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OCR (A) A-Level
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*Revision Materials and Past Papers* 2.1.1 Atomic structure and isotopes 2.1.2 Compounds, formulae and equations 2.1.3 Amount of substance 2.1.4 Acids 2.1.5 Redox 2.2.1 Electron structure 2.2.2 Bonding and structure 3.1.1 Periodicity 3.1.2 Group 2 3.1.3 The halogens 3.1.4 Qualitative analysis 3.2.1 Enthalpy 3.2.2 Reaction Rates 3.2.3 Chemical equilibrium 4.1 Basic concepts and hydrocarbons 4.1.2 Alkanes 4.1.3 Alkenes 4.2.1 Alcohols 4.2.2 Haloalkanes 4.2.3 Organic synthesis 4.2.4 Analytical techniques 5.1.1 How fast? 5.1.2 How far? 5.1.3 Acids, bases and buffers 5.2.1 Lattice enthalpy 5.2.2 Enthalpy and entropy 5.2.3 Redox and electrode potentials 5.3.1 Transition elements 5.3.2 Qualitative analysis 6.1.1 Aromatic compounds 6.1.2 Carbonyl compounds 6.1.3 Carboxylic acids and esters 6.2.1 Amines 6.2.2 Amino acids, amides and chirality 6.2.3 Polyesters and polyamides 6.2.4 Carbon–carbon bond formation 6.2.5 Organic synthesis 6.3.1 Chromatography and qualitative analysis 6.3.2 Spectroscopy Required Practicals

Required Practicals

1 Moles determination 2 Acid–base titration 3 Enthalpy determination 4 Qualitative analysis of ions 5 Synthesis of an organic liquid 6 Synthesis of an organic solid 7 Qualitative analysis of organic functional groups 8 Electrochemical cells 9 Rates of reaction – continuous monitoring method 10 Rates of reaction – initial rates method 11 pH measurement 12 Research skills

Core Practical 7: Qualitative Analysis of Organic Functional Groups

Aim: Use of apparatus for qualitative tests for organic functional groups.

Note: When heating organic compounds, use an electric heater or water bath. Organic compounds are often volatile and flammable, so they must be kept away from naked flames (such as a Bunsen burner).

Functional Group Tests (Test-Tube Scale)

These qualitative tests help identify the presence of functional groups in organic molecules:

Alkenes

Test: Add bromine water

OCR (A) Chemistry test for alkenes using bromine water turning from orange to colourless.

Positive result: Orange → colourless (electrophilic addition to C=C)

Haloalkanes

Test: Add ethanolic AgNO₃ and warm

OCR (A) Chemistry test for haloalkanes using AgNO3 in ethanol.

Result: Precipitate forms
Cl⁻: white
Br⁻: cream
I⁻: yellow

Phenols

Test 1: React with NaOH → dissolves (acid–base reaction)

OCR (A) Chemistry reaction of phenol with sodium hydroxide.

Test 2: React with Na₂CO₃ → no reaction (unlike carboxylic acids)

Carbonyl Compounds (Aldehydes or Ketones)

Test: Add 2,4-DNP (Brady’s reagent)

OCR (A) Chemistry test for carbonyl groups with 2,4-DNP showing orange precipitate.

Result: Orange/yellow precipitate of a 2,4-dinitrophenylhydrazone derivative

Aldehydes

Test: Add Tollens’ reagent (ammoniacal silver nitrate), warm gently

OCR (A) Chemistry Tollens' reagent test for aldehydes producing a silver mirror.

Positive result: Silver mirror on test tube walls

Primary or Secondary Alcohols and Aldehydes

Test: Add acidified potassium dichromate (K₂Cr₂O₇/H₂SO₄)

OCR (A) Chemistry test using acidified dichromate for alcohols and aldehydes turning from orange to green.

Result: Orange → green (Cr⁶⁺ reduced to Cr³⁺). Aldehydes and 1°/2° alcohols oxidised.

Carboxylic Acids

Test: Add Na₂CO₃ or NaHCO₃

OCR (A) Chemistry test for carboxylic acids with sodium carbonate showing effervescence.

Result: Effervescence (CO₂ gas evolved). Confirm with limewater test: CO₂ turns limewater cloudy.