Electrophilic Addition

Topics: Alkene, Bromine, Sodium bicarbonate Pages: 3 (764 words) Published: September 27, 2007

The purpose of this lab is to learn how to synthesize 2-methyl-2-butene into 2-bromo-2-methylbutane using addition of hydrogen bromide.


Chemical CompoundMolecular FormulaMolecular WeightBoiling PointMelting PointDensity AmyleneCH3CH=C(CH3)270.13 g/mol36 oC-134 oC0.662 g/ml
Hydrobromic AcidHBr80.91 g/mol126 oC-11 oC1.490 g/ml
2-Bromo-2-MethylButaneC5H11Br151.05 g/mol107 oC1.18 g/ml Sodium bicarbonateNaHCO384.007 g/molDecomposes at melting pointunknown2.159 g/ml Diethyl etherC2H5OC2H574.12 g/mol34.6 °C−116.3 °C0.7134 g/ml

In this lab we use electrophilic addition of a hydrogen halide to an alkene to make 2-bromo-2-methylbutane. Electrophilic addition is an addition reaction where a pi bond is removed to create two new covalent bonds, Y-Z + C=C → Y-C-C-Z. Electrophilic addictions can also be the reverse of dehydrohalogenation. Dehydrohalogenation is when a double bond is formed between the α- and β-carbon. In this lab the addition of hydrogen bromide produces a more substituted alkyl halide with respect to Markovnikov's rule where the Bromine atom attaches to the more substituted carbon.**

**According to lab manual, www.wikipedia.com

First we mixed 25ml of hydrobromic acid and 10mlof amylene in a 50ml flask. Then we attach the apparatus and reflux the solution for 30 minutes by heating the solution until it boils, after this we allow the solution to cool down and then poured it into a125ml separatory funnel to drain and discard the lower spent acid layer. We washed the organic layer with a combination of 20ml of saturated sodium bicarbonate solution and 20ml of ether. Then we drained the lower aqueous layer and we kept the organic layer. We added 4 to 5 pellets of calcium chloride to the organic layer and allowed the solution to dry for 10 minutes. After this we placed the dry ether solution in a 50ml flask and fractionally...
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