Sulfuryl chloride 1-chlorobutane

In the first experiment we will chlorinate 1-chlorobutane because it is easier to handle in the laboratory than gaseous butane and we will use sulfuryl chloride as our source of chlorine radicals because it is easier to handle than gaseous chlorine. Instead of using light to initiate the reaction we will use a chemical initiator, 2,2 -azobis-(2-methylpropionitrile). This azo compound (R—N=N—R) decomposes at moderate temperatures (80-100°C) to give two relatively stable radicals and nitrogen gas ... 

To a lOO-mL round-bottomed flask add 1-chlorobutane (25 mL,21.6 g,0.23 mole), sulfuryl chloride (8 mL, 13.5 g, 0.10 mole), 2,2 -azobis-(2-meth-ylpropionitrile) (0.1 g) and a boiling chip. Equip the flask with a condenser and gas trap as seen in Fig. 1. Heat the mixture to gentle reflux on the steam bath for 20 min. Remove the flask from the steam bath, allow it to cool somewhat and quickly, to minimize the escape of sulfur dioxide and hydrochloric acid, lift the condenser from the flask and add a second 0.1-g portion of the initiator. Heat the reaction mixture for an additional 10 min, remove the flask and condenser from the steam bath, and cool the flask in a beaker of water. Pour the contents of the flask through a funnel into about 50 mL of water in a small separatory funnel, shake the mixture, and separate the two phases. Wash the organic phase with two 20-mL portions of 5% sodium bicarbonate solution, once with a 20-mL portion of water, and then dry the organic layer over anhydrous calcium chloride (about 4 g) in a dry Erlenmeyer flask. The mixture can be analyzed by gas chromatography at this point or the unreacted 1-chlorobutane can be removed by fractional distillation (up to bp 85°C) and the pot residue analyzed by gas chromatography. 

Assembly Assemble the apparatus for heating under reflux, and attach a gas trap, such as that of Figure 2.69, to the top of the condenser. Place a spinvane in the vial and add 10 mg (0.010 g) of 1,1 -azobis(cyclohexanecarbonitrile) (ABCN). Working at the hood, sequentially add 0.5 mL of 1-chlorobutane and 0.2 ml (200 piL) of sulfuryl chloride to the vial. Cap and weigh the vial, and then attach it to the reflux condenser, working quickly to minimize introducing vapors of sulfuryl chloride into the atmosphere. 

Using curved arrows to symbolize the flow of electrons, write the complete mechanism for the formation of 1,3-dichlorobutane from 1-chlorobutane using ABCN (1) and sulfuryl chloride. Clearly label each step as to whether it is part of the initiation, propagation, or termination steps. 

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