Isopropyl alcohol is obtained by reacting which of the following alkenes with concentrated \(\mathrm{H}_{2} \mathrm{SO}_{4}\) followed by boiling with water? (a) 2-methylpropene (b) Ethylene (c) Isoprene (d) Propylene

An electrophilic addition reaction is an essential process in organic chemistry, where an electrophile and a nuleophile combine to form more complex molecules. Imagine you're building a puzzle; the pieces need to fit together perfectly. Similarly, in chemistry, the positively charged electrophile seeks a negatively charged part of another molecule to form a stable, connected structure.

In the context of synthesizing isopropyl alcohol, the alkene serves as the puzzle piece with an area that attracts the electrophile due to its double bond. This double bond is high in electron density, making it an ideal target for the electrophile, which in this case is concentrated sulfuric acid (H_{2}SO_{4}). During the reaction, the acid donates a hydrogen (H) to the alkene, creating a carbocation intermediate. This intermediate is pivotal because it's like an incomplete puzzle, ready to accept another piece to complete the picture.

In summary, electrophilic addition is like finding and connecting the right puzzle pieces in the molecular world. It's characterized by the transfer of electrons from a substance rich in electrons (alkene) to an electron-lover (electrophile), culminating in a new and more complex molecule.

Sulfuric acid, often symbolized as H_{2}SO_{4}, isn't only known for its corrosive properties or involvement in battery acid; it plays a transformative role in the organic synthesis of alcohols from alkenes. Think of H_{2}SO_{4} as a skilled matchmaker, ready to introduce alkenes to a new bond that will change their lives forever. It doesn't just hand over one of its hydrogen atoms to the double bond; it sets up a structure that eagerly awaits the next phase of the reaction.

When H_{2}SO_{4} meets an alkene, it triggers the electrophilic addition reaction we talked about. But it's more than just a fleeting encounter—the reaction forms an alkyl hydrogen sulfate intermediate, a crucial step in leading towards the desired alcohol. In this intermediate stage, the molecule is prepped and almost ready to welcome water (H_{2}O) into the mix. This preparation phase, orchestrated by sulfuric acid, is vital to ensure a smooth transition to the final alcohol product. It's akin to setting the stage for the grand finale in a play where every actor knows their cue.

Markovnikov's rule might sound like something from a historical text, but it's a straightforward concept guiding chemists through the maze of organic synthesis. When you're deciding where to add a new decorative piece to your outfit, you'd likely put it where it makes the most impact. In the synthesis of alcohols from alkenes, Markovnikov's rule helps you decide where to attach the new component—the hydroxyl group (OH).

The rule states that in an addition reaction of hydrogen halides to alkenes, the hydrogen atom is added to the carbon with the greater number of hydrogen atoms, and the halide (or in our case, the OH group from water) bonds with the carbon with fewer hydrogen atoms. This happens because the stability of the resulting carbocation intermediate is greatest when more alkyl groups are surrounding it.

In our search for the correct precursor to isopropyl alcohol, we seek an alkene that obeys Markovnikov's rule and results in the formation of a secondary alcohol. Propylene fits the bill perfectly here, as it can yield a secondary carbocation that will attract the OH from water to produce isopropyl alcohol, following this rule like a seasoned actor hitting their mark on stage.