Homework SourseA Why does dehydration proceed under acidic conditions BWoul
A. Why does dehydration proceed under acidic conditions? B.Would you expect the same reaction to occur under basic conditions? Explain.
Solution
Dehydration means removal of water molecule.When heated with strong acids catalysts (most commonly H2SO4) alcohols typically undergo a 1,2-elimination reactions to generate an alkene and water.Also known as dehydration since it involves the removal of a molecule of water.
Since Alcohols are amphoteric.they can act both as acid or base. The lone pair of electrons on oxygen atom makes the –OH group weakly basic.Oxygen can donate two electrons to an electron-deficient proton.
An acid/base reaction.Protonation of the alcoholic oxygen to make a better leaving group. This step is very fast and reversible.The lone pairs on the oxygen make it a Lewis base.Cleavage of the C-O bond allows the loss of the good leaving group, a neutral water molecule,
| Dehydration proceeds under acidic conditions because the alcohol group can be protonated creating an very good leaving group in a water molecule. Under basic conditions,OH- is a very poor leaving group and E2 Elimination will not take place. |
