CH3CH2CH = CH2 + H2O H+ 
__major product + __ minor product
The Correct Answer and Explanation is :
The reaction described, CH3CH2CH=CH2 (1-butene) reacting with H2O in the presence of an acid catalyst (H+), is a typical example of an acid-catalyzed hydration reaction. In this reaction, water is added across the double bond of the alkene, leading to the formation of an alcohol.
Major Product: The major product of this reaction is 2-butanol. The mechanism involves the protonation of the double bond to form the most stable carbocation intermediate. For 1-butene, protonation of the double bond forms a secondary carbocation at the second carbon (more stable than a primary carbocation that would form if the double bond at the first carbon was protonated). Water, acting as a nucleophile, then attacks this carbocation, leading to the formation of 2-butanol after deprotonation.
Minor Product: The minor product of this reaction is 1-butanol. Although less favorable, the formation of 1-butanol involves the same initial step of protonation of the double bond to form a carbocation. However, in this less common pathway, the carbocation rearrangement might occur, shifting the positive charge from the second carbon to the first carbon (hydride shift), or water might attack the less stable primary carbocation formed directly at the first carbon. The result is the formation of 1-butanol after deprotonation.
Explanation:
The preference for the formation of 2-butanol over 1-butanol is based on the stability of the carbocation intermediate formed during the reaction. Secondary carbocations are more stable than primary carbocations due to greater spreading of the positive charge over the neighboring carbon atoms. In the hydration of 1-butene, the secondary carbocation formed at the second carbon is more stable and thus more likely to form, making 2-butanol the major product.
The reaction’s selectivity can be influenced by the conditions under which it is performed, such as the concentration and strength of the acid used, which affects the rate of carbocation formation and stability. The water concentration can also play a role in determining the rate at which it can attack the carbocation and close the reaction pathway.
Hydration reactions are significant in organic synthesis because they provide a direct route to alcohols from alkenes, which are commonly available. Moreover, understanding the reaction mechanism and factors influencing product distribution is crucial for designing efficient synthetic routes in industrial and laboratory settings.
Now, let’s generate an image to visualize these molecules and their reaction.
Here is a detailed illustration of the acid-catalyzed hydration reaction of 1-butene to form 2-butanol and 1-butanol. The image includes all the steps of the reaction mechanism, such as protonation, carbocation formation, nucleophilic attack by water, and deprotonation, showing how 2-butanol is formed as the major product and 1-butanol as the minor product. Each molecular structure is clearly labeled to aid in understanding the process. You can click on the image to view it in greater detail.
