Question

how does the mixture of isomeric alkenes produced by an acid-catalyzed dehydration reaction compare with the alkene mixture from a base-catalyzed dehydrochlorination reaction? Are either or both sets or products influenced primarily by product stability?

E1/E2 Elimination Reactions. Acid-Catalyzed Dehydration of 2-Me Base-Catalyzed Dehydrochlorination of 2-Chloro-2-methylbutane Acid-Catalyzed Dehydration of 2-Methyl-2-butanol and Adapted for an experiment published in More J.R - Hammond, C.N. Schatz, PF: Morrill, T.C.: Modern Projects and P. Hammond CN: Schatz, P.F., Morrill... Experiments in Organic Chemistry, 2nd ed., Freeman: New York, 2003. Question: How does the miya does the mixture of isomeric alkenes produced by an acid catalyzed dehydration reaction compare with the alkene or from a base-catalyzed dehydrochlorination reaction? Are either or both sets of products influenced primary by product stability? Experiment Overview: This is a two-period project. In Part A, you will carry out the dehydration of 2-methyl-2-butanol with H2SO4 and determin the product composition by gas chromatography, Then the following period in Part B, you will dehydrochlorinate 2-chloro-2- methylbutane by treatment with KOH and together compare the ratio of alkenes produced in the base-catalyzed dehydrochlorination to the ratio of alkenes produced by the acid-catalyzed dehydration of 2-methyl-2-butanol H₃C CH₂ Heat CH3 Part A: Acid-Catalyzed Dehydration of 2-Methyl-2-butanol OH CH₂ HASO4 CH3-CH2-C-CH CH3-CH2-C CHE CH3 2-Methyl-2-butanol 2-Methyl-1-butene (tert-amyl alcohol) bp 31.1°C bp 102 C MW 70.1 MW 88.1 density 0.650 g/ml density 0.813 g/ml 2.Methyl-2-butene bp 38.5°C MW 70.1 density 0.662 g/mL. 1 " --sid the mainr nroduct is a mixture of alkenes.

Answer 1

Acid catalysed dehydration of alcohol (major product) more stable alkene (minor product) Less stable alkene According to the Zaitsev's rule, the most substituted product will be the most stable, and therefore the most favored. rule is being followed by both the acid catalysed as will as base catalysed elimination reactions. Base catalysed dehydrochlorination of alkyl chloride (major product) More substituted, therefore more stable alkene (minor product) less substituted, therefore less stable alkene In both acid as wellas base catalysed rections, formation of major product is influenced by product stability