A5 (Pre) - Classification Tests for Hydroxyl- and Carbonyl-containing Compounds PDF

PRAYER BEFORE CLASS Holy Spirit, Divine Creator, true source of light and fountain of wisdom! Pour forth your brilliance upon my dense intellect, dissipate the darkness which covers me, that of sin and of ignorance. Grant me a penetrating mind to understand, a retentive memory, method and ease of le...

PRAYER BEFORE CLASS Holy Spirit, Divine Creator, true source of light and fountain of wisdom! Pour forth your brilliance upon my dense intellect, dissipate the darkness which covers me, that of sin and of ignorance. Grant me a penetrating mind to understand, a retentive memory, method and ease of learning, the lucidity to comprehend, and abundant grace in expressing myself. Guide the beginning of my work, direct its progress and bring it to successful completion. This I ask through Jesus Christ, true God, and true man, living and reigning with You and the Father, forever and ever. Amen.  UST General Santos Activity 4: Classification Tests for Hydroxyl- and Carbonyl- containing Compounds Inorganic and Organic Chemistry Laboratory Unit Intended Learning Outcome: At the end of the unit, the student must be able to: ❖ distinguish whether a compound is hydroxyl- or carbonyl- containing; ❖ differentiate the three types of alcohols; ❖ differentiate aldehydes from ketones; ❖ illustrate the chemical equations involved in the different reactions; and ❖ explain the mechanisms involved in the differentiating tests. Topic Outline ❖ Properties ⮚ Alcohol ⮚ Ketones ⮚ Aldehydes ❖ Laboratory Procedures ⮚ Solubility of Alcohols in Water ⮚ Ester Formation ⮚ Lucas Test ⮚ Oxidation of Alcohols using Acidic Potassium Dichromate ⮚ 2,4-Dinitrophenylhydrazine Test ⮚ Fehling’s Test ⮚ Tollens’ Silver Mirror Test ⮚ Iodoform Test  UST General Santos Properties of Alcohol Classification Tests for Hydroxyl- and Carbonyl-containing Compounds Physical Properties of Alcohols - depend on whether the polar or nonpolar portion of its structure dominates - Determining factors: - Length of the nonpolar carbon chain - Number of polar hydroxyl groups Physical Properties of Alcohols Boiling Point BOILING POINT as length of carbon chain increases as number of hydroxyl group increases Physical Properties of Alcohols Water Solubility - as carbon chain increases beyond three (3) carbons, solubility in water rapidly decreases Chemical Properties of Alcohols Combustion - reaction between a substance and oxygen (usually from air) Alcohol + O2 CO2 + Water Chemical Properties of Alcohols Intramolecular Alcohol Dehydration dehydration reaction - chemical reaction in which the components of water are removed from a single reactant or from two reactants (H from one reactant and OH from the other) - in intramolecular dehydration, both water components are removed from the same molecule reaction conditions: 1. temperature of 180 degree celsius 2. presence of sulfuric acid (catalyst) Alcohol Alkene Chemical Properties of Alcohols Intramolecular Alcohol Dehydration Chemical Properties of Alcohols Intramolecular Alcohol Dehydration elimination reaction - reaction in which two groups or two atoms on neighboring carbon atoms are removed or eliminated from a molecule, leaving a multiple bond between carbon atoms Alcohol Alkene Chemical Properties of Alcohols Intermolecular Alcohol Dehydration - at lower temperature (140 degree celsius), an intermolecular process occur to produce a ether (a compound with the general structure R-O-R) Alcohol Ether Chemical Properties of Alcohols Intermolecular Alcohol Dehydration condensation reaction - reaction in which two molecules combine to form a larger one while liberating a small molecule, usually water Chemical Properties of Alcohols Oxidation set of operational rules for organic redox: 1. an organic oxidation is an oxidation that increases the number of C-O bonds and/or decreases the number of C-H bonds 2. an organic reduction is an oxidation that decreases the number of C-O bonds and/or increases the number of C-H bonds Chemical Properties of Alcohols Oxidation - primary and secondary alcohols readily undergo oxidation in the presence of mild oxidizing agents oxidizing agents: - potassium permanganate - potassium dichromate - chromic acid Chemical Properties of Alcohols Oxidation Chemical Properties of Alcohols Oxidation Chemical Properties of Alcohols Oxidation Chemical Properties of Alcohols Oxidation Chemical Properties of Alcohols Halogenation - halogen atom is substituted for the hydroxyl group, producing alkyl halide source of halogen atoms: 1. PBr3 2. PCl3 HEAT is required Alcohol Alkyl Halide  UST General Santos Properties of Aldehydes and Ketones Classification Tests for Hydroxyl- and Carbonyl-containing Compounds Physical Properties of Aldehydes and Ketones C1 and C2 Aldehydes - gases at room temperature C3-C11 Straight-chain Saturated Aldehydes - liquids at room temperature >C11 Aldehydes - solids at room temperature Lower molecular mass ketones - colorless liquids at room temperature Physical Properties of Aldehydes and Ketones Boiling Point intermediate between alcohols and alkanes of similar molecular mass aldehydes and ketones have higher boiling points than alkanes aldehydes and ketones have lower boiling points than the corresponding alcohols LOWERS BOILING POINT - presence of alkyl groups - presence of unsaturation in the carbon chain Physical Properties of Aldehydes and Ketones Water Solubility - aldehyde and ketones having fewer than six (6) carbon atoms are soluble both in organic solvents and water - six (6) or more carbon atoms are present, they are soluble in organic solvent but not in water Physical Properties of Aldehydes and Ketones Odor - low molecular mass aldehydes: pungent, penetrating, unpleasant odors - higher molecular mass aldehydes (above C8): fragrant - ketones: pleasant odors Chemical Properties of Aldehydes and Ketones Oxidation Oxidizing agents: oxygen in air, potassium dichromate, tollens’ test, benedict’s test Chemical Properties of Aldehydes and Ketones Oxidation Oxidizing agents: oxygen in air, potassium dichromate, tollens’ test, benedict’s test Chemical Properties of Aldehydes and Ketones Reduction Reducing agent: hydrogen gas Chemical Properties of Aldehydes and Ketones Reaction of Aldehydes and Ketones with Alcohols Chemical Properties of Aldehydes and Ketones Hemiacetal Formation - addition reaction in which a molecule of alcohol adds to the carbonyl group of an aldehyde or ketone hemiacetal - an organic compound in which a carbon atom is bonded to both a hydroxyl group (-OH) and an alkoxy group (-OR) Chemical Properties of Aldehydes and Ketones Acetal Formation - condensation reaction - reaction of hemiacetal with a secondary alcohol molecule Acetal - an organic compound in which a carbon atom is bonded to two alkoxy groups (-OR)  UST General Santos Procedures Characteristic Reactions of Hydrocarbons Instructions ❖ Please refer to pages 55-60 for the materials needed and specific procedure of the activity. Materials needed ❖ 250 mL beakers ❖ Test tubes ❖ Test tubes with screw cap ❖ Pipettes ❖ Hot plate ❖ Colorless vials ❖ Test tube holder ❖ Test tube brush ❖ Spatula ❖ Glass dropper  10 drops A.Solubility of Alcohols in Water of each alcohol sample 1. Place 10 drops of each alcohol sample into 1 mL separate test tubes distilled water 2. Add 1 mL of distilled water dropwise to each test tube, shake the mixture thoroughly after each addition 3. If a cloudiness results, continue adding distilled water 10 drops at a time with vigorous shaking until it produces a homogenous dispersion *take note of the total volume of distilled water added 4. If a no cloudiness results after step #2, the alcohol is miscible with water 5. Note down the results B. Ester Formation CARBOXYLIC ACID ALCOHOL ODOR Formic Acid Ethyl Alcohol Rum Acetic Acid Ethyl Alcohol Fruity Acetic Acid Isopentyl Alcohol Banana Acetic Acid Octyl Alcohol Orange Propionic Acid Ethyl Alcohol Pineapple B. Ester Formation 1. Into the appropriate test tube, place 10 drops of carboxylic acid and 10 drops of alcohol then add 4 drops of conc. sulfuric acid 10 drops 10 drops 4 drops carboxylic acid alcohol conc. H2SO4 B. Ester Formation 2. Pour about 150 mL of tap water into 250 mL beaker 3. Place the test tube in the beaker containing the tap water and heat the water on a hot plate to a temperature of about 60 degree celsius. Leave the test tube in the water bath for 15 mins. 4. Cool the test tube by immersing in cold water in another beaker B. Ester Formation 5. Add 5 mL of distilled water to the test tube *carefully note the odor of the ester formed by holding the test tube about 30 cm away from your nose and gently waft the vapor towards your nose without inhaling deeply. compare observed odor from odor of the ester provided in the table 5 mL 10 drops 10 drops 4 drops distilled water carboxylic acid alcohol conc. H2SO4 C. Lucas Test Preparation of Lucas reagent: Measure 47 mL of conc. HCl and pour it into a 250-mL beaker. Place the beaker in an ice bath. Add the accurately weighed 6.25 g of anhydrous ZnCl, to the conc. HCl in the beaker slowly. Stir the mixture until the ZnCl2 dissolves completely. Store the reagent in a cool dry place for later use. PRECAUTION: Conc. HCl is CORROSIVE and can irritate the skin. ZnCL2 is HIGHLY CORROSIVE and may cause damage to the SKIN and RESPIRATORY SYSTEM. Please handle the reagents with care.  2-3 drops each alcohol C. Lucas Test 1. Place about 2-3 drops of each alcohol 1 mL in separate test tubes with screw cap lucas reagent 2. Add 1 mL of the lucas reagent. 3. Cap the test tube and shake vigorously for a few seconds 4. Allow to stand at room temperature 5. Observe the rate of formation of the cloudy suspension or formation of 2 layers D. Oxidation of Alcohols using Acidic Potassium Dichromate Preparation of Acidic Potassium Dichromate: Dissolve 3g of K2Cr2O7 in 80 mL distilled water and slowly, with stirring and cooling, add 10 mL of conc. H2SO4 to the solution. The reagent should be prepared fresh each time. PRECAUTION: Acidic K2CR2O7 is TOXIC and CORROSIVE D. Oxidation of Alcohols using Acidic Potassium Dichromate 1. Place 2 drops of each sample into separate test tubes 2. Add 5 drops of acidic K2CR2O7 solution, one drop at a time, while shaking the mixture 2 drops 5 drops each sample acidic K2CR2O7 D. Oxidation of Alcohols using Acidic Potassium Dichromate 3. Pour about 150 mL of tap water into 250 mL beaker 4. Place the test tubes in the beaker containing the tap water and heat the water on a hot plate to a temperature of about 60 degree celsius. Leave the test tubes in the water bath for 5 mins. 5. Note the color of each solution E. 2,4-Dinitrophenylhydrazine Test Preparation of DNP reagent: Dissolve 3 g of 2,4-dinitrophenylhydrazine in 15 mL of conc. H2SO4. Then slowly add this solution with stirring to a mixture of 20 mL water in 75 mL of 95% ethanol. Stir and filter. E. 2,4-Dinitrophenylhydrazine Test 1. Place 2 drop of each sample into separate test tubes 2. Add 3 drops of DNP reagent. Shake well. If no yellow or orange or orange-red precipitate forms, allow the solution to stand for at least 15 mins. Record observations. 2 drops 3 drops each sample DNP reagent F. Fehling’s Test Preparation of Fehling’s reagent: Fehling’s A: 7 g of copper sulfate pentahydrate dissolved in 100 mL distilled water Fehling’s B: 35 g of potassium sodium tartrate and 10 g of NaOH in 100 mL distilled water Mix two equal parts of Fehling’s A and Fehling’s B before use to prepare the Fehling’s reagent F. Fehling’s Test 1. Prepare four test tubes with 1 mL of freshly prepared Fehling’s reagent 2. Add 3 drops each of the samples 1 mL freshly 3 drops prepared each sample fehling’s reagent F. Fehling’s Test 3. Place the tubes in a beaker of boiling water and observe changes which occur during 10-15 mins 4. Avoid excessive heating 5. Record observation G. Tollens’ Silver Mirror Test Preparation of Tollen’s reagent: Mix thoroughly 2 mL of 5% AgNO3 solution and 2 drops 5% NaOH. The add, drop by drop and with constant stirring, 2% NH4OH to dissolve the precipitate. The test will not work properly upon addition of excess ammonia.  10 drops of each alcohol sample G. Tollens’ Silver Mirror Test 1 mL 1. Prepare four test tubes with 1 mL of freshly distilled water prepared Tollens’ reagent 2. Add 2 drops each of the samples separately on each test tube 3. Shake the mixture. Allow it to stand for 10 minutes 4. If no reaction has occurred, place the test tube in a beaker of warm water (35-50 degree celsius) for 5 mins 5. Record observations WASTE DISPOSAL: DO NOT store unused reagent. If Tollen’s reagent is left unused for a period of time, it may form EXPLOSIVE SILVER. TO AVOID this, NEUTRALIZE unused reagent with a little NITRIC ACID and discard. H. Iodoform Test 1. Place 2 drops of each sample into separate test tubes 2. Add 20 drops 10% KI solution 3. Add slowly, while shaking, 20 drops of fresh NaOCl to each test tube and mix 4. Note for the formation of yellow precipitate 2 drop 20 drops each sample NaOCl  UST General Santos Activity 4: Classification Tests for Hydroxyl- and Carbonyl- containing Compounds Inorganic and Organic Chemistry Laboratory References ❖ Bettelheim, F. A, W. H., Brown, M. K. Campbell, S. O. Farrell & O. Torres. (2021). Introduction to General, Organic and Biochemistry, 12th ed. Boston, MA, USA: Cengage Learning End of discussion Do you have any questions? PRAYER AFTER CLASS Grant me, O Lord my God, a mind to know you, a heart to seek you, wisdom to find you, conduct pleasing to you, faithful perseverance in waiting for you, and a hope of finally embracing you, Amen.