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Ch. 8 - Alkenes I: Properties and Electrophilic Additions
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
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All textbooksMullins 1st EditionCh. 8 - Alkenes I: Properties and Electrophilic AdditionsProblem 31e
Chapter 7, Problem 31e

What is the expected product for the reaction of each of the following alkenes with (i) HBr and (ii) HCl?
(e)

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1
Identify the alkene structure in the image. The structure shown is a cyclohexene ring with an alkene group, which is a six-membered ring with a double bond.
Understand the reaction mechanism: The addition of HBr or HCl to an alkene follows Markovnikov's rule, where the hydrogen atom from the acid will add to the less substituted carbon atom of the double bond, and the halide (Br or Cl) will add to the more substituted carbon atom.
Apply Markovnikov's rule: In the cyclohexene ring, the double bond is between two carbon atoms. Determine which carbon is more substituted. The more substituted carbon is the one with more carbon atoms attached to it.
Predict the product for the reaction with HBr: The hydrogen from HBr will add to the less substituted carbon, and the bromine will add to the more substituted carbon, resulting in a bromocyclohexane.
Predict the product for the reaction with HCl: Similarly, the hydrogen from HCl will add to the less substituted carbon, and the chlorine will add to the more substituted carbon, resulting in a chlorocyclohexane.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Electrophilic Addition

Electrophilic addition is a fundamental reaction mechanism in organic chemistry where an electrophile reacts with a nucleophile, typically involving alkenes. In this process, the double bond of the alkene acts as a nucleophile, attacking the electrophile (like HBr or HCl), leading to the formation of a more stable carbocation intermediate. This mechanism is crucial for predicting the products of reactions involving alkenes.
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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 rule helps predict the regioselectivity of the reaction, guiding chemists in determining the major product formed when alkenes react with hydrogen halides like HBr and HCl.
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Carbocation Stability

Carbocation stability is a key concept in organic chemistry that refers to the relative stability of positively charged carbon species. Carbocations are classified as primary, secondary, or tertiary based on the number of alkyl groups attached to the positively charged carbon. Tertiary carbocations are the most stable due to hyperconjugation and inductive effects, influencing the pathway and products of electrophilic addition reactions.
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Related Practice
Textbook Question

Would you expect but-2-ene or 2-methylbut-2-ene to react more quickly with HBr?

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Textbook Question

In your own words, explain why it is not possible to make primary alkyl halides, such as 1-bromopentane, using the electrophilic addition of HCl or HBr to an alkene.

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Textbook Question

Provide an arrow-pushing mechanism that rationalizes the formation of each of the products you predicted in Assessment 8.31. Make sure your mechanism accounts for all products formed, including stereoisomers and regioisomers, where applicable.

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Textbook Question

What is the expected product for the reaction of each of the following alkenes with (i) HBr and (ii) HCl?

(d)

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Textbook Question

For the enzyme isopentenyl pyrophosphate isomerase, IPP binds tightly as a result of interactions between the active site amino acid residues and the diphosphate of IPP. Without concerning yourself with the structure of amino acids, what charges might you expect to be present in the active site to hold IPP in place so that the enzymatic reactions can occur?

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Textbook Question

Draw a mechanism for the acid-catalyzed conversion of DPP to IPP. How do you know that your mechanism is correct?

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