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Organic Chemistry - MCAT > Class Three > Flashcards

Class Three Flashcards

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1
Q

is there a net change in the number of pi or sigma bonds in nucleophilic sub.

A

no. one sigma bond is broken & another is formed

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2
Q

SN2 reaction

A

bond forming and bond breaking occurs simultaneously

involves two molecules

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3
Q

product of an SN2 reaction

A

inverted product (at the carbon being attacked by the nucleophile)

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4
Q

what type of attack occurs in SN2

A

backside attack

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5
Q

SN2 rate of reaction

A

bimolecular - depends on the concentrations of the nucleophile & electrophile

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6
Q

bulkiness - SN2

A

less substituted substrates react faster than more substituted ones in SN2

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7
Q

why are protic solvents avoided for SN2

A

hydrogen bonding solvents → strongly solvate the nucleophile & hinders backside attack

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8
Q

what happens in an SN1 reaction

A

a carbocation forms

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9
Q

order of carbocation stability

A

tertiary carbocations are more stable than primary ones

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10
Q

SN1 reactions occur in..

A

2 steps

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11
Q

steps of SN1 reactions

A

leaving groups dissociates

racemization occurs: nucleophile attacks equally on either side of the carbocation

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12
Q

rate limiting step - SN1

A

leaving group dissociating

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13
Q

SN1 reaction

A

unimolecular - only depend on electrophile concentration

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14
Q

how to speed up an SN1 reaction

A

more substituted carbocation = more stable intermediate = speed up

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15
Q

why are protic solvents used for SN1

A

protic solvents = alcohol or water

stabilizes the forming carbocation & acts like the nucleophile in a solvolysis reaction

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16
Q

water as solvent SN1

A

produces an alchohol product

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17
Q

alcoholic solvent SN1

A

produces an ether product

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18
Q

oxidation of an alcohol =

A

formation of a carbonyl

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19
Q

what is a carbonyl

A

carbon double bonded to oxygen

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20
Q

primary alcohols are oxidized to..

A

aldehydes

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21
Q

secondary alcohols are oxidized to..

A

ketones

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22
Q

tertiary alcohols are oxidized into..

A

no reaction

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23
Q

why are the alpha protons acidic

A

the electrons left behind upon deprotonation can delocalize into the pi system

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24
Q

enolate ions are..

A

negatively charged and nucleophilic

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25
Q

when is a proton acidic

A

when it has a very high positive charge

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26
Q

what is an enol

A

alkene + alcohol

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27
Q

how is a ketone converted to an enol

A

deprotonation of an alpha-carbon and of the carboxyl oxygen

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28
Q

what are tautomers

A

two molecules - interconvertible constitutional isomers in equilibrium

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29
Q

characteristics of a strong reducing agent

A

easily loses electrons

have lots of hydrogens attached to other elements with low electronegativity

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30
Q

Grignard reagent

A

alkyl halide + magnesium

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31
Q

carbonyl + Grignard reagent →

A

alcohol

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32
Q

how to protect alcohols

A

transform them into mesylates & tosylates

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33
Q

in SN1 reactions, ___ alcohols are favoured

A

tertiary

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34
Q

in SN2 reactions, ___ alcohols are favoured

A

primary

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35
Q

why do alcohols get protected

A

to prevent them as acting as an acid or nucleophile

36
Q

what is a mesyl

A

CH3=SO3-

protection of alcohol

37
Q

what is a tosyl

A

CH3C6H4-SO3-

protection of alcohol

38
Q

why is a base required when protecting alcohols

A

neutralizes the HCl and pull it out of solution as a salt

39
Q

mesylate and tosylate are ___ leaving groups

A

good

hydroxyl is bad and can be converted into these

40
Q

difference between acetals and hemiacetals

A

acetals have 2 OR groups and hemiacetals have an OR and a OH group

41
Q

when do acetals form

A

when aldehydes/ketones react with alcohol in the presence of acid

42
Q

how to turn hemiacetal → acetal

A

remove a molecule of water

43
Q

how is a cyanohydrin formed

A

aldehydes/ketones reacting with HCN → cyanohydrin

44
Q

amine general structure

A

R-NH2

45
Q

alkyl vs aryl amines

A

alkyl: N is bonded to an sp3 hybridized carbon
aryl: N is bonded to an sp2 hybridized carbon of an aromatic ring

46
Q

primary/sec/tert/quart amines

A

of R groups on the N

47
Q

molecular geometry of an alkyl amine is..

A

pyramidal

48
Q

amines behave as..

A

BL bases or nucleophiles (bc of the lone pair of electrons)

49
Q

a weak base is..

A

a good leaving group

50
Q

keto and enol tautomers are _____ isomers

A

structural

51
Q

which is more stable - keto or enol

A

keto

52
Q

how to make a reaction with a weak nucleophile

A

by making the electrophile more electron deficient (add acid)

53
Q

what is a hydride reaction

A

either fewer bonds to O or more bonds to H

54
Q

Grignard reagents are ___ nucleophiles

A

strong

55
Q

what is a common trait of hemiacetals and acetals

A

one carbon bonded to two Os

56
Q

how many alcohols needed to make an acetal

A

2

57
Q

can you reverse from an acetal to the original ketone/aldehyde

A

yes

58
Q

alcohol + aldehyde/ketone =

A

acetal

59
Q

aldehyde/ketone + primary amine =

A

imine

60
Q

aldehyde/ketone + secondary amine =

A

enamine

61
Q

what is an aldol condensation

A

enolate anion of one carbonyl + carbonyl group of another carbonyl compound

62
Q

aldol condensations requires a ____ base

A

strong

63
Q

kinetic vs thermodynamic control

A

thermodynamic: will remove protons from the more sterically crowed carbon
kinetic: will remove protons from the less crowded carbon (not enough energy)

64
Q

what is a β-hydroxy carbonyl

A

hydroxyl group bonded to the beta carbon of an aldehyde/ketone

65
Q

what is a retro-aldol reaction

A

β-hydroxy carbonyl decomposes into a aldehyde/ketone + a carbonyl compound

66
Q

why can carboxylic acids form strong H bonds

A

contains an H bond donor (acidic proton) and an H bond acceptor (e on O)

67
Q

carboxylic acids can be recused into..

A

primary alcohols

68
Q

CAs can be reduced with ____ but not ____

A

LiAlH4 but not NaBH4

69
Q

why are CAs that have carbonyl groups beta to the carboxylate unstable

A

they are subject to decarboxylation (loss of CO2)

70
Q

carboxylic acid derivatives (4)

A

acid halide, acid anhydride, ester and amide

71
Q

characteristic of an elimination reaction

A

2 sigma bonds break and 1 pi bond forms (opposite from addition reaction)

72
Q

esterification

A

carboxylic acid + alcohol in the presence of acid (catalyst)

73
Q

acid & base catalyzed ester hydrolysis

A

both involve nucleophilic addition and elimination steps

same products, different mechanisms

74
Q

saponification is an example of..

A

base-mediated ester hydrolysis

75
Q

saponification reaction

A

tricylglyceride (in the presence of base) → glycerol + fatty acids

76
Q

how are acid halides made

A

carboxylic acid + PX3 (some halogen)

77
Q

how are acid anhydrides made

A

condensation of 2 CAs with the loss of water

OR

CA + acid halide

78
Q

how are esters made

A

CA + alcohol

79
Q

how are amides made

A

from an acid halide, anhydride or ester + amine

can NOT be made from CA directly (amides are very basic)

80
Q

reactivity of acid derivatives in nucleophilic addition/elimination reactions decreases with..

A

inching basicity of the leaving group

81
Q

order of reactivity in nucleophilic addition/elimination reactions

A

acid chlorides > acid anhydrides > esters > amides

82
Q

aldol condensation products

A

beta-hydroxyl carbonyl OR alpha-beta unsaturated carbonyl

83
Q

aldol reaction starting

A

nucleophilic enolate reacts with aldehyde/ketone

84
Q

activate our electrophile =

A

protonation

85
Q

activate our nucleophile =

A

deprotonation

Organic Chemistry - MCAT (4 decks)

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