP test: any aldehyde or ketone2×
  • Tollens', Fehling's, Benedict's, Schiff's7×
  • Iodoform test and preparation2×

Amines

  • Carbylamine test: 1° amines only3×
  • Hinsberg test: 1°, 2° or 3°1×
  • Nitrous acid and the azo-dye test1×

Syllabus preparations

  • Acetanilide and p-nitroacetanilide1×
  • Aniline yellow (p-aminoazobenzene)
  • Mohr's salt and potash alum

Titrimetric analysis

  • Primary standards4×
  • Acid–base indicators5×
  • KMnO₄ vs oxalic acid and Mohr's salt2×

Physical experiments (NTA list)

  • Enthalpy of solution and neutralisation
  • Sols and the iodide–peroxide clock

Also asked here: Purification, Mole concept

  • Key points1

Practise Practical Organic Chemistry next

About 90 past JEE Main questions from this chapter, with instant answer checking and step-by-step solutions where available. Free, and you can start without signing up.

Practise Practical Organic Chemistry

Also free on PrepWiser

Spotted a mistake? Write to support@prepwiser.in and we will fix it in the next version.

Version 1, October 2026. Free to share for study, as it is. Please don't sell it or remove the PrepWiser name.

PractiseSign in to read all 18Download PDF
Free with Google, takes a few seconds10 pages, free