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ACS STUDY > Elementary Steps and Mechanisms > Flashcards

Elementary Steps and Mechanisms Flashcards

1
Q

Which elementary step is pictured?

A

Nucleophilic Addition

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2
Q

Which carbocation is least stable?

methyl, 1º, 2º, 3º

A

methyl carbocation

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3
Q

Which carbocation is most stable?

methyl, 1º, 2º, 3º

A

3º carbocation

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4
Q

In an SN1 reaction is it stereospecific (only get R OR S not both) or will you get racemization (get both R AND S)?

A

An SN1 reaction will give you both R and S stereoisomers

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5
Q

Will adding heat favor substitution(SN1/SN2) or elimination(E1/E2)?

A

Adding heat will favor elimination pathways

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6
Q

In an E2 reaction do you get both E AND Z stereoisomers or do you only get one (E OR Z)?

*If you get both, which stereoisomer is favored?

*If you only get one, why?

A

You get one or the other (E or Z)

In an E2 reaction the leaving group and the H that are eliminated must be 180º away from eachother (anti)

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7
Q

Is ethanol a protic or aprotic solvent?

A

protic

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8
Q

Which elementary step is pictured?

A

Electrophile Addition

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9
Q

How do you classify a base as “weak”?

A

It must be weaker than -OH

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10
Q

Does a weak base promote E1 or E2?

A

weak bases promote E1

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11
Q

For an elementary step with a negative delta Gº will the transition state resemble reactants or products?

A

It will favor reactants

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12
Q

Is acetone a protic or aprotic solvent?

A

aprotic

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13
Q

Does nucleophile concentration effect the rate of SN1/E1 reactions?

A

No

SN1/E1 reactions ar eonly dependent on substrate concentration

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14
Q

Does a strong base promote E1 or E2?

A

Strong bases promote E2

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15
Q

Is DMF a protic or aprotic solvent?

A

aprotic

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16
Q

Which elementary step is pictured?

A

Proton Transfer

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17
Q

If your substrate is 3º (tertiary) - which reactions will it favor (or which will it not favor)?

(SN1/SN2/E1/E2)

A

it will not favor SN2

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18
Q

Do polar protic solvents favor SN1/E1 or SN2/E2?

A

polar protic solvents favor SN1 and E1

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19
Q

Which elementary step is pictured?

A

E2

Bimolecular Elimination

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20
Q

When will a reaction (SN1, SN2, E1, or E2) occur?

If the Carbon bonded to the leaving group is sp, sp2, or sp3 hybridized?

A

SN1, SN2, E1, or E2 can only occur if the carbon bonded to the leaving group is sp3 hybridized

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21
Q

What will the rate determining step correlate with on a reaction energy diagram?

A

It will correlate with the highest free energy point on the diagram

22
Q

If your substrate is methyl - which reactions will it favor?

(SN1/SN2/E1/E2)

A

methyl favors SN2

23
Q

What is a polar protic solvent?

A

A solvent that has the ability to be a hydrogen bond donor (i.e. can donate H’s)

24
Q

Is H2O a protic or aprotic solvent?

25
Which elementary step is pictured?
Coordination
26
What is a polar aprotic solvent?
A solvent that can only accept H's - it can not donate them
27
Is DMSO a protic or aprotic solvent?
aprotic
28
Does a weak nucleophile promote SN1 or SN2?
Weak nucleophiles promote SN1
29
Does a strong nucleophile promote SN1 or SN2?
Strong nucleophiles promote SN2
30
How do you classify a base as "strong"?
It must be at least as strong as -OH
31
In an E1 reaction do you get both E **AND** Z stereoisomers or do you only get one (E **OR** Z)? \*If you get both, which stereoisomer is favored? \*If you only get one, why?
You get both E and Z \*the most stable isomer is preferred
32
Which elementary step is pictured?
Heterolysis
33
If your substrate is 2º (secondary) - which reactions will it favor? (SN1/SN2/E1/E2)
it will favor all | (SN1/SN2/E1/E2)
34
Does nucleophile concentration effect the rate of SN2/E2 reactions?
Yes SN2/E2 reaction rates are dependent on both nucleophile and substrate concentrations
35
For an elementary step with a positive delta Gº will the transition state resemble reactants or products?
It will favor products
36
Is formamide a protic or aprotic solvent?
protic
37
Which elementary step is pictured?
Nucleophile Elimination
38
In an SN2 reaction is it stereospecific (only get R **OR** S not both) or will you get racemization (get both R **AND** S)?
SN2 reactions are stereospecific- you will get the opposite steroisomer
39
If your substrate is 1º (primary) - which reactions will it favor? (SN1/SN2/E1/E2)
1º substrates favor SN2 and E2 (benzyl and allyl carbons will favor SN1 and E1)
40
Which carbocation will have the slowest reaction rate? methyl, 1º, 2º, 3º
methyl carbocation
41
Which elementary step is pictured?
E1
42
Which elementary step is pictured?
Carbocation rearrangements
43
What is the rate determining step for an SN1 reaction?
heterolysis
44
Which elementary step is pictured?
Electrophile Elimination
45
Which carbocation will have the fastest reaction rate? methyl, 1º, 2º, 3º
3º carbocation
46
Which elementary step is pictured?
SN1
47
Do polar aprotic solvents favor SN1/E1 or SN2/E2
polar aprotic solvents favor SN2/E2
48
Which elementary step is pictured?
SN2 Bimolecular Substitution
49
Is acetonitrile a protic or aprotic solvent?
aprotic
50
elimination with a (regular) base will prefer the less or more substituted alkene?
elimination usually takes place to favor the most highly subsituted alkene
51
elimination with a big, bulky base will prefer the less or more substituted alkene?
it will prefer the less highly substitued alkene
52

ACS STUDY (13 decks)

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