07. T.A. Michael Hall
The purpose of this experiment is to determine the reactivity of hydrogen atoms on a carbon chain using free radical chlorination. In this experiment 1-chlorobutane will be chlorinated with the combination of sulfuryl chloride and ABCN as an initiator to produce the chlorine radicals. The combination of 1-chlorobutane and sulfur chloride will produce four dichlorobutane isomers. The isomers produced and their reactivity will be analyzed by the amounts of isomers produced in the product and by gas chromatography.
1) Assemble the apparatus in the hood using a Thermowell Heater 2) Use a 25-mL round bottom flask fitted with a reflux condenser which will be connected through a vacuum adapter to a 500-mL filter flask. a. close vacuum adapter w/ cork and make sure the inlet tube does not reach the surface of the water in the filter flask b. make sure any water from the trap does not get sucked back into the reaction flask c. glass tube must not dip below the surface of the water in the trap 3) Note the differences on pg.77 of G&M fig. 2.65(b)
a. it does not use a water aspirator or house vacuum b. Fit #7 one-hole rubber stoppers w/ a length of glass tubing about 15cm long. c. Tubing needs to be fire-polished on both ends and lubricate hole in stopper with glycerin. d. Use cloth towel to protect your hands as you insert the tubing into the stopper and wipe off excess glycerin. 4) Add stirbar, .1g of 2,2-azobis(cyclohexanenitrile), 5mL of 1-chlorobutane and 2-mL of sulfuryl chloride and place in flask 5) Stopper and weigh. Then hook flask to reflux condenser 6) Heat solution for 20 minutes, let cool below reflux temperature and check weight. If the weight loss is not enough continue to next step 7) Add a second .1g of 2,2-azobis(cyclohexanenitrile) and heat for another 10 minutes. 8) Weigh flask. If proper amount of weight in not lost after both heating periods, just continue with experiment. 9) Cool reaction mixture in ice-bath, then add 15-mL of ice cold saturated to aqueous sodium chloride (brine) 10) Transfer the resulting two-phase solution to a separatory funnel and separate layers. 11) Wash the organic layer with 10-mL of .5 M sodium carbonate solution (don’t forget to vent) 12) Use pH paper to determine whether the aqueous layer is basic a. If it is not basic, wash organic layer with another 10-mL of sodium carbonate solution until it becomes basic. 13) After washing the organic layer with brine transfer to Erlenmeyer flask and add several scoops of anhydrous sodium sulfate 14) Swirl for 10-15 minutes during drying period ( the liquid should start to become clear, if not add more drying agent) 15) Decant organic layer into a dry, tarred container
16) Calculate the following:
a. Theoretical yield of product
b. Amount of unreacted 1-chlorobutane
c. theoretical weight of material (product plus unreacted starting material) expected d. percentage yield of material recovered
17) Analyze the organic mixture directly by gas chromatography 18) From chromatography data, determine percentage composition of the mixture of the four isomeric dichlorobutanes produced in the reaction
Main Reaction and Mechanism:
Table of Reagents:
|Compound |Amounts Used |Molecular Weight |Boiling Point|Melting Point |Density | | | |(amu) |(0C) |(0C) |(g/mL) | |1-chlorobutane |5.0-mL |92.57...