Question

Dehydration Experiment: 1. Show all appropriate electron-pushing arrows to explain the formation of each of the observed products in the following reaction. Because intermediates have been provided for you, all arrows must be perfect and must be clear to get credit. 9M H,SO 20- s-d-o g- 2. "Rearrangements" like you see above are fairly common in Snl (and El) reactions, but are never seen in Sy2 or E2 reactions. Why don't those latter mechanisms ever allow rearrangement to occur?

Answer 1

H-HSO4 OH M H,SO HSO4 H H Alcohol is protonated and leaves as water. Then ring contraction occurs followed by 1,2 hydride shift occurs to give tertiary carbocation. Finally elimination occured to give the oelfine. 2 "Rearrangements" like you see above are fairly common in Sy1 (and El1) reactions, but are never seen in Sx2 or E2 reactions. Why don't those latter mechanisms ever allow rearrangement to occur? SN, and E, reactions are two step reaction. Generally they proceed via carbocations SN2 and E2 reactions are concerted (One step) reaction. They dont proceed via any stable intermediate like carbocation and other species. They directly converted to product. Hence they never seen such rearrangements