C. Solubility, lodoform Test, and Benedict\'s Test I. Soluble? 2. lodeform 3. Me

Question

C. Solubility, lodoform Test, and Benedict's Test I. Soluble? 2. lodeform 3. Methy 4. Color S. Oxidation? Ketone Test (yes/no) Propanol Benzaldehyde Acetone Unknowr 6. Identify the unknown as propanal, benzaldehyde, acetone, or cyclohexanone. Give your reasoning Questions and Problems Q1 Indicate the test results for each of the following compounds in the iodoform test and in the Benedict's test: Idoform Test Benedict's Test CH, -C-CH CH CH-CH2-C-CH-CH CH-C-CHCH Copyright 0 2014 Pearson Education, Inc

Explanation / Answer

1. Iodoform test involves the generation of iodoform (CHI3) by the exhaustive iodination of methyl ketones to form a carboxylic acid of the ketone with one carbon less and iodoform. The reaction uses iodine and sodium hydroxide which gives a precipitate of iodoform that is insoluble at room temperature and makes the solution turbid. Thus only methyl ketones answer iodoform test.

Benedict's test uses Benedict's reagent which is a complex mixture of sodium citrate, sodium carbonate and cupric sulphate. When the reagent is treated with aldehydes and ketones, only aldehydes reduce the cupric ion to cuprous oxide while getting oxidised to a carboxylic acid with the former appearing as a red precipitate indicating a positive test. So by this test, aldehydes are distinguished from ketones.

Now of the given compounds, butan-2-one and acetylacetaldehyde will answer iodoform test while acetaldehyde and acetylacetaldehyde answers Benedict's test. Pentan-3-one however does not answer both the tests.

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