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Qualitative Identification of Functional Groups. Organic Functional Groups Functional group is the site in an organic molecule where a reaction may take.

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Presentation on theme: "Qualitative Identification of Functional Groups. Organic Functional Groups Functional group is the site in an organic molecule where a reaction may take."— Presentation transcript:

1 Qualitative Identification of Functional Groups

2 Organic Functional Groups Functional group is the site in an organic molecule where a reaction may take place. There 10 organic functional groups. Today’s lab will focus on the qualitative identification of alcohols, phenols, aldehydes, ketones, and alkenes.

3 Alkenes - unsaturated

4 Alcohols – primary, secondary and tertiary Phenols

5 Aldehydes and Ketones

6 Tests for alcohols Ceric Ammonium Nitrate – Primary, secondary and tertiary alcohols of up to 10 carbons Chromic Acid – Primary and secondary alcohols, (not tertiary!) Zinc Chloride in HCl (Lucas Test) – Water soluble secondary and tertiary alcohols, (not primary!)

7 Tests for phenols Bromination Ferric Chloride Test for ketones 2,4-Dinitrophenylhydrazine Test

8 Tests for aldehydes Chromic oxide – Aldehydes react in 5 – 15 seconds Tollen’s Test 2,4-Dinitrophenylhydrazine test Test for alkenes Bromination

9 Ceric ammonium nitrate test – Alcohols of up to 10 carbons

10 Chromic Oxide and Sulfuric Acid Primary and Secondary Alcohols

11 Zinc Chloride in HCl (a.k.a Lucas Test) Tests for the presence of secondary and tertiary alcohols only. Low molecular mass alcohols are polar and water soluble. In this reaction they are changed to alkyl halides which are insoluble in water. A positive test will be the presence of an insoluble second layer. Secondary alcohol - solution turns cloudy in 3-5 minutes: Tertiary alcohol - solution turns cloudy immediately, and/or phases separate

12 Tollen’s Test Test for aldehydes Positive test is the appearance of a mirror-like deposit on the test tube. Aldehydes are oxidized to a salt of a carboxylic acid. Plus Ag(s)

13 2,4-Dinitrophenylhydrazine test This is a test for aldehydes and ketones A positive test is the formation of a canary yellow to scarlet precipitate.

14 2,4-Dinitrophenylhydrazine test (for aldehydes)

15 2,4-Dinitrophenylhydrazine test (for ketones)

16 Bromination Test Tests for the presence of a pi bonds. In alkenes and alkynes, no HBr is produced and it is an addition reaction. In the presence of phenol HBr is produced and it is a substitution reaction.

17 Ferric Chloride Test for the presence of a phenol. Positive test is a color change from an orange- yellow to a burgundy color. + 3 HCl


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