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Ochem > chapter 9 > Flashcards

chapter 9 Flashcards

0
Q

in an sn2 mechanism when does the bond breaking and forming occur?

A

the occur at the same time

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1
Q

what is the difference between sn1 and SN2 reactions ?

A

the timing of the bonds breaking and forming

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2
Q

the sn2 is an example of a unimolecular or bimolecular mechanism ?

A

bimolecular

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3
Q

what is involved in the rate determining step of the sn2 mechanism?

A

the haloalkene and the nucleophile are both involved in the rate determining step

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4
Q

does the sn2 mechanism happen via the from or back side?

A

backside attack for sn2

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5
Q

how many steps are involved in sn2

A

just one step!

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6
Q

describe the sn1 mechanism , when are the bonds broken and formed

A

bond breaking is completed before any bonds are formed with the nucleophile

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7
Q

is sn1 unimoleular or bimolecular

A

sn1 is unimolecular

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8
Q

what is involeved in the rate determining step in an sn1 mechanism

A

the haloalkane is involved in the rate determining step in an sn1 mechanism

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9
Q

are there intermediates in SN2 reactions ?

A

no

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10
Q

are there intermeditates in SN1 reactions?

A

yes , a carbocation intermediate is formed

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11
Q

is the nucleophile involved in the kinetics of an SN1 reaction

A

no, just the haloalkene is involved in the rate mechanism

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12
Q

describe the 2 things that are involved in an sn2 mechanism

A

the substrate and the nuclephile

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13
Q

describe the stereochemistry of the sn1 mechanism

A

a racemic mixture is formed

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14
Q

describe the stereochemistry of an sn2 mechanism

A

there is an inversion of configuration

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15
Q

the stability of carbocations in SN1 reactions are examples of what kind of factors

A

electronic factors

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16
Q

SN2 reactions are governed by what kind of factors

A

steric factros

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17
Q

in an SN1 reaction is a 3 or 1 more stable

A

a 3 is more stable

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18
Q

an allylic or benzellic carbocation is more stable in sn1 or SN2 reactions

A

sn1

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19
Q

describe what an allylic carbon looks like

A

it has a double bond next to the carbocation

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20
Q

what makes a benzylic carbocation so stable

A

its ability to make resonance structures

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21
Q

in SN2 reactions are we more likely to see 1 or 3 carbocations

A

1 , because we dont want steric hinderance in SN2 reactions

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22
Q

describe what beta branching is

A

these are branches that are coming off of the central carbon

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23
Q

the less beta branches that something has … the …the reaction

A

the less beta branches the faster the reaction

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24
Q

what is the charge like on sn1 and SN2 reaction leaving groups

A

there is a partial negative charge on the leaving group in both sn1 and SN2 reactions

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25
Q

what makes the best kind of leaving group?

A

the best leaving groups are those that are weak bases (of strong acids )

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26
Q

weak bases are very stable or unstable antions?

A

weak bases make stable anions

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27
Q

which is a better leaving group i or f

A

i

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28
Q

which is a better leaving group br or cl

A

br

29
Q

what is the role of the solvent ?

A

it dissolves the reactant

30
Q

what are the 2 kinds of solvents

A

protic and aprotic

31
Q

what is something that we can use to determine is polar or non polar

A

we can use the dielectric constant to determine if something is polar or non polar

32
Q

if the dielectric constant of a solvent is 15 what kind of solvent is it

A

polar

33
Q

if the dielectric constant of a solvent is 5 or less what kind of solvent is it

A

non polar

34
Q

list the 3 kinds of POLAR PROTIC SOLVENTS YOU SHOULD KNOW

A

alcohols
water
formic acid

35
Q

dmso is what kind of solvent

A

aprotic

36
Q

acetone is what kind of solvent

A

aprotic

37
Q

what does the rate of an SN1 reaction depend on

A

the rate of an sn1 raction depends on the ability of a solvent to keep opposite charges separated and the ability to stabilize the charge

38
Q

what kind of solvents work best of SN1 reactions

A

polar protic solvents

39
Q

what kind of solvents work best for SN2 reactions

A

polar aprotic solvents

40
Q

what is nucleophilicity

A

it measures the rate at which it displaces a leaving group from a haloalkane

41
Q

nucleophiles are similar to what kind of bases

A

bronstead lawry bases

42
Q

why are nucleophiles and bronstead lawry bases similar

A

because they both deal with a lone pair of electrons

43
Q

what kind of base makes a good nucleophile

A

a strong base

44
Q

if something has a pka above 11 what kind of nucleophile is it

A

a pka above 11 means that it is a strong nucleophile

45
Q

if something has a pka below 11 what kind of nucleophile is it?

A

that means that it is a weak nucleophile

46
Q

in an aprotic solvent which is more nucleophilic f or i

A

f

47
Q

in a polar protic solvent which is more nucleophilic f or i

A

i

48
Q

which is more polarizible f or i

A

i is most polarizabile

49
Q

what do SN2 reactions have to worry about

A

steric hinderances

50
Q

in which ways are nucleophiles and bases similar

A

they both accept protons

51
Q

what is beta elimination

A

taking a proton away to break a bond to get a more stable molecule

52
Q

what kind of bases are needed for beta elimination

A

strong bases

53
Q

describe the zaitsev rule

A

the more substituted alkene is the dominant product, highlighter rule

54
Q

how do we do elimination ?

A

we look at the beta carbons and use beta hydrogens to determine where the double bond will be , also rememeber that the leaving group comes off !

55
Q

what are the 2 mechanisms of beta elimination

A

e1 and e2

56
Q

what is the difference between e1 and e2

A

the timing and breaking of the bonds

57
Q

describe the bond breaking etc of an e2 mechanism

A

the carbon and leaving group break to give the carbocaiton , before the reaction occurs . this means that it is a 2 step process

58
Q

is e1 bimolecular or unimolecular

A

it is unimolecular

59
Q

what is the rate determining step in an e1 mechanism

A

the haloalkane

60
Q

how many transition states are there in an e1 mechanism

A

there are 2 transition states

61
Q

t/f e1 and sn1 are always competing

A

true

62
Q

is the e2 mechanism a concerted process

A

yes

63
Q

what order are e1 reactions

A

they are 1st order

64
Q

what order are e2 reactions

A

they are 2nd order reactions

65
Q

is there rearrangement in e1 reactions

A

yes

66
Q

does e1 follow zaitsevs rule

A

yes

67
Q

if there is a fatty base what mechanism does it follow

A

e2

68
Q

if there is a fatty base is zaitsevs rule followed

A

no

69
Q

in which reaction must something be anti and coplanar

A

in e2 reactions

Ochem (12 decks)

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