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Dangerous Conversationalist
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 Posted: Wed Jul 17, 2013 3:43 pm
Nucleophilicity vs Basicity
Nucleophilicity is a kinetic concept - how good/fast is it at reacting? how little energy does it need to react?
Basicity - thermodynamic concept; how stable are the reactant/products? How badly soemthing would like to react
Lewis base = electron donor
F- : more basic than I-, but less nucleophilic in protic solution (H+) Fluoride wants to bond with something MORE badly than an I-. F- is less stable in that form than Br-. F- is a small ion, water can form tight shell around it, makes it harder to react in a solution
Basicity
OH- > F- > Cl- > Br- > I-
Nucleophilicity
Protic vs Aprotic
Protic
I- (best cuz not hindered by hydrogen; huge) > OH- > F-
Aprotic (basicity and nucleophilicity correlate)
OH- > F- > I-
OH- hydroxide has an extra e-, very basic molecule
Nucleophilicity how good it can get in there and make a rxn happen
Bigger molecules might make it very hard to get in (steric hindrance) to target nucleus. OH- is tiny so should be easy peesy.
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Posted: Wed Jul 17, 2013 4:49 pm
ELIMINATION
E2 reaction
Something is eliminated, 2 = both reactants are involved for the rate determining step. You create a double bond. This happens all in one step
E1 reaction
weak base ethanol
tertiary best candidate
Leaving group gets eliminated, so double bond forms
rate determining step
Zaitsev's Rule
In E2/E1 reactions, H must get swiped off B-beta carbons (alpha is the one the leaving group is on).
Which h do we take off? you will form both products, but majority will be the double bond formed by the H on the highest substituent carbon (tertiary). Others will form but minorly.
Zaitsev's Rule - Carbon that is gonna lose H+ is the one that has fewest H. OR bonded to more carbons
Why is this happening?
Hyperconjugation - the carbon after beta (not alpha other way) helps stabilize; more stable doubl ebodn will beofrm if other carbons are near hte double bond
But2-ene more liekly > than but-1-ene
I'm getting sleepy...
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Dangerous Conversationalist
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Dangerous Conversationalist
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Posted: Thu Jul 18, 2013 12:08 am
Haloalkanes - alkanes contain at least one halogen - makes good leaving group (usually involves substitiution and elimination rxns)
Formation of Haloalkanes
alkanes can be converted into haloalkanes by free radical halogenation rxn, or alcohol
Ethers
Weak bases, generally unreactive in absence of strong acids
Addition rxns to alkenes and alkynes
Addition rxns are defined by bonding changes that occur over course of a rxn; a pi bond in starting material is broken, and 2 pi bonds in product result. This is REVERSE OF ELIMINATION RXNS
Markovnikov's Addition - carbon of hte dobule bond that has most H gets another H, the most stable carbocation is formed
peroxides + Hbr makes it anti-markovnikov, will add halogen to the least substituated carbon
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Posted: Thu Jul 18, 2013 12:49 am
How to define aromaticity
Huckel numbers
4n+2
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Dangerous Conversationalist
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