Aromatics

• Resonance a way of describing delocalized electrons within certain molecules
• Benzene has six carbon atoms arranged in a ring structure with alternating single and double bonds between them.
• The identity of an organic compound may be determined through qualitative analysis which includes solubility characteristics and functional group tests.
• The solubility of the organic compounds in solvents may provide a general idea of the functional group as well as general characteristic of the sample.
• The flow chart below provides the classifications of different organic compounds:
• After an experiment on four unknown compounds, you record and tabulated your findings.
• The results are as follows:
• Your laboratory professor gave you a setlist of several compounds (structures only) and asked you to do the following:
• Identify the classification of the four unknown compounds.
• Determine the identity of the four unknown compounds.
• Unknown Compound 1 is insoluble in water, soluble in NaOH and soluble in NaHCO 3, according to your results.
• Salicylic acid contains a phenol group, but acetylsalicylic acid does not.
• The acetylsalicylic acid will recrystallize, and the solid impurities (unreacted salicylic acid) should remain dissolved in the solution.
• Iron (III) ion reacts with phenols to form a purple complex.
• Unknown 4 is a primary alcohol with the ability to be oxidized and is soluble in water (only if the carbon atom is less than 4).
• Water is then added to the aspirin solution and it is cooled slowly and then chilled.
• The synthesis of aspirin involves testing the collected aspirin for its purity using FeCl3 (aq).
• If a purple color is observed when FeCl3 is added to an aspirin sample, it indicates the presence of unreacted salicylic acid and the sample is impure.
• Use the solubility flow chart to classify Unknown Compound 1.
• Unknown Compound 2 is water soluble, according to your results.
• Again, refer to the solubility flow chart:
• Unknown Compound 3 is insoluble to all, according to your results.
• Unknown Compound 4 is insoluble to water, soluble in NaOH, insoluble in NaHCO 3, according to your results.
• Unknown Compound 1 is a Strong Acid and is classified as either Carboxylic Acid or Phenol, according to your results.
• Unknown Compound 2 is a low Molecular Weight compound, according to your results.
• Unknown Compound 3 is a neutral compound, may be Alkane, alkyl halide, aromatic hydrocarbon and aryl halides, according to your results.
• Unknown Compound 4 is a Weak Acid and may be phenol or derivatives of phenol, according to your results.
• The identity of Unknown Compound 1 is the Given Compound 6, hexanoic acid.
• These tests include Baeyer’s test, Br 2 test, and sulfuric acid test.
• Hydrocarbons with multiple bonds (unsaturated hydrocarbons except most cycloalkanes) react with bromine to determine the degree of unsaturation.
• The more bromine solution is needed to observe a physical change, the more unsaturated a test sample is.
• Baeyer’s test uses Potassium Permanganate (KMnO4), a very strong oxidizing agent, to oxidize alkenes to geminal diol and alkynes to geminal diketones.
• The purple color of the KMnO4 solution disappears and a precipitate of MnO2 is formed as an indication of a positive test.
• If an unsaturated compound is present, the sample remains colorless (or if colored compound, color remains the same).
• In the presence of light, or at high temperatures, alkanes react with halogens to form alkyl halides.
• Bromine will also react with aromatic compounds, such as phenol, but it can't react with alkanes as they contain only single bonds, and therefore there is no color change when these are mixed.
• Unknown Compound 3 is a neutral compound that may be Alkane, alkyl halide, aromatic hydrocarbon and aryl halides.
• Simple chemical tests can be used to distinguish between these classes.
• Bromine has an orange-brownish color when in solution, so the color of the solution is lost when an alkene or alkyne is present for bromine to react with.
• Reaction with chlorine gives an alkyl chloride.