What is the range of UV absorption for conjugated compounds?
200-400 nm
Properties of Conjugated Dienes: Bond length
shorter single bond
Properties of Conjugated Dienes: Stability
the less heat of hydrogenation, the greater the stability
_____ S character, ______ stability
greater, greater
does increased energy mean more or less stable?
less stable with less Pi interaction
at or below room temperature
the 1,2 product predominates over the 1,4 product
at higher temperatures
the 1,4 adduct prodominates
which product is the 1,2-adduct?
Kinetic Product
which product is the 1,4-adduct?
Thermodynamic Product
Rules for 1,2 Product shortcut with H2O and H3O+
1) Add H on C1
2) Add OH on C2
3) Delete double bond between C1-C2
4) Keep double bond between C3-C4
Rules for 1,4 Product shortcut with H2O and H3O+
1) Add H on C1
2) Add OH on C4
3) Delete both double bonds
4) Form a double bond between C2-C3
Rules for 1,2 Product shortcut with Br2
1) Add Br to C1
2) Add Br to C2
3) Delete double bond between C1-C2
4) Keep double bond between C3-C4
Rules for 1,4 Product shortcut with Br2
1) Add Br on C1
2) Add Br on C4
3) Delete both double bonds
4) Form double bond on C2-C3
examples of Electron Donating Groups (EDG)
alkyl groups, alkoxy, ester (OCOR), amines (NH2, NHR, NR2), benzene, OH
examples of Electron Withdrawing Groups (EWG)
aldehyde, ketone, carboxylic acid, ester (CO2R), nitrile (C triple bond N), nitro
dienes prefer to be electron ____
rich
dienophiles prefer too be electron _______
poor
if the dienophile possesses an electron-withdrawing substituent, the Diels-Alder reaction takes place at ________ ________
high speed
example of non-aromatic ring
cyclooctaetraene
Electron Donation Scale “Point of Origin”
Hydrogen
do electron-withdrawing groups make dienophiles faster or slower?
Faster
do electron-donating groups make dienes faster or slower?
Faster
What does the strongest EWG called and what does it lack?
Ammonium cation (NR3), lone pair
What does the strongest EDG have?
A lone pair on N (NH2)
