Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
19 Cards in this Set
- Front
- Back
|
What is the reactivity in terms of methyl, primary, secondary, tertiary for SN2 reactions?
|
methyl > 1 > 2 > 3
|
|
|
What is the reactivity in terms of methyl, primary, secondary, tertiary for SN1 reactions?
|
3 > 2 > 1 > CH3
|
|
|
What is the RDS of an SN1 reaction?
|
Formation of the carbocation
|
|
|
What is the rate equation for an SN1 reaction? How can it be increased?
|
k*[haloalkanes]
Better leaving group-->quicker rate Tertiary carbons are more stable Carbocations |
|
|
Do SN1 reactions prefer a protic or an aprotic solvent? Why?
|
Protic
Stabilizes carbocation (less energy required to reach TS1) |
|
|
Do SN2 reactions prefer a protic or an aprotic solvent? Why?
|
Aprotic
Protic solvents would stabilize charges on nucleophiles, thus requiring greater activation energy |
|
|
Give examples of polar protic solvents.
|
ROH, H2O
|
|
|
Give examples of polar aprotic solvents.
|
DMSO, DMF, acetone
|
|
|
What kind of base does an E1 reaction require?
|
Weak base
|
|
|
What kind of base does an E2 reaction require?
|
Strong base
|
|
|
Describe the stereochemistry of SN1 reactions.
|
Since carbocation is sp2 (planar) then ROH can attack from either side and both enantiomers will be formed
|
|
|
Describe the reactivity in terms of methyl, primary, secondary, tertiary for E2 reactions.
|
3 > 2 > 1
|
|
|
What is the equation for rate in E2 reactions?
|
k*[haloalkanes]*[base]
|
|
|
What are the spatial requirements for bases and beta-hydrogens in E2 reactions?
|
Beta-H pulled off by base must be anti to LG in Newman projection
In cyclohaloalkanes, X & beta-C must be trans-diaxial (If disubstituted and have bulky equitorial: E2 really slow or won't happen) In cyclopentanes (for example), H must be TRANS to halogen. |
|
|
Describe how you would determine whether a reaction were SN1, SN2, E1 or E2.
|
1) Look at haloalkane-C
If primary: SN2/E2 Look at nucleophile/base: If weak base, good nucleophile: SN2 If strong, small base: Primary UNbranched: SN2 Primary Branched: E2 Major If bulky, strong (hindered) base: E2 If secondary: Look at nuc/base Wk base, good nuc: SN2 Strong, small base: E2 (major) Strong bulky base: E2 Weak nuc: SN1, E1 Tertiary: E2, SN1, E1 Weak nuc: SN1/E1 Weak base, good nuc: SN1 (major) Strong base: E2 |
|
|
What are some examples of weak bases that are good nucleophiles?
|
I-, Br-, Cl-, RS-, N3-, RC=O-, PR3
|
|
|
What are some examples of strong small bases?
|
-OH, RO-, NH2-, R2N-
|
|
|
What are some examples of strong bulky bases?
|
(CH3)3-CO-; Li+(CH3)3NC(CH3)3- (LDA)
|
|
|
What are some examples of weak nucleophiles?
|
H2O, ROH
|
