DAT High Yield Organic Chemistry Lab Techniques and Lab Tests Questions And Well Defined Answers Graded A+

Extraction - correct answer Separates dissolved subs. Based on differential solubility in aqueous vs. organic solvents Water = aqueous layer; ether = organic layer Like dissolves like 3 IMF that affects solubility o hydrogen bonding - ex. Alcohols & acids will move into aq. layer o dipole-dipole interactions - less likely to move in aq. layer o van der Waals (London dispersion) = nonpolar molecules (does not go into aq. layer) when ACID dissociates, resulting anion formed is more soluble ***ADDing a BASE helps EXTRACT ACID into the aq. layer Filtration - correct answer separates solids from liquids Recrystallization - correct answer Separates solids based on diff. solubilities; temperature is important Sublimation - correct answer Separates solids based on their ability to sublime Centrifugation - correct answer Separates large things (ex. Cells, organelles, macromolecules) based on mass and density Distillation - correct answer Separates liquids based on boiling point (depends on intermolecular forces) Chromatography - correct answer Uses stationary and mobile phases to separate compounds based on how tightly they adhere (generally due to polarity, but sometimes size as well) Electrophoresis - correct answer Used to separate biological macromolecules (such as proteins or nucleic acids) based on size and sometimes charge. Separates macromolecules based on isolectric point -If pH = isoelectric point protein doesn't move -If pH isoelectric point protein deprotonated Simple Distillation - correct answer separate liquids that boil BELOW 150OC (at least 25C apart) Vacuum Distillation - correct answer separates liquids that boil ABOVE 150C - reduced P, lowering the BP of liquids (preventing their decomposition typical at high T) Fractional Distillation - correct answer separates liquids that boil LESS than 25C apart - near the top of the column, vapor is composed solely of 1 component, which will condense and collect in the receiving flask -can be thought of as repeated distillation of same vapor thin layer chromatography - correct answer used to isolate individual compounds from a complex mixture - stationary phase (solid medium) & mobile phase (liquid) - diff. compounds will adhere to stationary phase w/ diff. strengths o POLAR compounds bound TIGHTly to the silica gel - eluting poorly into the less polar solvent - Rf = dist. compound / dist. of solvent - Reverse phase chromatography - very nonpolar stationary phase instead of silica gel SDS & Agorose Gel Electrophoresis - correct answer separates molecules based on size Boiling point trends - correct answer increases with chain length due to dispersion forces; decreases with branching Melting point trends - correct answer increases with branching because the molecules can pack tightly and with chain length due to dispersion forces Tollen's test (silver mirror test) - correct answer Regeants used: Ag2O / NH3 or Ag(NH3)2+ Functional Groups tested: Aldehydes Positive Results: Sides of flask are coated with a silver mirror Iodoform Test - correct answer Regeants used: I2 / OH- Functional Groups tested: Methyl ketones Positive results: Yellow precipitate forms (CHI3) Silver Nitrate - correct answer Reagents used: AgNO3 in alcohol Tests for: Alkyl halides Positive results: Precipitate of Ag compound formed Bromine Test - correct answer Reagents used: Br2/CCl4 Functional Groups tested: Alkenes and alkynes Positive results: Brown color of Bromine disappears Baeyer Test - correct answer Reagent: Dilute KMnO4 Functional groups tested: Alkenes and alkynes Positive results: Purple solution turns to brown precipitate Jones Test - correct answer Regeants used: CrO3 / H2SO4 Functional groups tested for: 1° and 2° alcohols Positive results: Orange reagent turns blue-green -Used in breathilizers to test for drunk drivers Lucas Test - correct answer Reagents used: ZnCl2 / HCl Functional groups tested for: 2°, 3°, and benzylic alcohols Positive test results: Cloudy solution initially, then separate layer forms