9. Which two compounds should change to a vibrant yellow, orange or red color wh
ID: 1032290 • Letter: 9
Question
9. Which two compounds should change to a vibrant yellow, orange or red color when reacted with 2,4- DNP A. 2-methyl-2-propanol and 2-butanone B. acetaldehyde and 1-propanol C. 2-methyl-2-propanol and 1-propanol D. acetaldehyde and 2-butanone 10. A student tests an unknown compound with Jones Reagent (chromic acid solution) and 2,4-DNP The unknown gives a blue-green color when tested with the chromic acid solution and produces a vibrant yellow precipitate when tested with 2,4-DNP. What functional group is present in the unknown? A. primary alcohol B. tertiary alcohol C. aldehyde D. ketoneExplanation / Answer
9. 2,4-DNP test is positive for aldehyde and ketone which contains carbonyl group. Among four pairs in options, only option D contains two compounds both of which contains carbonyl group. 2-butanone is a ketone and acetaldehyde is an aldehyde compound, so option D is correct.
10. Jones reagent is an oxidizing agent, which oxidizes alcohol to ketone and aldehyde, and also oxidized aldehyde to carboxylic acid and it changes color to blue-green. But it does not react with ketone. So functional group that give positive test with both Jones reagent and 2,4-DNP is C. aldehyde.
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