Answer:
a) The reagent used to test for the presence of a primary/secondary alcohol is acidified potassium dichromate solution. The chemical formula for acidified potassium dichromate is K2Cr2O7 + H2SO4.
b) The colour change observed when acidified potassium dichromate reacts with an alcohol is from orange to green.
c) The oxidation of a primary alcohol produces an aldehyde or a carboxylic acid, depending on the conditions.
d) The oxidation of a secondary alcohol produces a ketone.
e) The dichromate test does not work for tertiary alcohols such as methylpropan-2-ol because tertiary alcohols cannot be oxidized further. The chemical structure of methylpropan-2-ol is CH3-C(CH3)(OH)-CH3, which has a tertiary carbon atom (the carbon atom with three alkyl groups attached).
a) A simple chemical test for the presence of a carboxylic acid group in a molecule is the reaction with sodium hydrogencarbonate (NaHCO3). When a carboxylic acid reacts with NaHCO3, it produces carbon dioxide gas, which can be detected by effervescence or the formation of bubbles.
Reagent: Sodium hydrogencarbonate (NaHCO3)
Observation: Effervescence or the formation of bubbles would confirm the gas produced in this test is carbon dioxide.
b) For a completely unknown compound, the hydrogencarbonate test is not conclusive proof that a carboxylic acid group is present because other functional groups such as phenols and aldehydes can also produce carbon dioxide gas upon reaction with NaHCO3. Therefore, additional tests are required to confirm the presence of a carboxylic acid group, such as the use of litmus paper to test for acidity or the reaction with a carboxylic acid derivative such as an ester or an acid chloride.