Elimination Reaction

Question 1

In an ___________ reaction a proton from the Beta position is removed with the leaving group to form a double bond

Answer 1

Elimination

Question 2

The product of an elimination reaction will always have a ________ & be a _________

Answer 2

Double bond, alkene

Question 3

Alkenes are named the same way as alkanes but end in _______

Answer 3

“ene”

Question 4

When naming alkenes have to make sure what?

Answer 4

That the longest parent chain includes the double bond & that the double bond has the lowest possible number

Question 5

Alkenes are also classified by their _______________

Answer 5

Degree of substitution

Question 6

Degree of Substitution

Answer 6

Refers to the number of akyl groups connected to a double bond (Monosubstituted - tetrasubstituted)

Question 7

Bredt’s Rule

Answer 7

States that its not possible for a bridgehead carbon of a bicyclic compound to have a double bond if it involves a trans configuration in a small ring

Question 8

Bridge bicyclic compounds can only have a double bond at a bridgehead position if one of the rings has at least ___________

Answer 8

Eight Carbons

Question 9

Cis & Trans is used to compare ______ similar group on a carbon where E & Z is used when comparing _______

Answer 9

One, two or more

Question 10

Cis alkenes are __________ than trans alkenes because it experience steric strain from being on the same plane

Answer 10

Less stable

Question 11

Alkenes are more stable when they are _____________

Answer 11

High substituted like tetrasubstituted alkenes

Question 12

____________ are products of an elimination reaction

Answer 12

Alkenes

Question 13

What are the two core steps in an elimination reaction ?

Answer 13

1. Proton Transfer
2. Loss of leaving group

Question 14

In a ___________ a base takes a proton & the leaving group leaves at the same time

Answer 14

Concerted Reaction

Question 15

In a ______________ 1st the leaving group leaves & then the base takes a proton

Answer 15

Stepwise reaction

Question 16

The ______ mechanism is the concerted reaction

Answer 16

E2

Question 17

How is an E2 reaction similar to SN2 reactions?

Answer 17

Its biomolecular where the rate law is R =k [substrate][base] (rate depends on both the substrate & base)

Question 18

__________ substrates favors E2 reactions because with steric hindrance it prevents a reagent from functioning as a nucleophile (like in SN2) at a fast rate but the reagent can still function as a base (E2) without encountering much steric hindrance

Answer 18

Tertiary Substrates

Question 19

The E_a in an E2 reaction is smallest with ________ substrate & largest with primary substrate because its least favored

Answer 19

Tertiary

Question 20

Regiochemistry

Answer 20

When the beta (β) position aren’t identical (one may be on a methyl the other may be on an ethyl) which will result in multiple products being formed where the more substituted one is the major one

Question 21

The more susbtituted product (the major product) is called what?

Answer 21

Zaitsev product

Question 22

Hofman product

Answer 22

The less substitutted alkene (minor product)

Question 23

When stereically hindered bases are used in an E2 reaction the ___________ is the major product

Answer 23

Hofman product (A base can be used to control the product of an E2 reaction)

Question 24

When there are two stereoisomer (cis or trans) as the product in an E2 reaction then the _______ will be the major product

Answer 24

Trans

Question 25

Coplanar

Answer 25

When the atoms are on the same plane

Question 26

Anti-coplanar (anti-periplanar)

Answer 26

Forms a staggered newman projection

Question 27

Syn-coplanar (Syn-periplanar)

Answer 27

Forms an eclipsed newman projection

Question 28

E2 reaction has to be in ____________ conformation to react

Answer 28

Anti-periplanar (Anti-coplanar) (Dihedral angle of 180°)

Question 29

In a stereoselective E2 reaction

Answer 29

The substrate can produce two stereoisomeric products (Either cis or trans)

Question 30

In a stereospecific E2 reaction

Answer 30

The substrate is stereoisomeric & the stereochemical product is dependent on which stereoisomeric is used

Question 31

An E2 reaction occurs by a ____________ conformation

Answer 31

Anti-periplanar

Question 32

For an E2 reaction to occur with a cyclohexane chair conformation the leaving group must be on the _________ position to be anti-periplanar & react

Answer 32

Axial position

Question 33

E2 reaction can only happen with cylcohexanes (or any rings) when the leaving group & beta hydrogens are on \_\_\_\_\_\_\_\_\_\_\_

Answer 33

Opposite planes (If the LG is on a wedge then the Beta hydrogens has to be on a dash to form the anti-periplanar to react)

Question 34

The _______ mechanism is the stepwise reaction

Answer 34

E1

Question 35

What is the rate law of an E1 reaction?

Answer 35

R = k[substrate] (unimolecular) (The rate determing step is the loss of LG)

Question 36

\_\_\_\_\_\_\_\_\_\_ halides favor the E1 mechanism & primary are least favored because the 1st step in E1 is the loss of LG which forms a carbocation & primary carbocation are least stable)

Answer 36

Tertiary halides

Question 37

In an E1 reaction if an alochol is the leaving group then a ______________ is needed to protonate it

Answer 37

Strong acid

Question 38

In an E1 reaction the regiochemistry can't be controlled by a base & the ______________ is usually produced

Answer 38

Zaitsev product

Question 39

E1 don't need a anti-periplanar conformation to react & favors the _________ product when stereoisomers are the products

Answer 39

Trans

Question 40

What are the two core steps of an E1 reaction?

Answer 40

1. Loss fo LG 2. Proton transfer

Question 41

What are the only 2 additional steps an E1 reaction can have?

Answer 41

1. Proton transfer before the 1st step (loss of LG) 2. Carbocation rearrangment in between the two core steps

Question 42

A proton transfer is needed at the beginning of an E1 reaction if an _________ is the leaving group & is needed to be protonated

Answer 42

Alcohol

Question 43

A carbocation rearrangement is needed in the middle of an E1 reaction if the carbocation can be \_\_\_\_\_\_\_\_\_\_\_\_

Answer 43

More stable

Question 44

An E2 reaction has ________ additional steps

Answer 44

Zero its only a concerted reaction where the proton transfer & loss of Lg occur aqt the same time

Question 45

Why doesn't E2 reaction have any additional steps?

Answer 45

It can't form a carbocation & it uses strong bases & an OH can't be protonated with a strong base

Question 46

\_\_\_\_\_\_\_\_\_\_\_ & ___________ reactions are always in competiton where sometimes one mechanims donminates & forms one product & other times both dominate & form multiple products

Answer 46

Substitution & Elimination reaction

Question 47

How do you determine which product is major & minor?

Answer 47

1. Determine the function of the reagent 2. Analyze the substrate & determine the expected mechanisms 3. Consider any relevant regiochemical & stereochemcial requirements

Question 48

A substitution reaction occurs when the reagent acts as a ___________ & an elimination reaction occurs when the reagent acts as a \_\_\_\_\_\_\_\_\_

Answer 48

Nucleophile, Base

Question 49

Nucleophilicity

Answer 49

A kinetic phemomeon & refers to the rate of the reaction (refers to the rate at which a nucleophile attack an electorphile)

Question 50

Basicity

Answer 50

A thermodynamic phenomeon & refers to the position of equilibrium

Question 51

Factors that contribute to nucleophilicity

Answer 51

1. Charge on an atom 2. Polaraziability (More important than charge)

Question 52

Polarziabaility is directly portportional to the \_\_\_\_\_\_\_\_\_

Answer 52

Atomic mass

Question 53

In a proton equilbium it will favor the \_\_\_\_\_\_\_\_\_

Answer 53

The weaker base

Question 54

Reagents that are only strong nucleophiles indicates what type of reaction?

Answer 54

Substitution reaction

Question 55

What are the reagents that are only strong nucleophiles?

Answer 55

1. Cl^- 5. RS^- 2. Br^- 6. H₂S 3. I^- 7. RSH 4. HS^-

Question 56

Reagents that act only as strong bases indicate what type of reaction?

Answer 56

Elimination reaction

Question 57

What are the reagents that function only as strong bases?

Answer 57

1. H^- 2. DBN 3. DBU

Question 58

Reagents that function as both strong nucleophile & strong bases indicates what type of reaction?

Answer 58

SN2 & E2

Question 59

What are the reagents that are both strong bases & nucleophiles?

Answer 59

1. HO^- 2. MeO^- 3. EtO 4. RO^-

Question 60

Reagents that are both weak nucleophile & bases indicate what type of reaction?

Answer 60

SN1 & E1

Question 61

What reagents function as both weak nucleophile & base?

Answer 61

1. H₂O 2. MeOH 3. EtOH 4. ROH

Question 62

Protic solvents favor what type of reactions?

Answer 62

SN1 & E1

Question 63

Aprotic solvents favor what type of reaction?

Answer 63

SN2 & E2

Question 64

When a ______________ base is present (ex. t-ButOK) then the major product is the hofman product

Answer 64

Sterically Hindered (Bulky bases)

Question 65

\_\_\_\_\_\_\_\_\_\_\_\_\_\_ are a result of a sterically base being used

Answer 65

Less substituted

Question 66

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ refers to beta positions being identical or not (where if they are identical then one product will be formed & if they are non-identical then two or more products formed)

Answer 66

Regiochemistry

Question 67

When regiochemistry is not a factor (only have one beta position) then if there is two hydrogens on the beta position then _______________ comes into play where the trans conformation is the mjaor product

Answer 67

Stereoselectivity

Question 68

When regiochemistry & stereoselective isn't a factor because only one beta position & there is only one hydrogen present then _______________ comes into play where have to make a newman projection so that the leaving group & beta hydrogen are anti-perilinear & then have to draw the newman projection that make them anti-perilinear

Answer 68

Stererospecific