Question

complete #1 and #2 and please explain!

Nucleophilic Substitutions: Competing Nucleophiles Dry Lab Name When an alcohol (substrate) is placed in an excess equimolar amounts of chloride ions and bromide ions in acid media the corresponding alkyl halides are obtained. The ratio of the alkyl halides depends on several factors: the nature of the substrate, the reaction conditions, the solvent and the mechanism of the reaction. (Refer to your lab textbook, see syllabus schedule) When fert-butanol (density 20 °C-0.7858 g/mL) is placed in the presence of excess equimolar amounts of chloride and bromide ions in aqueous acid experimental data indicates 45% tert-butyl chloride and 55% tert-butyl bromide is obtained. This outcome can be explained by the fact that the rate determining step of the reaction does not involve the nucleophile, and once the carbocation is formed it is equally available to each nucleophile. On the other hand, when -butanol (density 20 °C =0.810 g/mL) is placed in the presence of excess equimolar amounts of chloride and bromide ions in aqueous acid experimental data indicates 16% of n-butyl chloride and 84% of n-butyl bromide is obtained. The difference in the outcome can be explained by the fact that the rate determining step of this reaction requires the presence of the nucleophile, and in aqueous media the small size chloride ion gets "trapped" in the aqueous solvent cage and the bromide ion therefore gets a better chance to attack the substrate. This point can be demonstrated by changing the solvent. When n-butanol is placed in the presence of excess equimolar amounts of chloride ions and bromide ions in acid dimethyl sulfoxide the experimental data provides an 84% n-butyl chloride and 16% n-butyl bromide as the outcome. Start of Exercise: 1. Write balanced chemical equations for all three reactions (hint: account for the mole ratios!). 2. Draw complete mechanisms for all three reactions.