Alkenes, Alkynes and Electrophilic Addition
Alkenes and alkynes have π bonds that attract electrophiles, giving addition products whose regiochemistry follows Markovnikov's rule.
What is Alkenes, Alkynes and Electrophilic Addition?
Alkenes and alkynes have π bonds that attract electrophiles, giving addition products whose regiochemistry follows Markovnikov's rule.
Key formula / rule: Markovnikov addition places the electrophile so the more stable carbocation forms.
Key points
- Apply Markovnikov's rule to predict addition products.
- Compare ionic and radical addition of HBr to an alkene.
Common exam trap
Applying the peroxide effect to HCl or HI.
Definitions
- Term
Alkenes, Alkynes and Electrophilic Addition
- Meaning
Alkenes and alkynes have π bonds that attract electrophiles, giving addition products whose regiochemistry follows Markovnikov's rule.
- Term
Alkenes, Alkynes and Electrophilic Addition — explanation
- Meaning
The π electrons are exposed and loosely held, so addition rather than substitution dominates. Markovnikov orientation follows from forming the more stable carbocation.
Learning objectives
Apply Markovnikov's rule to predict addition products.
Compare ionic and radical addition of HBr to an alkene.
Formulae
- Key point
Markovnikov addition places the electrophile so the more stable carbocation forms.
- Key point
Peroxide effect reverses orientation for HBr through a radical mechanism.
- Key point
Alkynes add two equivalents of a reagent stepwise.
Prerequisites
CHE-U4-HC-T1-S1-C1
Common mistakes
Applying the peroxide effect to HCl or HI.
Ignoring the possibility of carbocation rearrangement.
Keywords
Alkenes
Alkynes
Electrophilic
Addition
Practice preview
Consider the following reaction sequence: 1. CH3-CH=CH2 + HBr --> Product A 2. Product A + KOH (alcoholic) --> Product B 3. Product B + Br2 (CCl4) --> Product C What is the final product C?…
hard
What is the primary characteristic of alkenes and alkynes that makes them susceptible to electrophilic addition reactions?…
easy
When HBr is added to propene, CH3-CH=CH2, according to Markovnikov's rule, what is the major product formed?…
easy