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Organic Chem > Unit 3 > Flashcards

Unit 3 Flashcards

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1
Q

syn addition rxs

A

both atoms add to the same side of the ring to form a cis product

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2
Q

if a syn reaction occurs with a compound that is chiral, what is the product

A

the product formed from the above and below reactions will form, and they may be diasteromers or enantiomers

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3
Q

concerted mechanism

A

when all of the bond breaking and forming occurs without the formation of an intermediate

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4
Q

anti addition

A

groups are added to the opposite side of ring to form a trans product

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5
Q

what kind of mechanisms are used in syn reactions

A

concerted

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6
Q

what kind of mechanisms are used in anti reactions

A

step wise

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7
Q

step wise mechanism

A

the addition occurs in a step wise manner with the formation of an intermediate

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8
Q

what a makes halogens effective electrophiles

A

they are nonpolar but highly polarizable

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9
Q

what types of atoms make the best leaving groups

A

stable ions

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10
Q

what types of reagents and solvents are needed for a halogenation reaction

A

the reagent must be Cl2 or Br2

the solvent must be a nonnucleophile

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11
Q

why must the solvent in a halogenation reation be a non-nucleophile

A

because a nucleophillic solvent would compete with the reagents and react with Cl or Br

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12
Q

what type of mechanism is halogenaton

A

2 step mechanism

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13
Q

what are the two step to a halogenation reaction

A

1) the electrons of the alkene pi bond flow into the first halogen, pushing the H atoms to one side and creating a partial carbocation and an halide ion
2) the free floating halide attaches to the partial carbocation on the opposite side of the ring

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14
Q

why doesn’t the halogen reaction not fully form a carbocation

A

because as the carbon becomes electron deficient the electrons from the halogen form a sigma bond

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15
Q

bronsted acid

A

a proton donor (H3O)

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16
Q

bronsted base

A

a proton acceptor (OH)

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17
Q

neutral acids form

A

negative CB

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18
Q

positive acids form

A

neutral CB

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19
Q

negative bases form

A

neutral CA

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20
Q

neutral bases from

A

positive CAs

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21
Q

what type of reaction mechanism is used in an acid base reaction

A

concerted

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22
Q

how is the strength of an acid determined

A

how many other molecules will a molecule force a proton on to

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23
Q

how does pKa relate to the strength of an acid

A

a lower pKa means a stronger acid

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24
Q

how strong will the conjugate base of a weak acid be? why?

A

it will be strong, because the acid will not be likely to give up protons but will easily accept them

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25
Q

how strong will the conjugate base of a strong acid be

A

it will be weak, because the acid will be very liked to give up protons and not easily accept them

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26
Q

if given an acid reaction, what is used to determine what direction the reaction will go? why?

A

the reaction will favor the stronger acid, because a stronger acid will create a weaker base with a strong negative charge

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27
Q

what are the 4 factors that influence the stability of a negative charge (ARIO)

A

1) type of atom
2) resonance
3) induction
4) orbitals

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28
Q

how does the type of atom influence stability of a negative charge

A

larger, more electronegive atoms are better at stabilizing a negative charge

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29
Q

what is characteristic of an atom is more important in stabilizing negative change, size or electronegativity (example)

A

size (S stabilizes better than oxygen)

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30
Q

how does resonance stabilize negative charge

A

by spreading the charge over several atoms

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31
Q

induction

A

the attraction of negative charges to more electronegative atomes

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32
Q

how does induction stabilize negative charge

A

it spreads charge out like resonance

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33
Q

what are two factors influencing induction (examples)

A

1) electronegativity (F is more inductive than Cl)

2) distance (induction can only cross 3 bonds)how a

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34
Q

how do orbitals influence the stability of a negative charge

A

sp orbitals pull electrons closer to the nucleus and stabilze the charge

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35
Q

hoow are oribitals ranking according to their ability to stabilize negative charge

A

sp > sp2 > sp3

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36
Q

counter ion

A

spectator ion

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37
Q

if LiH is in a problem, what is happening

A

the LiH will dissociate into Li+ and H-, and the Li will find another atom to attach to

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38
Q

what is the leveling effect

A

the strongest base in the reaction will always take the most acidic proton from the strongest acid

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39
Q

T/F a conjugate acid stronger than the solvent in the reaction can’t exist

A

true, any acid stronger than the conjugate acid of your solvent will donate protons to the solvent

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40
Q

in a reaction where the desired product is a base, what is important to remember

A

the solvent can’t form a more basic molecule than the desired base because the product will take protons from the solvent and not form

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41
Q

in a reaction where the desired product is an acid, what is important to remem ber

A

the solvent can’t form a stronger conjugate acid than the product or the product will give its protons to the solvent and not form

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42
Q

lewis acids

A

electron acceptor

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43
Q

lewis bases

A

electron donor

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44
Q

what are three examples of lewis acids that arent bronsted acids

A

AlR3, BrR3, CR3+

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45
Q

what do all the common lewis acids that are bronsted acids have in common

A

Al and Br are stable with three electrons

carbocation is an intermediate

46
Q

what are the 6 steps for naming an alkene

A

1) the parent chain must include both C=C carbons
2) identify and name all the substituents
3) number the parent chain so the alkene has the lowest number
4) number the substituents
5) list the number substituents in alphabetical order
6) end the parent chain with -ene

47
Q

what happens when the longest chain of an alkene doesn;’t include the whole alkene

A

the shorter chain that does include the alkene is used

48
Q

what are dienes and how are they named

A

molecules with two alkenes

-adiene

49
Q

T/F the parent chain of a diene includes both alkene bonds

A

true

50
Q

can the bonds on an alkene rotate?

A

no

51
Q

how many isomers are possible in cyclic alkenes with less than 8 carbons

A

1, only cis alkenes are possible with less than 8 carbons

52
Q

T/F if one of the carbons of an alkene has identical groups there is no stereoisomer of that alkene

A

true

53
Q

what is the E/Z designation used for

A

it takes the place of cis and trans when there are different groups on each carbon

54
Q

what does Z stand for

A

a cis configuration in an alkene with four different groups

55
Q

what does E stand for

A

a trans configuration in an alkene with four different groups

56
Q

when are cis and trans used to designate alkenes

A

when the two carbons have identical groups

57
Q

nucleophiles

A

atoms or molecules that are attracted to positive charges

58
Q

electrophiles

A

atoms or molecules that are attracted to negative charges

59
Q

T/F the conjugate bases of most acids function as electrophiles

A

false, they function as nucleophiles

60
Q

T/F nucleophiles/electrophiles will never react with molecules of the same type

A

true

61
Q

what is needed for a carbon atom to produce a nucleophile

A

a pi bond or a nonbonding pair

62
Q

what are two functions of the leaving group

A
  • it removes electron density from a carbon to make it electrophilic
  • it is able to stabilize a negative charge after it is expelled
63
Q

what is needed for oxygen to be nucleophilic

A

a pi bond, a nonbonding pair, or a OH bond

64
Q

can a neutral oxygen be nucleophilic

A

yes

65
Q

what is more nucleophilic, an anion or a neutral atom

A

the anion (S-, O-)

66
Q

what is needed for sulfur to be nucleophillic

A

a nonbonding pair, a pi bond, or an SH bond

67
Q

what are 9 common electrophiles

A

1) carbocations
2) ketones
3) aldehydes
4) esters
5) amides
6) halogens
7) expoxides
8) alkyl halides
9) acids)

68
Q

T/F electrophiles will interact with other electrophiles

A

false

69
Q

why are halogens considered be electrophiles

A

because they can flucuate in electron arrangement rapidly and attract electrons from a nucleophile

70
Q

when deciding a nucleophile and electrophile will react what are two considerations

A

1) weak bonds break easier than strong bonds

2) a strong base will displace a weak base

71
Q

why can the electrons from pi bonds flow into electrophiles more easily than those from sigma bonds

A

because of the orientation of the p orbital the electrons are not found between the nuclei

72
Q

why can alkenes act as bases and nucleophiles

A

because the pi bond of an alkene acts like a less active nonbonding pair

73
Q

what type of reaction is common with alkenes

A

addition reactions

74
Q

what are three types of addition reactions

A

1) cation forming reactions
2) syn-addition reactions
3) anti-addition reactions

75
Q

three types of addition reactions that require an acid

A

1) hydrohalogenation
2) hydration
3) hydroalkoxyation

76
Q

what is the process of hydrohalogenation

A

a binary acid added to an alkene forms an alkyl halide as one C gets an H and one C gets an X

77
Q

racemic mixture

A

when two possible stereoisomers are present in equal amounts

78
Q

what is the process of hydration

A

H2O added to an alkene produces alcohol

79
Q

markinovs rule

A

in an addition reaction the carbon with the most hydrogens will get the hydrogen

80
Q

why dont alkenes react with H2O

A

they are both nucleophiles

81
Q

what will make an alkene react with water

A

any amount of an acid to form H3O and act as a catalyst

82
Q

what is a solvent typically used in hydration reactions

A

a polar organic solvent that will produce a homogenous mixture with water (dimethylsulfoxide)

83
Q

what happens in a regioselective reaction

A

one of the possible products is formed more often than the others

84
Q

what is the effect of substitution on alkene reactions

A

the more carbons an alkene has attached the faster it will react

85
Q

T/F the halogen in a hydrohalogenation reaction will always end up on one of the alkene carbons

A

false

86
Q

what are two types of carbocation rearrangement

A
  • hydride shift

- methyl shift

87
Q

hydride shift

A

the movement of an H to another adjacent carbon

88
Q

methyl shift

A

the movement of a CH3 group to an adjacent carbon

89
Q

what determines if a methyl or hydride shift can happen

A
  • they will only happen to gain more resonance stabilization

- they will only shift if the recipient of the positive charge is the atom with the most C-C bonds

90
Q

can a CH2+ ion carbocation do a hydride or methyl shift with a CC2H carbon?

A

yes, because the CC2H carbon is more able to hold positive charge

91
Q

how is deutritum used in determining reaction mechanisms

A

deutritium is used instead of regular hydrogen

92
Q

deuterium

A

a hydrogen atom with one proton and one neutron

93
Q

what is the stepwise mechanism for a hydration reaction

A

1) H3O donates a proton to one of the alkene carbons
2) H2O forms oxonium with the carbocation formed
3) the positive oxonium donates an electron H2O to reform H3O
4) the result is an alcohol

94
Q

what makes carbocation rearrangement possible in a reaction

A

the formation of a carbocation

95
Q

why are carbocation rearrangements problematic for organic reactions with a specific end result

A

they are very fast and unstoppable, so H-X reactions are only useful when rearragements won’t occur

96
Q

what is meant by the “least” substituted carbon

A

the least substituted carbon is the carbon with the fewest C-C bonds

97
Q

why do the H goto the carbon with the most H’s in markinovs rule

A

because the carbon with the most H’s would form the less stable carbocation if it didn’t get H

98
Q

what will be the result of a hydrogenation reaction

A

the syn additition of two hydrogens

99
Q

when will any syn addition reaction produce enantiomers

A

when the molecule added onto is chiral

100
Q

what is syn dihydroxylation?

what are the catalysts used

A

the syn addition of two OH groups to an alkene

OsO4, KMno4

101
Q

what is the result of dihyrdroxylation

A

the syn addition of two OH groups producing a vicinal diol

102
Q

vicinal diol

A

a molecule with an OH group on adjacent carbons

103
Q

what are the two steps of a dihydroxylation reaction

A

1) the oxygens of OsO4 or KMnO4 are added simultaneously to the alkene carbons
2) the 2nd reactant breaks the rest of the molecule away to leave only the OHs

104
Q

what are the two steps of a dihydroxylation reaction

A

1) the oxygens of OsO4 or KMnO4 are added simultaneously to the alkene carbons
2) the 2nd reactant breaks the rest of the molecule away to leave only the OHs

105
Q

What is hydroboration/Oxidation

A

the process by which an OH group is added to the most substituted carbon (with the most C bonds) and an H to the least substituted carbon

106
Q

why is hydroboration special

A

because it is the only reaction we learn about that added hydrogens in an anti-markovnikov fashion

107
Q

what is the process of hydroboration

A

1) BH3 attaches it BH2 to the carbon with the most hydrogens, the H attaches to the C with the least hydrogens
2) BH2 is cleaved off by a second reactant to leave an OH behind

108
Q

what are there reactants in hydroboration/oxidation

A
  • Borane (BH3)
  • KOH
  • H2O2
109
Q

what is THF

A

an additive in a hydroboration reaction that helps stabilize borane

110
Q

when would the H’s on a CH2 not be equivalent on NMR

A

when the CH2 is adjacent to a chirality center

111
Q

what is oxymercuriation

what are the reagents used

A
  • the anti addition of an OH and H without carbocation rearragement through a Hg cyclic intermediate
  • Hg(OAc)2, NaBH4
112
Q

what will a reaction with MCPBA produce

A

an epoxide from an alkene

Organic Chem (8 decks)

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