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Chapter

CHEM 235 Chapter Notes -Glycerol, Stopcock, Boiling Chip


Department
Chemistry
Course Code
CHEM 235
Professor
Dana Zendrowski

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Experiment 7 Procedure
1) Put 15 mL amyl alcohol & 20 mL acetic acid into 100 mL RB flask
2) Add 3 mL sulfuric acid, little at a time while swirling
3) Add boiling chip and set up system for reflux (20 minutes)
a. See pg A-63 observe where clamp is placed in setup
4) During reflux:
a. Pre-weigh 3 large test tubes w/ cork (in beaker; tare beaker first)
b. Cool test tubes in large beaker ice bath
c. Get/clean large separatory funnel
d. Collect all wash solvents for extraction
5) Remove heat source and let mixture cool for few minutes then ice bath
6) Once cooled, transfer to separatory funnel
a. Note:
i. Make sure stopcock is closed
ii. Place a beaker underneath
iii. Before extracting, remember to remove stopper
iv. At end of extractions, collect top layer into separate flask and cork!
7) Wash organic layer with 2 X 25 mL H2O
8) Wash organic layer with 2 x 15 mL 5% NaHCO3 (release pressure more often)
9) Check aqueous layer to see if its basic in last wash
a. If acidic: wash once more with NaHCO3
10) Wash organic layer with 15 mL saturated NaCl
11) Pour ester into dry 50 mL E. flask and dry w/ MgSo4 for 10 minutes
a. Add until free grains seen, tighten cork and swirl
12) Calibrate thermometer
a. Prepare ice bath in 400 mL beaker, place thermometer and wait
b. Place small drop of glycerol at tip and insert into still head adaptor until immersion line
covered
13) Filter ester into 50 mL RB flask with fluted filter paper
14) Add boiling chip to RB flask and setup simple distillation
a. Clamp RB flask to vertical bar w/ 2-prong clamp; attach still head adaptor on top of flask
i. Wrap with aluminum foil
b. Secure take off adaptor to condenser w/ elastic band & attach tubings to condenser
c. Join condenser to still head adaptor & clamp condenser to H. bar w/ 3-prong clamp &
put rubber tubings over bar; connect lower tube to water tap
d. Connect heating mantle to rheostat & position mantle snuggly under RB flask w/ ring
clamp and wood board; plug in rheostat;
e. Turn to high heat until boiling, then reduce until 1 drop/second
15) During distillation, discard cloudy product, and collect fraction boiling b/w 139-149
a. DON’T DISTILL TO DRYNESS; remove thermowell & turn spout of takeoff adaptor UP
16) Weigh desired fraction & calculate percentage yield
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