# What would be the mechanism of the given reaction?

Problem:

$\ce{A}$ can be?

1. concentrated sulphuric acid
2. alcoholic potassium hydroxide
3. triethylamine
4. potassium tert-butoxide

Option (A): Conc. $\ce{H2SO4}$, is an acid, it gives $\ce{H+}$ ions which must act like electrophile and add to the double bond, which must produce a carbocation and then, $\ce{HSO4^-}$ ion must act like a nucleophile and form a bond with the carbocation. Hence, the reaction must be addition of $\ce{H+}$ and $\ce{HSO4^-}$

Options (B),(C),(D): are bases, with basicity order: (D) > (B) > (C). But what would they do to an alkene?

Answer given in the book is A. How is this so?

• Under (A) you have heat added. What is to stop a second molecule reacting with the first under electrophilic addition to remove the H2SO4 as a good leaving group and give the product shown in the question? – Nick Jan 14 '13 at 15:36

Bottom line: $\ce{HSO4-}$ is a really bad nucleophile, and it doesn't enter in the picture.