Quiz 5

Question 1

Nucleophilicty

Answer 1

the strenght of a nucleophile, how fast does the nucleophile attack an electrophile

Question 2

Name the four factors that affect nucleophilicty

Answer 2

1. size
2. charge
3. solvent
4. polarizibility

Question 3

How does size affect nucleophilicity?

Answer 3

a smaller atom is favored

excpet in polar protic solvents

Question 4

How does charge affect nucleophilicty?

Answer 4

a nucleophile with a charge will be stronger

Question 5

How does polarizibility affect nucleophilicty?

Answer 5

it determines how well the nucleophile can unevelnly dsitrubite a charge

Question 6

How does a solvent affect nucleophilicity?

Answer 6

it can slow down or speed up the rxn by creating a solvent shell around the nucleophile or not

Question 7

Polar protic solvent

Answer 7

has hydrogen bonding, bad for SN2 rxns bc it creates a solvent shell

but favored for SN1

Question 8

Polar aprotic solvent

Answer 8

does not have hydrogen bonding, good for SN2 reactions because it doesnt create a solvent shell

Question 9

Inversion of configuration

R–S or S–R

Answer 9

when a reactant starts with one configuration and the products end with the other configuration

happens bc back side attack

Question 10

Backside attack

Answer 10

nucleophile attatches on opposite side of leaving grp

affects how you draw the mechanistic arrow

Question 11

Beta elimination

E2 rxn

Answer 11

when an alykl halide is treated with a strong base and a pi bond is formed
- proton transfer + loss of a leaving group

Question 12

What are the products of a beta elimination?

Answer 12

con A of base + solo halogen + Alkene

Question 13

Is an E2 reaction bimolecular and concerted or bimolecular and stepwise?

Answer 13

An E2 reaction is bimolecular and concerted
- relying on the substrated and the base for its rate

Question 14

There must be a — on the beta carbons or an — reaction cant happen

Answer 14

Hydrogen, beta elimination/E2

Question 15

In an E2 rxn the alkene must form between the — and —

Answer 15

alpha C and Beta C

Question 16

How can a base affect the E2 rxn?

Answer 16

It can speed it up or slow it down depending on its strenght
- the stronger the base is the faster it can deprotonate the molecule

Question 17

What is the key difference between an E2 and SN2 rxn?

Answer 17

You want a more sterically hindered product, because they are more stable and a sterically hindered substrate so the H are accesible for the base

Question 18

True or false?

A cis alkene is more stable than a trans alkene bc there is resonance

Answer 18

false, a trans alkene reduces interaction between substituents

Question 19

put 1,2,3,and 4 substitued alkenes in order of increasing stability

Answer 19

monosub<disub<trisub<tetrasubstitued

Question 20

Regioselectivity

Answer 20

when there is a major/minor product produced and one is favored over the other, the region where the reaction takes place

Question 21

True or false?

The more highly substitued the base is the more likely the Zatisev product will be favored

Answer 21

False, the more subsituted the base is the more likely the hoffman product will be favored (the less substitued alkene)

Question 22

Zatisev product

Answer 22

more substitued alkene

Question 23

Hoffman product

Answer 23

less substitued alkene

Question 24

Stereospecific

Answer 24

One beta H, produces one stereoisomer (most stable one)

SN2 and E2 under right conditions

Question 25

Stereoselective

Answer 25

2+ beta H, will produce a major and minor product in unequal amounts | E2 rxns

Question 26

Anti coplanar/anti periplanar

Answer 26

staggard conformation where Beta H and leaving group on opposite planes of each other | lower E makes this the favorable conformation

Question 27

Periplanar/syn-planar

Answer 27

eclipsed conformation where Beta H and leaving group are on the same direction | very high E transistion state, not favorable for a E2 reaction

Question 28

If a molecule is syn-planar/periplanar what should you do?

Answer 28

rotate the bonds so the molecules are anti planar

Question 29

If an E2 reaction is happening with a substitued cyclohexane what has to be true of the leaving group and beta H?

Answer 29

1. leaving group has to be axial 2. the leaving group and beta H have to be anti coplanar/antiperi planar to each other (just like in non cycloalkanes)

Question 30

How do unimolecular reactions differ from the biomolecular substituion and elimination reactions?

Answer 30

1. these reactions occur stepwise: at least two transition states and one intermediate 2. rate depends only on the substrate and not the solvent 3. Both SN1 and E1 prefer a hindered substrate

Question 31

what is the first step of a unimolecular substitution and elimination reaction and what determines what the next mechanistic step is?

Answer 31

first step: Loss of a leaving group the solvent determines if a nucleophilic attack or a proton transfer will follow

Question 32

# True or false? A unimolecular reaction will produce both SN1 and E1 products

Answer 32

True! one will just be featured more depending on the solvent

Question 33

Adding --- to a unimolecular reaction will increase the likelihood of a Elimation reaction?

Answer 33

Heat will increase the probability of an elimination reaction

Question 34

Unimolecular reaction favor a --- substrate

Answer 34

hindered

Question 35

# True or false? a primary vinylic and allylic carbocation can never form

Answer 35

false, an allylic primary carbocation can form because of resonance. aryl and vinyllic cannot form

Question 36

What kind of solvent is favored for a unimolecular reaction?

Answer 36

Polar protic, it can stabilize the partial charges (carbocations) that form during the reaction

Question 37

If your product has a charge at the end of the reaction what should be done?

Answer 37

a proton transfer, a charged product is higly unlikely because it would be unstable

Question 38

# True or false? Just like SN2 an SN1 reaction will always produce inversion of configuration

Answer 38

false, an SN1 reaction will produce both retention and inversion products

Question 39

In unimolecular reactions will the hoffman or zaitsev product be favored?

Answer 39

Zaitsev, more substiuted and more stable | the E isomer will also likely be favored

Question 40

What are the four catagories of reagant?

Answer 40

1. Strong nucleophile, acts only as a nucleophile 2. strong base, acts only as a base 3. strong nucleophile, strong base 4. weak nucleophile, weak base

Question 41

What kind of reaction does a strong nucleophile that acts only as a nucleophile promote?

Answer 41

this will promote a SN2 reaction

Question 42

Examples of strong nucleophiles that act only as nucleophiles

Answer 42

solo halogens: I-, Br-, Cl- HS-

Question 43

what kind of reaction does a strong base that only acts as a base promote?

Answer 43

likely will promote an E2 reaction

Question 44

example of strong bases that act only as bases

Answer 44

DBU, DBN, tert-butoxide, strong bulky bases

Question 45

What kind of reaction do strong nucleophile/strong base promote?

Answer 45

Bimolecular reactions

Question 46

examples of strong nucleophile/ strong base

Answer 46

charged O- or N-, MeO-, EtO-, -OH

Question 47

What kind of reactions will a weak nucleophile/ weak base promote?

Answer 47

unimolecular reactions

Question 48

examples of weak bases/ weak nucleophiles

Answer 48

neutral oxygens, Water, Alcohols MeOH, Et,OH, H2O

Question 49

# True or false? A heavily subsiuted substrate will indicate any reaction that is not SN2

Answer 49

True, Sn2 is the only reaction that does not favor a hinderd substrate

Question 50

Will the zaitsev or hoffman product be favored in an E1 reaction?

Answer 50

In an E1 reaction zaitsev is always favored