Chapter 17 Flashcards
(14 cards)
conjugated dienes
continuous system of overlapping pi bonds
preparation of conjugated dienes
from allylic halides via elimination or dihalides via 2 elimination reactions
preparation of conjugated dienes - reagants
bulky bases to prevent SN2 reactions
stability - bonds
conjugated are more stable
equilibrium conformation
trans conformation
Electrophilic addition of dienes
addition of HX
produces 2 products 1,2 and 1,4 adducts
Electrophilic addition - production of 2 products
first is produced normally, second is produced via resonance structure
Bromination of diene
produces 1,2 and 1,4 adducts
addition of BR molecules
Diels - Alder reactions
2 carbon bonds are formed simultaneously
favoured by moderate temps
Diels - Alder reactions - high temps
disfavours products
achieves reverse diels alder reaction (breaks compound in 2)
Dienophile - substituents
adding substituents causes reaction to occur more rapidly
Diene - Diels alder reaction
must be cis configuration
if it can be in cis form wont react
Endo
syn to the larger bridge
electron withdrawing substituents occupy endo
highly favoured
Exo
anti to large bridge