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My ORGO DAT Prep > Substitution And Elimination > Flashcards

Substitution And Elimination Flashcards

1
Q

Sn1 reactivity (from most reactive to least)

A

Based on carbocation stability:
3° benzyl
3° allyl
2° allyl
3°
1° allyl
2°

1° and methyl cannot undergo Sn1 reaction

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2
Q

Sn1 reaction product stereochemistry

A

Give racemic mixture of enaantiomers —> this is due to nucleophile being able to attack from either side

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3
Q

Do Sn1 reactions involve rearrangement?

A

YES, because they involve carbocation intermediates, the carbocation can rearrange to give the most stable carbocation intermediate

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4
Q

What is the rate of Sn1 reactions?

A

Rate = k[electrophile]

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5
Q

What is the rate for Sn2 reactions?

A

Rate = k[electrophile][nucleophile]

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6
Q

Sn2 reactivity (from most reactive to least reactive)

A

Methyl LG
1° LG
2° LG

Bezyls and allyls CAN undergo Sn2 depending on the nucleophile

3° LG cannot undergo Sn2 reactions

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7
Q

Sn2 stereochemistry

A

Inversion of stereochemistry due to backside attack

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8
Q

what mechanism would you use if a 1° carbon is bonded to the leaving group?

A

Sn2 or E2

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9
Q

what mechanism would you use if a 2° carbon is bonded to the leaving group?

A

Sn1, Sn2, E1 or E2

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10
Q

what mechanism would you use if a 3° carbon is bonded to the leaving group?

A

Sn1, E1 or E2

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11
Q

1° bonded to leaving group
strong nucleophile or weak base

A

Sn2

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12
Q

1° carbon bonded to leaving group
strong nucleophile or strong base

A

Sn2 (major)
E2 (minor)

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13
Q

1° carbon bonded to leaving group
strong, bulky base

A

E2

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14
Q

2° carbon bonded to leaving group
weak nucleophile or weak base

A

Sn1 or E1

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15
Q

2° carbon bonded to leaving group
strong nucleophile or weak base

A

Sn2

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16
Q

2° carbon bonded to leaving group
strong nucleophile or strong base

A

E2 (major, trans)
Sn2 (minor)

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17
Q

2° carbon bonded to leaving group
strong bulky base

A

E2

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18
Q

3° carbon bonded to leaving group
weak nucleophile or weak base

A

Sn1 or E1

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19
Q

3° carbon bonded to leaving group
strong nucleophile or weak base

A

Sn1

20
Q

3° carbon bonded to leaving group
strong base

A

E2

21
Q

3° carbon bonded to leaving group
strong, bulky base

A

E2 (non-zaitsev)

22
Q

What are the three trends when ranking strength of nucleophiles?

A

1) Negative charges increase nucleophilicity
2) Nucleophilicity increases going left across a row
3) Moving down a column, nucleophilicity depends on the solvent

23
Q

Strength of nucleophiles in protic solvents:

A

Increases going down a column this is because protic solvents form a “hydrogen bond web” and solvate the nucleophile, making it harder for the nucleophile to attach —> a larger atom will break through the web better than a small, solvated atom

Size matters for protic solvents

24
Q

Strength of nucleophiles in aprotic solvents:

A

Decreases going down a column because aprotic solvents do not interact with the nucleophile —> only concentrated, negative charges matter in aparotic solvents

25
Q

Strength of nucleophile going across a row:

A

Increases going left across a row (becomes more basic)

Ex: F- is a weaker nucleophile than NH2-

26
Q

In nucleophilic addition reactions, EWG substituents (increase/decrease) the positive charge on the carbonyl carbon, thus (increasing/decreasing) reactivity

A

Increase
Increasing

An EWG pulls the electron density away from the carbonyl carbon, thus making the reactivity of the nucleophile and carbon greater

27
Q

In nucleophilic addition reactions, (aldehydes/ketones) are more reactive

A

Aldehydes

28
Q

In nucleophilic addition reactions, the carbon of the carbonyl group is _____________

A

Electron deficient- the electronegative oxygen pulls electron density away from the carbonyl carbon

29
Q

In nucleophilic addition reactions, bulky substituents attached to the carbonyl carbon will (increase/decrease) steric hinderance involved with nucleophilic attack, thus (increase/decreasing) reactivity

A

Increase
Decreasing

30
Q

General rule for determining aprotic solvents:

A

Aprotic solvents lack an acidic proton, if the solvent lacks hydrogen directly bonded to oxygen or nitrogen, it can be considered aprotic

31
Q

What solvent should be used for Grignard reagents?

A

Grignard reagents are highly basic compounds that can act as a nucleophile to attack carbonyl-containing compounds. Aprotic solvents should be used with Grignard reagents because in protic solvents, the Grignard reagent will act as a base to deprotonate the solvent rather than attacking the nucleophile

32
Q

strong/weak nucleophile/base NaSCH3

A
  • strong nucleophile weak base
33
Q

strong/weak nucleophile/base NaOH

A
  • strong nucleophile strong base
34
Q

strong/weak nucleophile/base tBu-OK

A

strong base weak nucleophile

35
Q

strong/weak nucleophile/base NaSH

A

weak base strong nucleophile

36
Q

strong/weak nucleophile/base NaCN

A

weak base strong nucleophile

37
Q

strong/weak nucleophile/base H2O

A

weak base weak nucleophile

38
Q

strong/weak nucleophile/base NaH

A

strong base weak nucleophile

39
Q

a strong base would be able to ____ H atom easily

A

accept

40
Q

strong/weak nucleophile/base EtOH

A

weak nucleophile weak base

41
Q

strong/weak nucleophile/base H2S

A

strong nucleophile weak base

42
Q

strong/weak nucleophile/base MeOH

A

weak nucleophile weak base

43
Q

strong/weak nucleophile/base NaN3

A

strong nucleophile weak base

44
Q

strong/weak nucleophile/base KOH

A

strong nucleophile strong base

45
Q

strong/weak nucleophile/base KOH

A

strong nucleophile strong base

46
Q

strong/weak nucleophile/base NaI

A

strong nucleophile weak base

47
Q

strong/weak nucleophile/base NaOMe

A

strong nucleophile strong base

My ORGO DAT Prep (10 decks)

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