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Organic Chem > Test 4 > Flashcards

Test 4 Flashcards

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1
Q

S* -> R*
reactant is 100% S
product is 100% R

A

considered an inversion

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2
Q

S* -> S*
reactant is 100% S
product is 100% S

A

considered retention of configuration

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3
Q

S* -> (S* + R*)
reactant is 100% S
product is 50/50%

A

considered racemization

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4
Q

substitute out the ___________

A

leaving group

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5
Q

substitute in the ___________

A

nucleophile

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6
Q

if the leaving group is to the left, the attack will come from the ______

A

right

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7
Q

what is the utility of an SN2 reaction

A

allows for a wide range of heteroatoms

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8
Q

what type of alkyl halide cannot do SN2 reactions

A

3rd degree

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9
Q

two reasons for opposite side attack

A
  1. columbic (charged) repulsions between nucleophile lone pair and the lone pair on the halogen
  2. steric bulk size of the halogen
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10
Q

best type of solvent for Sn2 reactions

A

polar aprotic

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11
Q

nonpolar solvents

A

no heteroatoms
just CH atoms

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12
Q

polar aprotic solvents

A

has heteroatoms like O, N, S (polar)
lack of O-H and N-H bonds (aprotic)

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13
Q

polar protic

A

has N-H or O-H bonds

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14
Q

why are polar protic solvents NOT good for Sn2 reactions

A

will have unwanted BL acid base reactions

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15
Q

why are nonpolar sovlents NOT good for Sn2 reactions

A

granular salt will not dissolve

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16
Q

racemization definition

A

optically active compounds (only one enantiomer) are converted into an equal mixture of enantiomers with zero optical activity

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17
Q

enantiomer

A

nonsuperimposable mirror images

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18
Q

diasteromers

A

nonsuperimposable, non mirror images

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19
Q

1st degree alkyl halide

A

ONE other carbon attached to the carbon attached to the halogen

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20
Q

2nd degree alkyl halide

A

TWO other carbon attached to the carbon attached to the halogen

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21
Q

3rd degree alkyl halide

A

THREE other carbon attached to the carbon attached to the halogen

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22
Q

X

A

halogen

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23
Q

geminal

A

coming off of the same carbon

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24
Q

vicinal

A

coming off of adjacent carbons

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25
Q

hydrogen bonds

A

hydrogen bound to oxygen, nitrogen, or flourine

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26
Q

higher dielectric constant =

A

more polar

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27
Q

dipole moment vectors show

A

magnitude and direction of polarity

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28
Q

steps for SN2 reactions

A

separate attacker (-) from (K, Li, Na)
draw opposite side attack
leaving group leaves, attacking group attaches on opposite side
stereochemical inversion

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29
Q

substrates in SN2 reactions are

A

sp3 hybridized

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30
Q

good leaving groups

A

weak bases
ex. halides

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31
Q

poor leaving groups

A

strong bases

32
Q

what degree of carbons can preform SN2 reactions

A

1 and 2 ONLY
3rd degree CANNOT

33
Q

impact of double bonds on SN2 reactions

A

leaving group directly attached to a double bond = NO REACTION

34
Q

nucleophilcity increases with

A

size

35
Q

polar protic vs polar aprotic

A

polar protic: proton (H) bound to an electronegative atom
polar aprotic: NO H bonds

36
Q

nucleophile charge

A

negative

37
Q

SN2 stands for

A

substitution
nucleophilic attack
2 reactants (rate determining step)

38
Q

best degree alkyl halide for SN2 reactions

A

first degree

39
Q

order of reactivity for SN2 reactions

A

methyl > 1st degree > 2nd degree > 3rd degree

40
Q

aromatic compounds and SN2 reactions

A

DO NOT participate because of double bonds
carbon with halide attached must be at least one carbon removed from the ring for SN2 to occur

41
Q

how to determine best compound for SN2 reaction if all are same degree carbons

A

look at adjacent carbons (1st, 2nd, 3rd, 4th degree?)

42
Q

if substrates are the same, how do you determine which reaction will occur faster?

A

look at nucleophiles
stronger nucleophile (-) = raster reaction

43
Q

periodic trends in regards to nucleophiles

A

moving from right to left, basicity increases and therefore nucleophile strength increases

moving top to bottom, atom size and electronegativity increases, therefore nucleophile strength increases due to increased polarity of atom

44
Q

can SN2 reaction occur on sp2 molecules

A

no

45
Q

rate equation for SN2

A

rate = k [Rx] [Nu]

46
Q

invert

A

in all cases of a halogen

47
Q

if less than 0.5 D

A

NON-polar

48
Q

nucleophilic attackers

A

negative atoms

49
Q

alkyl halide

A

RX

50
Q

leaving group

A

X (F, Cl, Br, I)

51
Q

if leaving group is on a w/h

A

nucleophile will end up on the inverted w/h

52
Q

push only happen with

A

in plane

53
Q

determining which RX will have faster SN2 reaction

A

degree of alkyl halide
degree of electronegativity of leaving group

53
Q

as electronegativity increases

A

basicity decreases

54
Q

as steric bulk increases

A

basicity increases

55
Q

1 carbon

A

common: meth
IUPAC: form

56
Q

2 carbon

A

common: eth
IUPAC: acet

57
Q

3 carbon

A

common: prop
IUPAC: propion

58
Q

4 carbon

A

common: but
IUPAC: butyr

59
Q

5 carbon

A

common: pent
IUPAC: valer

60
Q

6 carbon

A

common: hex
IUPAC: capro

61
Q

allyl

A

3 carbons
x- - =

62
Q

vinyl

A

2 carbons
X - =

63
Q

benzyl

A

7 carbons
6 carbon ring - -x

64
Q

phenyl

A

6 carbons
6 carbon ring - x

65
Q

amide

A

NH2

66
Q

cyanide

A

-CN

67
Q

acetylide

A

-C tripple bond C-

68
Q

greater orbital size mismatch =

A

weaker bond

69
Q

weaker bond =

A

faster leaving group

70
Q

non resonance nucleophiles

A

negative charge only on 1 atom
faster than resonance nucelophiles

71
Q

free radicles

A

one unpaired electron

72
Q

stability for carbocations

A

3 > 2 > 1 > methyl

73
Q

stability for carboanions

A

methyl > 1 > 2 > 3

74
Q

stability for radicals

A

3 > 2 > 1 > methyl

75
Q

strong nucleophiles are structurally

A

NOT BULKY

76
Q

why are polar aprotic solvents best for SN2 reactions

A

no unwanted BL acid base reactions
both organic and ionic nucleophiles will dissolve

Organic Chem (6 decks)

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