Unit 4 prac tests

Alkenes test

Bromine water

Brown → Colourless

• Compound is unsaturated C=C

• Nucleophilic addition

Bromine water to alkenes and alkanes

Alkenes

• Bromine → decolourises quickly

• Pi bond reactive

Alkanes

• No reaction (in dark) remain orange

Testing alcohol - ethanoyl chloride

Alcohol + ethanoyl chloride → HCl + Ester

• HCL white steamy fumes

• Ester pleasant fruity smell

• Litmus paper → Red on fumes

• Silver nitrate → white ppt AgCl

Test alcohols PCl₅

Alcohol + phosphorus pentachloride → HCl + POCl₃ + RCL

Confirming HCl

• HCl white fumes - damp litmus paper → red

• Silver nitrate → AgCl

• no fruit smell (no ester)

Test alcohols (esterfication)

Alcohol + Ethanoic acid → Ester + H₂O

• Ethanoic acid + H₂SO₄ Catalyst→ Pour into water

• Pleasant fruity smell

Primary alcohol test

Primary alcohol [O] → Aldehyde + H₂O

Add acidified potassium dichromate Heat and distil

• Orange → Green

• Pungent sharp smell aldehyde

• Distil prevent further oxidation Cr₂​O₇^2-​→Cr³⁺

Secondary alcohol test

Secondary alcohol [O] → Ketone + H₂O

Add acidified potassium dichromate Heat and REFLUX

• Orange → Green

• Ketone odour distilled off immediately

• Distil prevent further oxidation Cr₂​O₇^2-​→Cr³⁺

Tertiary alcohol test

Distil with acidified potassium dichromate and Conc H₂SO₄

• No reaction

Test for phenols

Reagent: iron(III) chloride solution (FeCl₃)

Purple solution formed

• Phenol attached to benzene

Test carboxylic acid

Reagent: Sodium hydrogencarbonate

Fizzing and effervescence colourless gas produced CO2

COOH + NaHCO₃ → COONa + CO₃ + H₂O

Test for carboxylic acid salts

Reagent: Dilute HCl or H₂SO₄

CH₃COO^-Na⁺ + H⁺ → CH₃COOH Vinegar smell (ethanoic acid)

• stronger acid stronger smell

• Butanote → butanoic acid rancid smell

Test aromatic carboxylate salts

Reagent: Dilute HCl or H₂SO₄

White ppt - aromatic acid insoluble

Test for acyl chlorides -COCl

Test: Add few drops to water

COCL + H₃O → COOH + HCl

• Steamy white fumes HCl

Test HCl:

• Damp litmus paper → red

• Silve nitrate → white ppt

Test acyl chlorides (ethanol)

COCL + Alcohol → Ester + HCl

Pleasant fruity smell

White steamy fumes

Test for acid CONH₂

Test: Boil with dilute sodium hydroxide

CONH₂ ​+ OH^-→ COO^- + NH₃​

Ammonia gas → turn damp red litmus → blue

Test for aliphatic amines NH₂ litmus

Test: Damp red litmus Conc HCl

NH₂ + HCl → NH₃ + ​Cl^-

Fishy smell

Red litmus → Blue

Steamy white fumes HCl

Test amine salt

Test: NaOH (Base regenerates amine)

Fishy smell gas

NH₃⁺ + OH^- → NH₂ + H₂O

Test aromatic amines

1. Dissolve dilute HCl

2. Cool 5°C

3. Add Sodium nitrite solution

Observation: Clear solution (no gas if kept cold)

Aromatic NH2 + HNO₂ + HCl → Aromatic N₂Cl^- + 2H₂O

Diazonium salt only stable 0-5°C

Coupling diazonium → Azo dye test

Diazonium salt → Add phenol dissolved in dilute NaOH

Observe: Bright orange red ppt

Test carbonyl compounds

Test: 2,4 DNP

Observe: Yellow orange ppt

Indicate C=O aldehydes and ketones

Tollens reagent

Test: Warm compound with ammoniacal silver nitrate

Observe: Silver mirror

• Only aldehyde positive (stronger reducing agent)

Fehlings solution test

Test: Warm with Fehling’s

Observe: Blue solution → Brick red ppt

• Reduction of copper

Role of ethanol in AgNO₃ test

Haloalkanes are immiscible with water

Ethanol

• Dissolves Allow reaction

Ammonia test after NH₃

AgCl → Dissolves in dilute

AgBr → Dissolves in concentrated

AgI → Does NOT dissolve

Haloalkane test NaOh

1. HYDROLYSIS Gently heat with NaOH (add ethnaol to increase solubility)

2. Add dilute HNO₃ then add AgNO₃

Cl white Br cream I yellow ppt

Test for esters

1. Warm with hydroxylamine + hydrochloride and NaOH

2. Acidify with dilute HCl

3. Add FeCl₃ dropwise

Observe: Deep red purple

COO + NH₂OH → CONHOH

Test methyl ketones

Test: Warm I₂ / NaOH

Observe: Yellow ppt antiseptic smell → Iodoform

• Presence methyl ketones