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Allylic and Allyl
Carbon atom connected to a double bond
Reactive Intermediates
Cation (+), Radical (.), anion (-)
Anti-bonding orbital
Side by side parralel p orbitals but opposite signs--HIGH ENERGY
Non-bonding orbital
3 carbon atoms but the parallel p orbitals are seperated by a non bonding carbon--Mid Energy
Allylic Properties
More acidic, SN1 rxns and radical reactions -- Use of NBS and NCS
Isolated-no added stability, Conjugated-more stable
Conjugated Diene
Bond length of sigma bond is shorter than normal because of hybridization
\\\"p\\\" Character (ie. csp2 - 33%s , 67% p)
More \\\"p\\\" character is a weaker bond
Room Temp Energy
18-20 Kcal/Mol
1,2 addition vs. 1,4 addition
1,2 addition- kinetic product (more stable intermediate) 1,4 addition-thermodynamic product (more stable final product)
Double Bond Location
Internal double bond is more stable than terminal double bond
Diels Alder Rxn (4+2 rxn)
Concerted mech.-steriochemistry does not change, Diene attacks dienophile
Endo Rule
Endo product favored electron withdrawing groups want to be closest to the pi system and steric trouble lead to endo product
place where electrons can\\\'t interact (due to opposite signs) nodes make molecule less stable
Benzene bond length
C-C bonds are between a sigma and pi bond length
Aromatic Molecule Requirements
Must be cyclic with delocalization over entire system, must be planar, must have parallel p orbitals (fully conjugated) and must follow 4n+2 rule
Less stable as a cyclic molecule then straight chain
Equally as stable in cyclic molecule as straight chain
More stable than straight chain
Huckle\\\'s Rule
Aromatic must have 4n+2 pi electrons (2 electrons per pi bond). 4n+2 rule gives full bonding orbitals
Annulene Naming
Benzene= [6]-annulene
Important pKas
Alkane-50, Alkene-40, Hydrogen-35, Alkyne-25, Alcohol-18, water-16, carboxylic acid-5
Higher pKb=weaker Base
Pi and Sigma Bonds
Pi bonds are weaker and more accessible for rxns than sigma bonds
Electrophilic Aromatic Substitution (EAS)
2 step process-1st step rate determining because interupts aromaticity. Need unstable electophile with full blown positive charge
Benzesulfonic Acid
Benzene w/ SO3H
Isopropyl Benzene
Benzene w/ isopropyl
Benzene w/ methyl
Benzene w/ NH2
Benzene w/ NO2
Benzene w/ OH
Ortho, Meta and Para
Ortho-1,2 subst. Meta-1,3 subst, Para-1,4 subst.---ONLY FOR DI SUBSTITUTED BENZENE
If G(group attached to ring)
If G is electron donating it ACTIVATES the ortho and para positions--FASTER RXN than benzene
If G(group attached to ring)
If G is electron withdrawaling it DEACTIVATES the ortho and para positions--leading to meta position---SLOWER RXN than benzene
Activating Groups
Inductive donation-Alkyl Groups-donate electron density through sigma bond based on proximety, Resonance Donatating-Atom with a lone pair of electrons-OH, NH2, OR--MUCH stronger effect
Halogens are Electron WITHDRAWLING
because of poor orbital overlap due to size difference between rows
Electron Withdrawling Examples
NH3(+), CF3, NO2, Carbonyl
2 groups attached to benzene
Activator ALWAYS wins over Deactivator, Strength of the activator MATTERS
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