Topic 14 - Qualitative Tests for Functional Groups (specific test)

Question 1

Bromine Water Test

Answer 1

Testing for: Carbon-to-Carbon double bond

Type of reaction: addition

Reactant: Br2

Product: dibromoalkane

Observation: Loss of brownish-red colour

Question 2

Degree of Unsaturation (Iodine) Test

Answer 2

Testing for: Carbon-to-Carbon double bond

Type of reaction: addition

Reactant: I2

Product: dibromoalkane

Observation: Loss of dark red/yellow/orange colour

Note: can also be used to calculate the amount of double bonds present using stoich

Question 3

Baeyers Test

Answer 3

Testing for: Carbon-to-Carbon double bond

Type of reaction: oxidation (check)

Reactant: MnO4- + H2O (remember to balance)

Product: dihydroxyl (glycole) + OH- + MnO2

Observation: purple (MnO4-) -> brown-black (MnO2)

Note: can also be used to calculate the amount of double bonds present using stoich

Question 4

Esterification

Answer 4

Testing for: -OH and -COOH

Type of reaction: esterification

Reactant: alcohol + carboxylic acid

Product: ester + H2O

Observation: pleasant aroma (fruity or floral)

Note: requires catalyst of H2SO4 (l, concentrated) and heat

Question 5

Oxidation reaction

Answer 5

Testing for: -OH

Type of reaction: oxidation

Reactant: alcohol (primary, secondary)

Product:
- primary alcohol: aldehyde (partial oxidation), carboxylic acid (full)
- secondary: ketone

Observation: colour change (KMnO4 purple -> clear. K2Cr2O7 orange -> green)

Note: requires catalyst of KMnO4 or K2Cr2O7 and heat for full oxidation of primary alcohol. Tertiary alcohols cannot oxidise.

Question 6

Test with bases

Answer 6

Testing for: -COOH

Type of reaction: ?

Reactant: base (NaCO3, sodium carbonate)

Product: CO2 + H2O + salt (Na+ replaces H on carboyxl group)

Observation: CO2 gas produced

Note: you can use other bases with hydroxides but they will only produce salt and water (no CO2) and thus may be harder to observe.

Question 7

pH test/litmus paper

Answer 7

Testing for: -COOH

Type of reaction: ?

Reactant: sample (doesn’t have to be carboyxlic acid)

Product: N/A

Observation: color change (universal indicator turns red/orange/yelllow in acidic conditions. Blue litmus paper turns red in acidic conditions)

Note: can’t differentiate between what kinds of acids