Ch.7
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What is the energy in pi bonds
60-65 kcal/mol
What is a degree of unsaturation
A pi bond or a ring
How do you calculate unsaturation?
Use CnH2n+2, so how many Hs you are missing and divide that by 2
Double bond Nomenclature
• Find the longest carbon chain including the double-bonded carbons • Ending changes from -ane to -ene • Number the chain so the double has the lowest possible number
In a ring, the double bond is assumed to be in between carbon ___ and _____
carbon 1 and 2
Cis vs. Trans double bond
Cis: Both constituents are on the same side of the bond Trans: Both constituents are on the opposite side of the bond
When are trans cycloalkenes stable
When the ring has at least 8 carbons
Determining E and Z
Number substituents according to atomic number If groups are on opposite sides it’s E, if they are on the same size it’s Z
Lower heat of hydrogenation means a chemical is ____ stable
more
Bredt’s Rule
A bridged, bicyclic compound cannot have a double bond at a bridgehead positioin unless one of the rings contains at least eight carbon atoms
What drives elimination reactions
Strong or weak bases
How many groups are lost during an E1 Reaction
A hydrogen and a Halide
A ________ acts as a base
Nucleophile
E1 has the same conditions as ______
SN1
E1 Rate Law
k[electrophile]
Do you go through carbocations with E1
Yes! so you can still form SN1 products
E1 forms the _____ stable alkenes because of the __-rule
most stable Z-rule
For E1 use a ______ and a ______ electrophile
Weak base tertiary electrophile
Does E1 product both cis and trans products
Yes
Zaitsev’s Rule
If more than one elimination product is possible, the most substituted alkene is the major product
E2 happens in ____ step(s)
one step; the proton is removed, the double bond forms, and the leaving group leaves all in one step
E2 needs _______ orientation
Antiperplanar (cis)
E2 order of reactivity
3º > 2º > 1º
Hoffmann Orientation
Formed by bulky bases, The least stable alkene (the one with the least number of substituents on the carbons of the double bond) is formed