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26 Cards in this Set
- Front
- Back
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General formula for saturated hydrocarbon
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saturated hydrocarbon
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Give the relative energies for all Newman projections of an alkance and state their abs and relative maxs and mins
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Relative energies
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Which is more stable axial or equatorial bond?
Where should large groups go, equatorial or axial? |
equatorial bond energy is lower because not as crowded
Large groups are more stable of equatorial |
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Why are cyclopropane and cyclobutane less stable than cyclo pentanes are heavier?
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Because the But/propane has ring strain forcing their sp3 hybridized bonds into 90/60 degree angles, far from the ideal 109
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What is the formula for hydrocarbon combustion?
What does it require? |
High temp and available oxygen
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Describe the 5 steps of free-radical halogenation of alkanes
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free-radical halogenation of alkanes
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Sp3 to Sp2
Forms both R and S depending on whether halogen came from top or bottom |
Describe orbital change for free radical halogenation of alkane and orientation of R-X
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Describe regioselection of free radical halogenation of alkane for bromination and chloronation
Which is faster, why? |
regioselection
Chloronation is faster because it is highly exoterminc (-H) for both propogation steps. Bromination is exothermic only in 1 |
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Why is ortho-nitrophenol boil faster than para-nitrophenol
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Para-nitrophenol has the OH at the para end, allows more space for intermolecular interaction
Ortho has intramol. interaction with nitro group, less H bonding means lower bp |
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Which is more acidic: para nitrophenol or para methoxyphenol?
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Para-nitro phenol
Nirto para is E withdrawing and stablaizes the better because the resonance structure keeps the charges close together (close seperation of charges is better if they exist at all) |
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Describe the Sn2 rxn of butanol with hydrobromide
what is the rxn rate? Does a carbocation form? Is there regioselection? |
The strong acid causes -OH, a poor leaving group, to become protonated, -OH2 which is a good leaving group (H20)
Rxn rate = k [nuc][elec] = k [Br-][R-OH] (depends on both hence sn"2" A carbocation never forms There is complete stereochemical inversion, R->S |
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What is the reactivity order of R-OH's in sn2? (ter, sec, and prim)
Why? |
1>2>>3
Due to steric hindress to backside attack |
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What kind of solvent is favored by sn2 rxn's?
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Polar, non-hydrogen bonding solvents
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Describe the sn1 reaction of t-butanol with hydrobromide
What is the rate? Is there a carbocation formed? Is there regioselectivity? |
Sn1
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What type of solvent is favored by Sn1 and why?
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Hydrogen bonding solvents because they stabilize the carbocation
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What type of R-OH (3,2,1) favors Sn1?
Why? |
3>2>1
because the carbocation is most stable on 3 |
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Resonance structures cannot be drawn through __________
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Truly sp3 carbons
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In the rotation around a sigma bond, between what stages is the greatest change in potential energy?
What point is the greatest PE? |
Between gauche staggered -> gauche eclipsed -> gauche staggered
Gauche eclipsed is the most unstable and thus highest PE |
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Why do cyclobutanes and cyclopropanes undergo hydrogenation but cyclopentanes/hexanes don't?
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Cyclobu/propanes have ring strain which make them unstable and suseptible to hydrogenation.
No ring stain (or very little for pentane) doesn't undergo hydrogenation |
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Why does a 1,2 hydride or methide shift occur?
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To stabilize a carbocation.
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Alkene + alkyl halide
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More substituted carbocation forms (2nd will form before primary)
Then rearrgangement (to tert)and then/ or halide addition |
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Alkene + peroxide + alkyl halide
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Peroxide undergoes homolytic cleavage R-O. + R-O.
Makes halide radical R-O. + H-Br > R-OH + B. Anti-Markovnikov Rule, halide radical adds to lowest substituted C (usually primary, but 2nd can) |
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Alkene + H2SO4 + H2O
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Forms carbocation with rearrangements, so -OH adds to most substituted C
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Is there a carbon substitution preference for E1 vs E2 reactions?
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E1 will work with 3 and some 2ndary Carbons BUT NOT PRIMARY
E2 is 3>2>1 |
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Is there a product preference for E1 and E2 reactions?
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E1 forms more substituted product and E2 forms has anti arrangement
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How can you use pKa to determine a good leaving group?
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The lower a pKA is of the conjugate acid, the better leaving group it is
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