Qualitative Tests for Hydrocarbons PDF

De La Salle University - Dasmariñas Qualitative Tests for Hydrocarbons Presented by Group 1 (MEB11) Inorganic and Organic Chemistry Laboratory Group 1 Denzel Patricia Vherong Alcayaga Agapito Andres Mia Arguelles Chelsea Baria Group Leader  Introduction Hydrocarbons, com...

De La Salle University - Dasmariñas Qualitative Tests for Hydrocarbons Presented by Group 1 (MEB11) Inorganic and Organic Chemistry Laboratory Group 1 Denzel Patricia Vherong Alcayaga Agapito Andres Mia Arguelles Chelsea Baria Group Leader  Introduction Hydrocarbons, composed of carbon and hydrogen, are classified as alkanes, alkenes, alkynes, or aromatic hydrocarbons. This experiment generates ethyne (an alkyne) and uses other reagents, together with various qualitative tests to classify hydrocarbons: 1. Baeyer’s Test: Identifies unsaturated hydrocarbons via color change. 2. Br2 Test: Detects unsaturated hydrocarbons by decolorizing bromine. 3. Sulfuric Acid Test: Reacts with unsaturated hydrocarbons. 4. Tollens’ Test: Differentiates aldehydes (silver mirror) from ketones (detects terminal alkynes). 5. Friedel-Crafts Reaction: Confirms aromatic hydrocarbons. The tests analyze physical properties like color changes and solubility to determine hydrocarbon types.  Materials Reagents: Equipments: Calcium Carbide(CaC2) Conical Flask Distilled Water Test tubes and holders Acidified copper(II) sulfate solution Dropper Potassium permangranate (KMnO4) Lighted Paper Bromine in dichloromethane (DCM) Water bath setup Concentrated sulfuric acid (H2SO4) Silver nitrate (AgNO3) Ammonium Hydroxide (NH4OH) Benzene Aluminum Chloride (AlCl3) Methodology Generation, Collection, and Testing of Ethyne Gas 1. Calcium carbide (CaC2) reacted with distilled water. 2. Gas purified using acidified copper(II) sulfate solution. 3. Collected in test tubes submerged in water for safety. 4. Tested flammability using a lighted taper.  Methodology Experiment Proper: 4 Qualitative Tests 1. Baeyer’s test: KMnO4 added to samples; product observed 2. Br2 test: Bromine in DCM added; product observed. 3. Sulfuric Acid: H2SO4 added to samples; product observed. 4. Tollens’ test: 5% AgNO and NH4OH mixture used; product observed. Additional Test: Friedel-Crafts Reaction: Benzene and AlCl3 combined in DCM; product observed. Experiment Results ACTUAL RESULTS, DATA PRESENTATION, AND CONCLUSION Flammability Test for Ethyne A luminous, smoky flame with soot was formed. Confirmed the presence of ethyne.  Observations Results Tollens’ Baeyer’s Sulfruic Test Friedel- Reagent Base Test Br2 Test Acid Test (AgNO3 Crafts Observations of Physical form (KMn)4) (H2SO4) + NH4OH) Reaction Properties of the Reagents under Qualitative Tests Layering of Cloudy white Colorless liquids;Reddish- Dark orange Clear liquid - liquid; Precipitate Cyclohexane pink KMnO4 formed at the liquid settled at the liquid bottom bottom Layering of Colorless Orange Cloudy white liquid; Hexane - The table depicts all qualitative liquids;Reddish-pink KMnO4 settled at the Clear liquid Precipitate formed liquid bottom liquid at the bottom Layering of Cloudy white observations obtained throughout the Colorless liquids;Reddish- Dark orange liquid; - experiment. The first and second columns liquid; Precipitate Heptane pink KMnO4 Precipitate formed Clear liquid formed at the liquid settled at the at the bottom bottom bottom show the reagents used and their initial Cloudy white liquid; Colorless forms prior to testing, respectively. The Light orange Brown liquid Some precipitate Ethyne gas formed liquid formed Clear liquid formed at the bottom, some floated - third to sixth columns show the results of White, Orange Clear liquid, Cloudy white liquid; each reagent with the four qualitative Crystallization; Solids Naphthalene crystalline solid (powder-like) clumped with slight reddish-pink color liquid some solids floating Colloidal precipitate formed throughout solution - Light brownish - tests. Clear, light orange bubbles Layering of liquids; Cloudy white liquid; - Clear liquid at top, Light Corn Oil brownish- settled at the bottom yellow liquid settled at the bottom Clear liquid Colloidal precipitate formed yellow liquid throughout solution White crystalline Colorless - - - - precipitate Benzene formed at the liquid bottom Base Form of Reagents: Cyclohexane Hexane Heptane Ethyne Naphthalene Corn oil Benzene  Results Reagent Result Indication Results of Baeyer’s Test Cyclohexane Negative Alkane/Aromatic Hexane Negative Alkane/Aromatic Potassium permanganate (KMnO₄) reacts with unsaturated hydrocarbons. Heptane Negative Alkane/Aromatic Positive Reaction: Pink to Brown = alkene or alkyne Ethyne Positive Alkene/Alkyne Negative Reaction: Naphthalene Negative Alkane/Aromatic Retains the Pink color = alkane or aromatic Partially Sample may contain unsaturated compounds Corn Oil (Alkene/Akyne) Positive  Results Reagent Result Indication Results of Br2 Test Cyclohexane Negative Alkane/Aromatic Bromine in dichloromethane (DCM) Hexane Negative Alkane/Aromatic detects unsaturated hydrocarbons. Positive Reaction: Heptane Negative Alkane/Aromatic Orangeish-Brown to Clear / Slight yellow = alkene or alkyne Ethyne Negative Alkane/Aromatic Negative Reaction: Naphthalene Negative Alkane/Aromatic Retains the Orangeish-Brown color = alkane or aromatic Partially Sample may contain unsaturated compounds Corn Oil (Alkene/Akyne) Positive  Results Reagent Result Indication Results of Sulfuric Acid Test Cyclohexane Negative Chemical is not an alkene Concentrated Sulfuric Acid (H2SO4) reacts with unsaturated hydrocarbons Hexane Negative Chemical is not an alkene (alkene). Positive Reaction: Heptane Negative Chemical is not an alkene Exothermic change (heat) or Darkening of color Ethyne Negative Chemical is not an alkene = alkene Negative Reaction: Naphthalene Negative Chemical is not an alkene No change in temperature or Retains the colorless appearance = alkane or aromatic Corn Oil Negative Chemical is not an alkene  Results Reagent Result Indication Results of Tollens’ Test Cyclohexane Negative Chemical is not an alkyne Tollens’ reagent, a mixture of silver nitrate (AgNO3) and ammonium Hexane Negative Chemical is not an alkyne hydroxide (NH4O4), detects terminal alkynes. Heptane Negative Chemical is not an alkyne Positive Reaction: Silver-mirror compound = terminal alkyne Ethyne Positive Chemical is an alkyne Negative Reaction: Naphthalene Negative Chemical is not an alkyne No silver-mirror compound formed = not an alkyne Corn Oil Negative Chemical is not an alkyne  Results Results of Friedel- Reagent Result Classifica Crafts Reaction tion Aluminum chloride (AlCl3) in DCM reacts with aromatic hydrocarbons. Positive Reaction: White crystalline precipitate = aromatic hyrdrocarbon Benzene Positive Aromatic Negative Reaction: No white crystalline precipitate formed = not an aromatic hydrocarbon  Conclusion Reagent Classification These reagents were classified based on the qualitative tests Cyclohexane Alkane utilized. Cyclohexane, hexane, & heptane - alkanes Hexane Alkane Produced negative reactions to qualitative tests that detect double or triple bonds Ethyne - alkyne Heptane Alkane Positive Baeyer’s Test Positive Tollens’ Test Ethyne Alkyne Naphthalene - aromatic Unreactive in all tests Naphthalene Aromatic Corn Oil - alkane/alkene/alkyne/aromatic Partial reactions, if not negative, to all qualitative tests Corn Oil Alkane/Alkene/Alkyne/Aromatic Benzene - aromatic Friedel-Crafts test Benzene Aromatic