Question

The product formed by acid catalysed hydration of 2-phenyl propene is: (a) 3-phenyl-2-propanol (b) 1-phenyl-2-propanol (c) 2-phenyl-2-propanol (d) 2 -phenyl-1-propanol

Short answer

The product is 2-phenyl-2-propanol (option c).

Step-by-step solution

Understand the Reaction

The reaction of interest is the acid catalyzed hydration of an alkene, specifically 2-phenyl propene. This means that water, in the presence of an acid, adds across the double bond of the alkene.

Determine the Major Product

In acid-catalyzed hydration, Markovnikov's rule is applied, where the hydrogen atom from water adds to the less substituted carbon atom of the double bond, and the hydroxyl group (OH) adds to the more substituted carbon atom. For 2-phenyl propene, the double bond is between the second and third carbon atoms adjacent to the phenyl group.

Apply Markovnikov's Rule

According to Markovnikov's Rule, the OH group will attach to the more substituted carbon atom, which in 2-phenyl propene is the second carbon atom where the alkene's double bond is located, given it is bonded to the phenyl group (making it more substituted). The hydrogen atom from the water will attach to the less substituted third carbon atom.

Identify the Product

With the OH attaching to the second carbon (the more substituted one), the resulting product will be 2-phenyl-2-propanol, as the OH group is bonded to the same carbon atom that also bears the phenyl group.

Key concepts

Markovnikov's Rule

In organic chemistry, understanding how molecules react can be made easier with certain rules. One key rule is Markovnikov's Rule. Named after Russian chemist Vladimir Markovnikov, this rule helps predict the outcome of addition reactions involving alkenes. When a molecule splits into two parts and adds across a carbon-carbon double bond, Markovnikov's Rule tells us how these parts will attach.
For example, when dealing with alkenes, which are hydrocarbons with one or more double bonds, hydrogen will attach to the carbon with more hydrogen atoms. This is the less substituted carbon. Meanwhile, other groups, like the hydroxyl group (OH) in acid-catalyzed hydration, will attach to the more substituted carbon with fewer hydrogen atoms.
This guiding principle is essential for predicting the structure of the final product when dealing with certain reactions, such as the acid-catalyzed hydration of alkenes.

Acid-catalyzed hydration

Acid-catalyzed hydration is a significant reaction process in organic chemistry, particularly for converting alkenes into alcohols. This reaction requires three crucial components: an alkene, water, and an acid. The acid, often a strong one like sulfuric acid, acts as a catalyst and facilitates the reaction without being consumed.
The process starts as the alkene's double bond is protonated by the acid, resulting in the formation of a carbocation. This positively charged intermediate then attracts the negatively charged part of the water molecule, which is the hydroxyl group (OH). Following Markovnikov's Rule, the OH group attaches to the more substituted carbon, while a hydrogen atom attaches to the less substituted carbon. Hence, the double bond's electrons facilitate this entire transfer.
Acid-catalyzed hydration is a pivotal method for synthesizing alcohols from alkenes. Its understanding is crucial for students aiming to master organic reaction mechanisms.

Alkenes

Alkenes are organic compounds composed of carbon and hydrogen, with at least one carbon-carbon double bond in their molecular structure. These unsaturated hydrocarbons are part of a larger family of compounds known for their reactivity due to the presence of this double bond.
The double bond in alkenes provides an opportunity for chemical reactions to occur, like addition reactions, where new atoms can be added to the original compound. This reactivity is due to the shared pair of electrons in the double bond, which makes alkenes more reactive than their alkane counterparts.
In the case of acid-catalyzed hydration, alkenes serve as the starting material, reacting in such a way that follows Markovnikov's Rule. Understanding the basic properties and reactivity of alkenes is fundamental in predicting the outcomes of various organic reactions, particularly those involving the addition of functional groups like OH to form alcohols.