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one element of unsaturation corresponds to what?
- a saturated hydrocarbon
-a saturated hydrocarbon with oxygen
- a saturated hydrocarbon with nitrogen
either a ring or a double bond, not both
- - CnH2n+2
- - CnH2n+2O
- - CnH2n+3N
Structure of :
- a methylene alkyl group
- a vinyl alkyl group (aka: ethenyl)
- an allyl group (aka: 2-propenyl)
__ groups are double bonds fused to rings
Explain E and Z prioritizing
What do you do if you have multiple bonds?
- E double bond (higher priority groups are on opposite sides
- Z double bond (higher priority groups are n the same side)
if its a double bond, act like its bonded to the atom twice; if triple, three times
If a double bond is in the ring, it is __.
If you have a nine carbon ring with one double bond, but the hydrocarbon has multiple double bonds, what do you do?
take the longest chain containing all of the double bonds
__ helps to determine stability.
What is hydrogenation of alkenes? What does the energy difference lie in? If the energy difference is lower, what does that mean?
adding H across the pi bond, saturating it
- lie in the stability of the product; in the difference of reactants
- it's lower in energy
__ is more stable than __.
Explain relative stabilities in terms of substitution?
What is hyperconjugation?
pi bond associates with an adjacent C-H signma bond
Explain the Addition Reaction
- - attack of the pi bond on the electrophile forms a carbocation
- - attack by a nucleophile gives the product of addition
Explain the HBr addition
- 1) protonation of the double bond forms a carbocation
- 2) bromide ion attacks the carbocation
- -- The electrophile HBr is attacked by the pi bond electrons of the double bond, and a new C-H sigma bond is formed. This leaves the other carbon atom with a + charge and a vacant p orbital
- --Br- donates an electron pair to the positively charged carbon atom, forming a C-Br sigma bond and yielding a neutral addition product
__ is determined by stability of the intermediate.
the addition of H-X across a pi bond results in the more highly subbed alkyl halide as the major product
tertiary > secondary > primary > methyl
two constitutional isomers that could result from an addition reaction
only one regioisomer forms at the expense of the other
both regioisomers are formed, but one is formed in preference
When will rearrangements occur?
Endo transition state looks like __
Exo transition state looks like __.
to stabilize the carbocation
What is Hammond's Postulate
related species that are close in energy are close in structure
in an endothermic rxn, the TS is similar to the product in structure and stability
In an exothermic reaction, the transition state is similar to the reactant in structure and stability
the structure of the TS resembles the structure of the most stable species
__ rxns allow us to make double bonds
First step of addition?
What determines the product?
if you have an asymmetric alkene, the more highly subbed will be formed
protonation (the H is taken by the electrons of the double bond)
What is the rate-determining step in an addition rxn?
protonation becuase you're going from stable to high energy
- one product forms; the other doesnt
- - the more carbons there are, the more overlap there is
When will E/Z prioritizing not occur?
When we can form two products, we call it __.
Regioselective vs. Regiospecific?
if there are same groups on the same carbon
regioselective: one was preferred over another, but still a mix was made; two products form
regiospecific: one product forms
- if the double bond has equal substitutions and you want to find how it happened, what do you do?
- when will a shift occur?
For these reactions, you are going straight through __. Why?
- propose a mechanistic pathway
- in favor of the more stable carbocation
- becuase product is being removed as it forms; no Sn1 competition