Post Lab #4 : Test for Carbonyls: Aldehydes and Ketones Abstract

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Jenny Wang Organic Chemistry II Post Lab #4 :Test For Carbonyls: Aldehydes and Ketones Abstract This lab was about the find the known by doing the quantitative analysis. Before finding out what was the unknown, there were several test had to be done. There were the test of the reaction with 2,4­ Dinitrophenylhydrazine, Tollens’ Test, Fehling’s Test, Iodoform Test and Chromic Acid Test. The unknown #5 was 4­heptanone, based on the results of those tests. This was not a hard lab, but had a lot of new informations involved in it. I learned how to do the quantitative analysis between aldehydes and ketones. Introduction The Laboratory experiment focus on finding the unknown chemical based on those different tests which can eliminate the wrong guess. Both aldehydes and ketones have the carbonyl group, and the two carbon atoms of ketones only bond to carbonyl carbon without the hydrogen, but in the case of aldehydes one of the hydrogen has to bond with the carbonyl carbon. So, those carbonyl group could be aliphatic or part of the aromatic ring because they share carbonyl group. In the reaction with 2,4­ Dinitrophenylhydrazine, all of the 5 test tubes had positive results, both aldehyde and ketone had positive results, all of the test tubes had precipitates. During the Tollen’s Test, the aldehydes was oxidized and reduced silver ion to silver metal . So, the positive test results was aldehydes. In the Fehling’s test, only the aliphatic aldehyde had positive results which showed the red precipitate.In the Iodoform test, only methyl ketones had the yellow precipitates.The last time is Chromic Acid Test, only aldehydes could oxidized by chromic acid, and changed to green color. Experimental procedure(see hand written page) Data and results(include chart) Test Results 2,4­DNPH Tollen’s Test Fehling’s Test TT1: Butanol + + + TT2: Benzaldehyde + + ­ TT3: TT4: Unknown 3­pentanol

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