chlorination - Radical Chlorination of 1-Chlorobutane. The...

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Radical Chlorination of 1-Chlorobutane. The purpose of this experiment is to examine a possible polar effect on a free radical chlorination. When butane is chlorinated at 75° in the liquid phase, one observes 63% attack at the secondary hydrogens and 37% attack at the primary hydrogens. Because there are six CH 3 hydrogens and four CH 2 hydrogens in butane, to compare the reactivity at each position, we must convert these results to % attack per hydrogen. CH 2 attack: 63%/4 CH 2 hydrogens = 15.8%/CH 2 hydrogen CH 3 attack: 37%/ 6 CH 3 hydrogens = 6.2%/ CH 3 hydrogen This results in a relative reactivity (RR) for CH 2 to CH 3 hydrogens of RR(CH 2 / CH 3 ) = 15.8/ 6.2 = 2.5 This means that under these reaction conditions, a CH 2 hydrogen is 2.5 times more reactive than a CH 3 hydrogen. In the chlorination of 1-chlorobutane by sulfuryl chloride (assume that the attacking radical is Cl• ), you will measure the % attack at each of the four non-equivalent positions by an analysis of the gas chromatogram of the product mixture. The results will be discussed in terms of a possible polar effect on the reaction. Hint: the chlorine atom is a powerful electrophile ( electron seeker). Reaction rate will be faster at positions having what characteristic? Experimental . Turn on the sand bath immediately and begin heating a 30 mL beaker, half filled with water, to about 80°. As this is heating, you can measure out the reagents and set up the apparatus. The experimental procedure is quite simple, but care must be taken in working with the hazardous sulfuryl chloride. The 1-chlorobutane is used in large excess and the azo compound is used in a catalytic amount so quantities do not have to be measured with great accuracy. The data that we wish to obtain is the product distribution (ratio of isomeric dichlorides) - small differences in amounts of reagents will have no effect on the ratios. The apparatus must be free of water. CAUTION : sulfuryl chloride is caustic and noxious and can react vigorously with
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chlorination - Radical Chlorination of 1-Chlorobutane. The...

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