Post-Laboratory A4 - Characteristic Reactions of Hydrocarbons 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 Post-Lab Discussion: Characteristic Reactions of Hydrocarbons Inorganic and Organic Chemistry Laboratory Unit Intended Learning Outcome: At the end of the unit, the student must be able to differentiate hydrocarbons in terms of: a. intrinsic physical properties; b. chemical properties, structure, and behavior characterize hydrocarbons based on: a. flammability; b. active unsaturation; c. aromaticity Topic Outline ❖ Physical Characteristics ❖ Solubility in Concentrated H2SO4 ❖ Ignition Test ❖ Test for Active Unsaturation Baeyer’s Test Bromine Test ❖ Test for Aromaticity: Nitration Test ❖ Test for Basic Oxidation  UST General Santos Properties of Hydrocarbons Characteristic Reactions of Hydrocarbons UST General Santos Hydrocarbons Aliphatic Aromatic Acyclic Cyclic Cyclic Planar Conjugated Alkanes Cycloalkanes Alkenes Cycloalkenes Alkynes Cycloalkynes UST General Santos Classify! Hexane Toluene Benzene A. Physical Characteristics Describe the physical appearance of the sample at room temperature. Hexane Toluene Benzene 5 drops of the sample Physical Colorless Colorless Colorless Appearance Liquid Liquid Liquid *if sample has not evaporated after 15 minutes, describe the sample as “non-volatile” VOLATILE SUBSTANCE - readily evaporates at room temperature because of high vapor pressure Vapor pressure - pressure exerted by a vapor above a liquid when the liquid and vapor are in physical equilibrium with each other attractive forces : vapor pressure : volatile B. Solubility in Concentrated H2SO4 Describe the solubility/reaction of the sample in concentrated H2SO4 10-15 drops 1 drop of Conc H2SO4 of the sample Hexane Toluene Benzene Solubility Insoluble Insoluble Insoluble Solubility - maximum amount of solute that will dissolve in a given amount of solvent under a given set of conditions POLARITY organic compounds are generally NON-POLAR sulfuric acid is POLAR “like dissolves like” C. Ignition Test Describe the flame/residue of the sample. Hexane Toluene Benzene Flame Clean Luminous with Luminous with Luminous Black Smoke Black Smoke Residue None Black Black 5 drops of the sample Combustion - reaction between a substance and oxygen (usually from air) that proceeds with the evolution of heat and light - can occur completely or incompletely CxHx + O2 CO2 + H2O + Heat Energy  COMPLETE INCOMPLETE Combustion Combustion CxHx + O2 CO2 + H2O CxHx + O2 CO + CO2 + c + H2O C:H ratio, luminosity, soot Degree of Luminosity aromatic compounds > unsaturated hydrocarbons > saturated hydrocarbons TEST FOR ACTIVE UNSATURATION - immediate reaction to halogenating substances such as the diatomic halogen compounds (Br2, CL2, I2, F2) - easily oxidized to hydroxy alkanes Tests for active unsaturation - baeyer’s test - bromine test D. Test for Active Unsaturation: Baeyer’s Test Record the extent and rate of color change Hexane Toluene Benzene Color Change None (+) brown (+) brown 5 drops 2 drops of the sample of 2% KMnO4 Baeyer's Test - aqueous KMnO4 solution - redox reaction - oxidation of alkenes - alkenes → alkanediol Baeyer's Test NEGATIVE POSITIVE alkanes alkenes, alkyne, aromatics Baeyer's Test VDGEROA - valence of an element decreases that means it gained electrons, it was reduced and its compound is the oxidizing agent - potassium permanganate (purple) to manganese dioxide (brown) VILEORA - valence of an element increases that means it loss electron, it was oxidized and its compound acts as the reducing agent D. Test for Active Unsaturation: Bromine Test Record the extent and rate of color change Hexane Toluene Benzene Color Change None Colorless Colorless Inference Not actively Unsaturated Unsaturated unsaturated 5 drops 10 drops of the sample of 0.5% CCl4 Bromine Test - Br2 in dichloromethane solution - decoloration Positive: alkenes and alkynes unsaturation, bromine needed, color Bromine Test NEGATIVE POSITIVE alkanes alkenes, alkyne, aromatics E. Test For Aromaticity: Nitration Test Record observation Hexane Toluene Benzene Observation None (+) Yellow (+) Yellow Oily Layer Oily Layer Inference Aliphatic Aromatic Aromatic 5 drops 8 drops 20 drops of the sample nitrating mixture water Nitration Test - introduces a nitro group into an aromatic ring - positive for aromatic hydrocarbons  5 drops sample F. Test for Basic Oxidation Record the extent and rate of color change 8 drops 2% KMnO4 Hexane Toluene Benzene 3 drops Color Change None (+) Bluish None 10% NaOH (aq) Black Precipitate Inference Not an Arene Not an Arene Arene Basic Oxidation Test - test for arenes (alkylbenzene) - oxidation of alkyl group to COOH  UST General Santos Post-Lab Discussion: Characteristic Reactions of Hydrocarbons 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.