Chem 35 Lecture 4 Functional Group Tests (cont.) and Sample Problem Structure Property Relationships Distillation Lab Tips and Comments Quick Quiz 4 on HDI, Functional Group Tests
Quiz 1 (~1/2 hr) next Tues: • Molecular formulas from % composition & M.W. • Hydrogen Deficiency Index & possible structures. • Functional Group Tests - Know Func. Group Tests demonstrated: Br2, H2, KMnO4, Na, CrO3, DNP, burning, acid and base solubility. • Assigned problems on above through LG-11.29 • Lab Equipment - Lab Guide Intro. pp i - xiii • Safety - Lab Guide Ch 2 • Recrystallization Ch 4
Quick Quiz 3: Calculate the Hydrogen Deficiency Index for C5H10O and draw any two possible structures fitting this formula, one of which is a ketone.
Aromatic Compound Functional Group Tests sooty smoky orange flame when burned versus Br2, KMnO4 or CrO3 alkanes and oxygentated compounds such as alcohols Hot KMnO4 No Reaction clear, blue-yellow flame (like gas stove)
Six concepts that help to predict physical properties - M.P., B.P., Solubility, Chromatographic Behavior 1. Molecular Weight (London Forces). CH4 versus CH3CH2CH2CH2CH2CH3 versus CH3CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH3 n-C20H42
2. Hydrogen bonding. • CH3CH3 vs. CH3OH bp = -116 vs +68°C
Acetic acid: 4. Non-polar hydrocarbon backbone Vs. polar & H-bonding functional groups. versus Stearic acid: "Like Dissolves Like"
5. The basicity of nitrogen e- lone pairs. 1°, 2°, or 3° amine
6. Resonance (in oxy anions) -> Acids. Benzoic acid Phenol
Compound A has the formula C3H8O and produces H2 gas when treated with metallic sodium. An orange solution of CrO3 reacts with compound A, turning blue green and giving compound B, C3H6O2. Compound B reacts with NaHCO3 to produce CO2 gas, and does NOT form bright yellow crystals of a dinitrophenylhydrazone. Give possible structures for both A & B. Sample HDI/FGT Problem
The Evolution of Distillation Ancient Alembic Modern Refinery
Distillation Set-Ups Simple Distillation- Fig 5.2 Glass + rubber thermometer adapter Ring stands 3-way connecting piece West Condenser Rubber band to hold conn. tube on 100-mL flask with 1” stir bar Connecting tube Water in 10-mL grad. cylinder distillate receiver Varistat Heating Mantle Water out
Distillation Set-Ups Glass wool Fractionating column half full of metal helices • Fractional Distillation- Fig 5.3 Water in Pipet bulb Steel wool
Distillation Graphs - 1. Temperature versus Volume bp of pure B Simple distillation Temperature °C Fractional distillation bp of pure A Volume (or time)
Distillation Graphs - 2. Temperature versus Liquid and Vapor Composition 0 40 20 100 60 80 % Cyclohexane
Distillation: • Next week, you will be doing Procedure 1A or 1B or 2A or 2B. Only need to write up PreLab for one of these. • Everyone writes PreLab for Procedure 3. This will be carried out the following week • Complete and turn in photocopy of Common Shelf Chemical Data Table with PreLab…also regular Chemical Data Table for 2 other organic liquids not on Common Shelf (n-butanol and t-butanol).
Other Lab Comments • You will receive your spectral unknown (don’t mix up with Recryst. Unknown) • Take mp’s of crude and recrystallized mp unknown and spectral unknown during next two labs