allylic position

Problem # 1281

Allylic and benzylic halides tend to undergo both SN1 and SN2 substitution reactions at a faster rate than their alkyl counterparts.

For example, both allyl chloride and benzyl chloride undergo SN2 reaction at a faster rate than propyl chloride. 

The same holds true for SN1 reactions: a 2° allyl or benzyl halide undergoes SN1 reaction faster than a 2° alkyl halide. Explain.

MS 909 - Conjugated Dienes and the Allyl Position Submitted by Matt on August 6, 2011.

Textbook and Chapter: Carey and Giuliano 8th Ed. (2010), Chapter 10

Keywords: allylic position, conjugate addition

Description: Covers topics related to the allyl position and conjugated dienes:

  • Allyl cation, anion, and radical resonance forms
  • What conjugated dienes can or can't undergo Diels-Alder reactions
  • Allylic brominations using N-bromosuccinimide (NBS)
  • 1,2 and 1,4 additions (thermodynamic vs kinetic conditions)

Total Problems: 4

Problem # 581

Draw all products for the two reactions below.

The allylic alkene gives two products- the 1,2 product, and the 1,4 product. 

However, the benzylic alkene only gives the one product (analogous to the 1,2 product), instead of multiple products (like the 1,4 product, 1,6 product, and 1,8 product). Why is this the case?

Problem # 572

Let's work through a conjugate addition problem.

Write out the mechnanism for the formation of the 1,2 and 1,4 products of the reaction below.

Problem # 571

Write the structure of the major organic product of each reaction.

Problem # 569

Draw all resonance forms for each species. 

For the anion and cation species, used curved arrows. For the radical species, use hooks.