chem (9a despiration)

Question 1

Bromine water test

Answer 1

orange bromine water stays orange with alkanes (C-C single bonds)

becomes clear with alkenes (C=C double bonds)

Question 2

Lucas test

Answer 2

reagent: ZnCl2/HCl

functional group tested: primary, secondary, tertiary alcohols

positive result: cloudy solution initially, then separate layer forms

Question 3

Esterification test

Answer 3

reagent: concentrated H2SO4

function group tested: carboxylic acid, reacting with alcohol

positive result: a fruity odour becomes present (example - pineapple)

Question 4

Similarities

Answer 4

• all include reactions of some sort occurring
• all tests are qualitative forms of testing
• all test for specific functional groups
• lucas test and bromine water test involve halogens as reagents

Question 5

Differences

Answer 5

• esterification test produces an odour change whereas bromine and lucas test produces visual/colour changes
• lucas test determines presence of hydroxyl group where as bromine water test determines double bonds present and esterification test determines presence of carboxylic group
• lucas and esterification test requires catalysts whereas bromine water test does not

Question 6

Limitations - Bromine test

Answer 6

• some compounds may react with the bromine water leading to false positives. for example certain aldehydes
• the test may not determine very low concentration of unsaturated compounds
• the test maybe affected by the presence of other functional groups, which may interfere with the reaction
• doesnt indicate the level of unsaturation

Question 7

Limitations - Lucas test

Answer 7

• this reaction takes time, and secondary and tertiary alcohols react more quickly than primary alcohols, often requiring careful timing for accurate differentiation
• highly concentrated alcohols may not react effectively
• the reaction is sensitive to temperature, which can affect the outcome

Question 8

Limitations - Esterification reaction

Answer 8

• this reaction can establish equilibrium, making it difficult to determine if the reaction has gone to completion
• the presence of impurities can lead to side reactions, producing unwanted by-products
• some reactants or products may not dissolve well in the reaction, affecting the efficiency of the test

Question 9

Overall limitations

Answer 9

• doesn’t tell what position the functional group is in the compound
• doesn’t tell what specific compound is produced