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Organic Chemistry I > Radical Halogenation, Substitution, Elimination > Flashcards

Radical Halogenation, Substitution, Elimination Flashcards

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1
Q

What are the mechanism steps for an E2 reaction?

A

-convert OH 1. LG leaves, steal an ANTI beta H, form a double bond

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2
Q

What are the steps for an SNI reaction?

A

-protonate OH 1. LG Leaves, form + -Rearrange 2. Nuc Attacks -deprotonate

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3
Q

What type of solvent is preferred for SN1?

A

polar protic

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4
Q

What is the rate equation for unimolecular reactions?

A

rate = k[substrate]

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5
Q

What is the reagent for SN1?

A

Weak nuc

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6
Q

What are the 2 things to remember about bulky bases?

A
  1. Won’t do SN2 (except TBuO on methyl) 2. Favors less substituted beta H
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7
Q

What might lower the activation energy needed for an SN1 reaction?

A
  1. more stable carbocation 2. polar protic solvent
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8
Q

Which reaction does NOT have a leaving group on the substrate?

A

Radical halogenation (and acid/base)

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9
Q

What reaction will occur if there is no anti beta H available and the reagent is a strong base?

A

SN2 (only if the base is not bulky or dinky)

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10
Q

What are the bulky bases?

A

TBuO-, DBU, LDA

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11
Q

In naming what are 3 types of stereochemistry that might be included in the name?

A
  1. R/S 2. E/Z 3. cis/trans
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12
Q

What is an electrophile?

A

The thing getting attacked by the nucleophile

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13
Q

What makes a good LG?

A
  1. neutral on its own (positive when on the substrate) 2. Less basic
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14
Q

When naming alcohols, what 3 things matter in naming the parent?

A
  1. The OH must be attached to the parent 2. The OH must be at the lowest number possible on the parent 3. The OH must get a locant number (e.g. 2-pentanol or pentan-2-ol)
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15
Q

When asked to choose the reagent, what must you include in your answer?

A

Only the reagent(s) needed to form the product

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16
Q

What type of compounds/mixtures are optically inactive?

A

Achiral- no stereocenters or meso Racemic mixtures- 50/50 mix of enantiomers

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17
Q

What are the mechanism steps for an SN2 reaction?

A

-convert OH 1. LG leaves and nuc attacks -deprotonate

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18
Q

Why can an -OR with resonance NOT be considered basic?

A

Because resonance stabilizes the charge and makes it a weaker base

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19
Q

What is the template for a strong Base?

A

-OR (no resonance), -CCR (triple bond), -NR2 (not N3)

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20
Q

What is the order of cation/anion/radical stability?

A

Me

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21
Q

What is the definition of “meso”?

A

A compound with an internal plane of symmetry (two identical halves with opposite stereochemistry- think eyeglasses)

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22
Q

What are the two types of special bases?

A

Bulky and dinky

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23
Q

When asked to predict the product, what must you include in your answer?

A

Only the product with relative stereochemistry

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24
Q

What type of compounds/mixtures are optically active?

A

Chiral compounds Uneven mixtures of chiral compounds Diastereomers

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25
Q

What is the rate equation for bimolecular reactions?

A

rate = k[substrate][reagent]

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26
Q

What is the reagent for E1?

A

Strong Acids

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27
Q

How can you identify an inversion?

A

Opposite R and S

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28
Q

What is the difference between using SOCl2 and TsCl to convert OH?

A

SOCl2 (and PBr3) follows an SN2-like mechanism and therefore prefers primary OH groups and has an inversion. TsCl is not selective and does not invert

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29
Q

What are the mechanism steps for radical halogenation?

A

Initiation: form radical reagent Propogation 1: form radical substrate Propogation 2: form product with new reagent Termination: join any 2 radicals

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30
Q

When does SN2 win with a strong base reagent?

A

When the LG is primary or methyl

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31
Q

What is the template for a weak Nuc?

A

H-nuc

32
Q

What is the definition of “diastereomers”?

A

“Non-mirror images” or two compounds with only some of the stereochemistry mirrored

33
Q

Which mechanisms are concerted?

A

SN2 and E2

34
Q

Which substitution reaction leads to only ONE product?

A

SN2

35
Q

What are the mechanism steps for an E1 reaction?

A

-protonate OH 1. LG Leaves, form + -rearrange 2. Steal a beta H, form a double bond

36
Q

What is the template for a strong Acid?

A

H2SO4 and H3PO4

37
Q

How is an ether formed using substitution?

A

The oxygen stuck in the middle acted as the nucleophile

38
Q

Which reactions can rearrange?

A

SN1 and E1 (they form a carbocation)

39
Q

What is the reagent for SN2?

A

Strong nuc

40
Q

What type of solvent is preferred for SN2?

A

polar aprotic

41
Q

What are the two SN2-like substitution reagents?

A

SOCl2 and PBr3

42
Q

Which mechanisms are stepwise?

A

SN1 and E1

43
Q

What are the pairs of competing reactions?

A

SN1 and E1, SN2 and E2

44
Q

When might we form a primary carbocation?

A

When it is allylic or benzylic

45
Q

What is the reagent for E2?

A

Strong Base

46
Q

What are the 2 things to remember about dinky bases?

A
  1. Won’t do SN2 2. Can deprotonate OH
47
Q

What are the two most common no substitution reagents (for converting OH)?

A

TsCl and MsCl

48
Q

What is the definition of “enantiomers”?

A

Non-superimposable mirror images (think hands)

49
Q

What are 5 types of rearrangements? (hint: two are “normal”, two are “McCune specials, and one you learned for your first exam)

A
  1. Hydride shift 2. Methyl shift 3. ring opening 4. ring closing 5. Resonance
50
Q

When asked to propose a synthesis, what must you include in your answer?

A

Reagents and products formed in each step of the reaction

51
Q

What is the reagent for radical halogenation?

A

X2 plus light or heat

52
Q

What makes a good Nuc?

A
  1. Anionic 2. Less electronegative
53
Q

What are the 3 ways to make OH a good LG?

A
  1. protonate 2. SN2-like substitution 3. No substitution
54
Q

What are 3 polar aprotic solvents?

A

DMSO, DMF, THF, acetone, diethyl ether

55
Q

What is the template for a strong Nuc?

A

-Nuc

56
Q

What might lower the activation energy needed for an SN2 reaction?

A
  1. less substituted LG 2. polar aprotic solvent 3. strong nucleophile 4. strong leaving group
57
Q

What might cause an E1 reaction to be preferred over SN1?

A

heat

58
Q

What is the dinky base?

A

H-

59
Q

What is the definition of “achiral”?

A

A structure with a superimposable mirror image (think either a sphere or eyeglasses)

60
Q

When naming alkenes versus alkanes, what changes about the parent name?

A

suffix -ane changes to -ene (e.g. butane vs. butene)

61
Q

When asked to draw the mechanism, what must you include in your answer?

A

ALL curved arrows to show EVERY step of the mechanism

62
Q

What reactions will protonate OH?

A

SN1 and E1

63
Q

What type of solvent is preferred for E1?

A

polar

64
Q

OH + TsCl = ?

A

OTs

65
Q

What is the difference in stereochemistry with SN1/SN2 products?

A

SN1 nuc attacks both sides SN2 inverts

66
Q

What is the definition of “chiral”?

A

A structure with a non-superimposable mirror image (think hands)

67
Q

What are the selectivity factors for radical chlorination?

A

1:2:3 = 1:4:5

68
Q

How many “humps” must a unimolecular reaction have on its energy diagram?

A

2

69
Q

How many “humps” must a bimolecular reaction have on its energy diagram?

A

1

70
Q

Can an E2 reaction happen when the LG is equatorial? Why or why not?

A

No because the beta H must be anti-periplanar (i.e. anti) to the LG

71
Q

Why must we use new reagent in the P2 step of radical halogenation?

A

To generate a new halogen radical to feed back into P1

72
Q

What are the selectivity factors for radical bromination?

A

1:2:3 = 1:80:1600

73
Q

Oxygen and sulfur are often interchangeable. What is the most important difference when using them as reagents?

A

Oxygen may be basic while sulfur is not (i.e. -OH pka is 16, while -SH pka is 10)

74
Q

What type of solvent is preferred for E2?

A

Protic, often the conjugate acid of the base reagent

75
Q

What is the pka dividing line for strong bases?

A

pka > 16

76
Q

What are 3 polar protic solvents?

A

Methanol (MeOH), ethanol (EtOH), acetic acid

77
Q

Match cis/trans with E/Z

A

Cis = Z Trans = E

Organic Chemistry I (1 decks)

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