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26 Cards in this Set

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  • Back
General formula for saturated hydrocarbon
saturated hydrocarbon
Give the relative energies for all Newman projections of an alkance and state their abs and relative maxs and mins
Relative energies
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
Why are cyclopropane and cyclobutane less stable than cyclo pentanes are heavier?
Because the But/propane has ring strain forcing their sp3 hybridized bonds into 90/60 degree angles, far from the ideal 109
What is the formula for hydrocarbon combustion?

What does it require?
High temp and available oxygen
Describe the 5 steps of free-radical halogenation of alkanes
free-radical halogenation of alkanes
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
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
Why is ortho-nitrophenol boil faster than para-nitrophenol
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
Which is more acidic: para nitrophenol or para methoxyphenol?
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)
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
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
What kind of solvent is favored by sn2 rxn's?
Polar, non-hydrogen bonding solvents
Describe the sn1 reaction of t-butanol with hydrobromide

What is the rate?
Is there a carbocation formed?
Is there regioselectivity?
Sn1
What type of solvent is favored by Sn1 and why?
Hydrogen bonding solvents because they stabilize the carbocation
What type of R-OH (3,2,1) favors Sn1?

Why?
3>2>1
because the carbocation is most stable on 3
Resonance structures cannot be drawn through __________
Truly sp3 carbons
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
Why do cyclobutanes and cyclopropanes undergo hydrogenation but cyclopentanes/hexanes don't?
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
Why does a 1,2 hydride or methide shift occur?
To stabilize a carbocation.
Alkene + alkyl halide
More substituted carbocation forms (2nd will form before primary)

Then rearrgangement (to tert)and then/ or halide addition
Alkene + peroxide + alkyl halide
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)
Alkene + H2SO4 + H2O
Forms carbocation with rearrangements, so -OH adds to most substituted C
Is there a carbon substitution preference for E1 vs E2 reactions?
E1 will work with 3 and some 2ndary Carbons BUT NOT PRIMARY

E2 is 3>2>1
Is there a product preference for E1 and E2 reactions?
E1 forms more substituted product and E2 forms has anti arrangement
How can you use pKa to determine a good leaving group?
The lower a pKA is of the conjugate acid, the better leaving group it is