Experiment 10:. ACID-CATALYZED DEHYDRATION OF AN ALCOHOL WITH REARRANGEMENT. Objectives. To synthesize isomeric alkenes from a 2 o alcohol. To determine major product using GC analysis. To understand product distribution using molecular modeling.
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OF AN ALCOHOL
Threedifferent ISOMERIC alkenes can be produced. Because this reaction is performed near equilibrium conditions, the relative amount of each product reflects its stability.
The rate of elimination of water depends on the stabilityofthe carbocation formed. Formation of the carbocation is the most energetically unfavorable, and therefore the slowest, step in dehydration reactions.
2. …which forms a new O-H bond, where oxygen bears a positive charge (oxonium ion). Water is eliminated-forms 2o carbocation.
1. The hydroxyl oxygen attacks and removes a proton from sulfuric acid…
3. Products may form from the 2o carbocation, but it is more likely that the 2o C+ will rearrange to a 3o C+.
4. At the carbocation stage, water will remove a proton from the carbon ADJACENT to the carbocation. The electrons form the pi bond of the alkene.
# g starting material 1 mol of starting material 1 mol product # g # g 1 mol starting material 1 mol product
Amount you started with
Molecular weight of starting material
Molecular weight of product
% transmittance of IR radiation
Frequency of vibration (in wavenumbers)
Full IR Absorption Correlation Table in Appendix J
IR spectra are on page 87 in lab manual!