Radical Halogenation, Substitution, Elimination

Question 1

What are the mechanism steps for an E2 reaction?

Answer 1

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

Question 2

What are the steps for an SNI reaction?

Answer 2

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

Question 3

What type of solvent is preferred for SN1?

Answer 3

polar protic

Question 4

What is the rate equation for unimolecular reactions?

Answer 4

rate = k[substrate]

Question 5

What is the reagent for SN1?

Answer 5

Weak nuc

Question 6

What are the 2 things to remember about bulky bases?

Answer 6

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

Question 7

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

Answer 7

1. more stable carbocation 2. polar protic solvent

Question 8

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

Answer 8

Radical halogenation (and acid/base)

Question 9

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

Answer 9

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

Question 10

What are the bulky bases?

Answer 10

TBuO-, DBU, LDA

Question 11

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

Answer 11

1. R/S 2. E/Z 3. cis/trans

Question 12

What is an electrophile?

Answer 12

The thing getting attacked by the nucleophile

Question 13

What makes a good LG?

Answer 13

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

Question 14

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

Answer 14

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)

Question 15

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

Answer 15

Only the reagent(s) needed to form the product

Question 16

What type of compounds/mixtures are optically inactive?

Answer 16

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

Question 17

What are the mechanism steps for an SN2 reaction?

Answer 17

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

Question 18

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

Answer 18

Because resonance stabilizes the charge and makes it a weaker base

Question 19

What is the template for a strong Base?

Answer 19

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

Question 20

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

Answer 20

Me

Question 21

What is the definition of “meso”?

Answer 21

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

Question 22

What are the two types of special bases?

Answer 22

Bulky and dinky

Question 23

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

Answer 23

Only the product with relative stereochemistry

Question 24

What type of compounds/mixtures are optically active?

Answer 24

Chiral compounds Uneven mixtures of chiral compounds Diastereomers

Question 25

What is the rate equation for bimolecular reactions?

Answer 25

rate = k[substrate][reagent]

Question 26

What is the reagent for E1?

Answer 26

Strong Acids

Question 27

How can you identify an inversion?

Answer 27

Opposite R and S

Question 28

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

Answer 28

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

Question 29

What are the mechanism steps for radical halogenation?

Answer 29

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

Question 30

When does SN2 win with a strong base reagent?

Answer 30

When the LG is primary or methyl

Question 31

What is the template for a weak Nuc?

Answer 31

H-nuc

Question 32

What is the definition of "diastereomers"?

Answer 32

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

Question 33

Which mechanisms are concerted?

Answer 33

SN2 and E2

Question 34

Which substitution reaction leads to only ONE product?

Answer 34

SN2

Question 35

What are the mechanism steps for an E1 reaction?

Answer 35

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

Question 36

What is the template for a strong Acid?

Answer 36

H2SO4 and H3PO4

Question 37

How is an ether formed using substitution?

Answer 37

The oxygen stuck in the middle acted as the nucleophile

Question 38

Which reactions can rearrange?

Answer 38

SN1 and E1 (they form a carbocation)

Question 39

What is the reagent for SN2?

Answer 39

Strong nuc

Question 40

What type of solvent is preferred for SN2?

Answer 40

polar aprotic

Question 41

What are the two SN2-like substitution reagents?

Answer 41

SOCl2 and PBr3

Question 42

Which mechanisms are stepwise?

Answer 42

SN1 and E1

Question 43

What are the pairs of competing reactions?

Answer 43

SN1 and E1, SN2 and E2

Question 44

When might we form a primary carbocation?

Answer 44

When it is allylic or benzylic

Question 45

What is the reagent for E2?

Answer 45

Strong Base

Question 46

What are the 2 things to remember about dinky bases?

Answer 46

1. Won't do SN2 2. Can deprotonate OH

Question 47

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

Answer 47

TsCl and MsCl

Question 48

What is the definition of "enantiomers"?

Answer 48

Non-superimposable mirror images (think hands)

Question 49

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

Answer 49

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

Question 50

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

Answer 50

Reagents and products formed in each step of the reaction

Question 51

What is the reagent for radical halogenation?

Answer 51

X2 plus light or heat

Question 52

What makes a good Nuc?

Answer 52

1. Anionic 2. Less electronegative

Question 53

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

Answer 53

1. protonate 2. SN2-like substitution 3. No substitution

Question 54

What are 3 polar aprotic solvents?

Answer 54

DMSO, DMF, THF, acetone, diethyl ether

Question 55

What is the template for a strong Nuc?

Answer 55

-Nuc

Question 56

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

Answer 56

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

Question 57

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

Answer 57

heat

Question 58

What is the dinky base?

Answer 58

H-

Question 59

What is the definition of "achiral"?

Answer 59

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

Question 60

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

Answer 60

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

Question 61

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

Answer 61

ALL curved arrows to show EVERY step of the mechanism

Question 62

What reactions will protonate OH?

Answer 62

SN1 and E1

Question 63

What type of solvent is preferred for E1?

Answer 63

polar

Question 64

OH + TsCl = ?

Answer 64

OTs

Question 65

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

Answer 65

SN1 nuc attacks both sides SN2 inverts

Question 66

What is the definition of "chiral"?

Answer 66

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

Question 67

What are the selectivity factors for radical chlorination?

Answer 67

1:2:3 = 1:4:5

Question 68

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

Answer 68

2

Question 69

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

Answer 69

1

Question 70

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

Answer 70

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

Question 71

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

Answer 71

To generate a new halogen radical to feed back into P1

Question 72

What are the selectivity factors for radical bromination?

Answer 72

1:2:3 = 1:80:1600

Question 73

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

Answer 73

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

Question 74

What type of solvent is preferred for E2?

Answer 74

Protic, often the conjugate acid of the base reagent

Question 75

What is the pka dividing line for strong bases?

Answer 75

pka \> 16

Question 76

What are 3 polar protic solvents?

Answer 76

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

Question 77

Match cis/trans with E/Z

Answer 77

Cis = Z Trans = E