Textbook Question
Predict the product(s) that would result when the alkenes shown here are allowed to react under the following conditions: (iv) H2SO4 , H2O
(k)
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10. Addition Reactions
Acid-Catalyzed Hydration
6:09 minutesProblem 29b
Textbook Question
How can the following compounds be prepared from 3,3-dimethyl-1-butene?
b. 3,3-dimethyl-2-butanol
Verified step by step guidance1
Step 1: Recognize that 3,3-dimethyl-1-butene is an alkene, and the target compound, 3,3-dimethyl-2-butanol, is an alcohol. This suggests that the reaction will involve the addition of a hydroxyl group (-OH) to the alkene.
Step 2: To achieve the desired product, consider the regioselectivity of the reaction. Since the hydroxyl group needs to be added to the second carbon (to form 3,3-dimethyl-2-butanol), the reaction must follow Markovnikov's rule. This rule states that the -OH group will add to the more substituted carbon of the double bond.
Step 3: Use an acid-catalyzed hydration reaction to achieve the Markovnikov addition of water (H₂O) across the double bond. The reaction typically involves using a dilute acid, such as H₂SO₄, in the presence of water. The mechanism involves protonation of the double bond to form a carbocation intermediate, followed by nucleophilic attack by water and deprotonation to yield the alcohol.
Step 4: Consider the possibility of carbocation rearrangement. In this case, the carbocation formed after protonation of the double bond is already tertiary (on the second carbon), which is stable. Therefore, no rearrangement occurs, and the hydroxyl group will attach to the second carbon.
Step 5: After the reaction is complete, isolate and purify the product, 3,3-dimethyl-2-butanol, using standard organic chemistry techniques such as distillation or recrystallization, depending on the physical properties of the product.
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Video duration:
6mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Alkene Reactivity
Alkenes, such as 3,3-dimethyl-1-butene, are reactive due to the presence of a carbon-carbon double bond. This double bond can undergo various reactions, including hydration, hydrohalogenation, and oxidation, allowing for the transformation of alkenes into alcohols and other functional groups. Understanding the reactivity of alkenes is crucial for predicting the products of reactions involving them.
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Markovnikov's Rule
Markovnikov's Rule states that in the addition of HX (where X is a halogen) to an alkene, the hydrogen atom will attach to the carbon with the greater number of hydrogen atoms already attached. This principle helps predict the regioselectivity of reactions, such as the formation of 3,3-dimethyl-2-butanol from 3,3-dimethyl-1-butene, where the alcohol group will preferentially attach to the more substituted carbon.
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Hydration of Alkenes
The hydration of alkenes involves the addition of water (H2O) across the double bond, typically in the presence of an acid catalyst. This reaction converts alkenes into alcohols, such as 3,3-dimethyl-2-butanol from 3,3-dimethyl-1-butene. Understanding the mechanism of hydration, including carbocation formation and rearrangement, is essential for predicting the outcome of such transformations.
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