Organic Chemistry Flashcards

1
Q

Factors that affect the melting points of organic compounds

A
  • molar mass
  • branched + straight chain isomers
  • functional groups
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2
Q

How does the molar mass affect the melting point of an organic compound

A

the greater the molar mass, the greater the strength of LDFs, which increases the melting point

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3
Q

How does the branching or straight chain isomers affect the melting point of an organic compound

A

the branches reduces the surface area of contact between molecules, which decreases the strengths of LDFs and thus decreases the melting point

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4
Q

How does the functional group affect the melting point of an organic compound

A

certain functional groups contain hydrogen bonding (alcohols, amides, carboxylic acids) and other dipole-dipole (ketones, aldehydes) and alkanes, alkenes have LDFs

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5
Q

Homolytic bond fission

A

a covalent bond between 2 atoms in a molecules breaks with each atom taking one electron from the bond
- forms radicals

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6
Q

Heterolytic bond fission

A

a covalent bond between 2 atoms in a molecule breaks with one atom taking both bonding electrons
- forms ions

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7
Q

What are the reactions with alkanes

A

combustion (complete&incomplete) and free radical substitution

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8
Q

Outline combustion with alkanes

A

complete combustion: in excess oxygen and carbon dioxide and water are produced
incomplete combustion: in lack of oxygen and carbon/carbon monoxide and water is produced

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9
Q

Outline free radical substitution

A

3 stages: initiation, propagation and termination
initiation: forming a radical
propagation: reacting a radical with non-radical
termination: forming a non-radical with 2 radical

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10
Q

What is the general equation for radical substitution

A

alkane + halogen → halogenoalkane + hydrogen halide

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11
Q

Why can alkenes undergo substation reactions and not alkanes

A

Molecules which contain π-bonds can undergo addition because they are unsaturated and since only the weaker π-bonds are broken rather than the strong sigma bonds addition reaction happens faster
- alkenes are more reactive than alkanes

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12
Q

Outline first step of free radical substitution

A
  1. Initiation (formation of radicals through homolytic bond fission + UV)
    Br2 —> Br• + Br•
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13
Q

Outline second step of free radical substitution

A
  1. Propagation (reacting a radical with a non radical)
    Br• + C2H6 —> HBr + C2H5•
    C2H5• + Br2 —> C2H5Br + Br•
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14
Q

Outline last step of free radical substitution

A
  1. Termination (forming non-radicals from radicals)
    Br• + Br• —> Br2
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15
Q

What is the general equation of free radical substitution

A

alkene + halogen –> halogenoalkane + hydrogen halide

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16
Q

What is the general formula of hydrogenation

A

alkene + hydrogen –> alkane

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17
Q

What are the conditions of hydrogenation

A

nickel catalyst + 150°C

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18
Q

What is the general formula of halogenation

A

alkene + halogen –> dihalogenoalkane

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19
Q

What is an example of halogenation

A

bromine test

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20
Q

What is the general formula of hydrohalogenation

A

alkene + hydrogen halide –> halogenoalkane
- weakest hydrogen halide bond reacts faster

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21
Q

What is the general formula of hydration

A

alkene + steam –> alcohol

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22
Q

What are the conditions for hydration

A

H2SO4 catalyst + heat + high pressure

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23
Q

What is the general formula of addition polymerisation

A

alkene –> polyalkane

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24
Q

List all the reactions of alkenes

A
  • hydration
  • hydrogenation
  • combustion
  • free radical substitution
  • halogenation
  • hydrohalogenation
  • addition polymerasation
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25
Q

What are the different types of alcohol

A
  • primary: the carbon to which the hydroxyl group is attached is attached to only 1 carbon
  • secondary:the carbon to which the hydroxyl group is attached is attached to 2 carbons
  • tertiary: the carbon to which the hydroxyl group is attached is attached to 3 carbons
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26
Q

Outline the oxidation of alcohols for primary alcohols

A

primary alcohols can form aldehydes
- further oxidised to carboxylic acids

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27
Q

What are the conditions for the oxidation of primary alcohols

A
  • acidified potassium manganate/dichromate
  • heat
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28
Q

Outline oxidation of secondary alcohols

A

they form ketones and water

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29
Q

Why do tertiary alcohols not oxidise

A

there no H atoms directly bonded to the C-OH

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30
Q

What is the general formula of esterification

A

alcohols + carboxylic acids –> ester + water

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31
Q

What are the conditions for esterification

A

H2SO4 catalyst

32
Q

Outline reaction with halogenalkanes

A

halogenalkane + sodium hydroxide –> alcohol + sodium halide

33
Q

What type of reaction is halogenalkanes

A

nucleophilic

34
Q

In general what type of reactions are addition reactions

A

electrophilic

35
Q

In general what type of reaction are substitution reactions

A

nucleophilic

36
Q

SN1 reaction features

A
  • tertiary halogenalkane
  • 2-step reaction
  • the heterolytic bond fission of the C-X is the RDS
  • reaction has an order of 1
  • nucleophilic substitution
37
Q

Outline SN1 reaction

A
  1. remove halogen (curly arrow)
  2. formation of carbonation + halogen -
  3. OH- bonds to +
  4. alcohol is formed
38
Q

general formula of SN1 reaction

A

halogenalkane + hydroxide ion –> halide ion +alcohol (tertiary)

39
Q

Features of SN2

A
  • primary halogenoalkane
  • 1 step reaction
  • reaction has an order of 2
  • nucleophilic substitution
  • heterolytic bond fission
40
Q

Outline SN2 reaction (features)

A
  • nucleophilic substitution
  • overall 2nd order
  • RDS = halogenoalkane + nucleophile
  • inverse configuration
  • slower
  • heterolytic bond fission
  • primary halogenoalkane
41
Q

general formula of SN2 reaction

A

halogenalkane + hydroxide –> halide ion + primary alcohol

42
Q

Factors that affect the rate of nucleophilic substitution

A
  • nucleophile ((the greater the electron density, the stronger the nucleophile, the faster the reaction)
  • halogenoalkane (the weaker the halogenoalkane the faster the reaction)
43
Q

Protic and aprotic solvents

A

SN1: protic
SN2: aprotic

44
Q

Why are halogenoalkanes more reactive than alkanes

A

halogenoalkanes: polar bonds, LDFs + dipole forces, polar molecules, more reactive
alkanes: non-polar bonds, non-polar molecules, LDFs, less reactive

45
Q

Define a nucleophile

A

donates a pair of electrons

46
Q

Define an electrophile

A

accepts a pair of electrons

47
Q

When does an addition reaction take place

A

unsaturated compound

48
Q

When does a substitution reaction take place

A

saturated compound

49
Q

what are the 2 types of oxidising agents for alcohols + colour change

A
  • acidified potassium dichromate (orange to green)
  • acidified potassium manganate (purple to colourless)
50
Q

Give an example of an electrophilic addition reaction

A

alkene + hydrogen halide

51
Q

What does Markovnikov’s rule state

A
  • the halogen needs to be bonded with the most substituted carbon atom
  • ex: secondary carbocations are more stable than primary carbocations
  • alkyl groups make compound more stable
52
Q

Give an example of an electrophilic substitution reaction

A

nitration of benzene

53
Q

What is the difference between ketone and aldehyde

A

ketone: RCOCR
aldehyde: RCHO

54
Q

What makes a compound trans or cis

A

they need to have 2 substituents groups

55
Q

Why is a protic solvent used for SN1 mechanisms

A

it solvates/stabilises the carbocation

56
Q

Why is an aprotic solvent used for SN2 mechanisms

A

it maintains the reactivity of the nucleophile

57
Q

What is the reagent used for the reduction of alcohol

A

LiAlH4 (for all)
NaBH4 (not for carboxylic acids)

58
Q

How to reduce carboxylic acid

A

aldehyde –> primary alcohol
LiAlH4

59
Q

How to reduce ketone

A

secondary alcohol
- LiALH4

60
Q

Outline the conditions for the reduction of aldehyde from carboxylic acid

A

have to use LiAlH4 refluxed in dry ether, followed by dilute acid

61
Q

What are structural isomers

A

functional groups and atoms are attached differently

62
Q

What are the two types of conformational isomers

A

staggered and eclipsed

63
Q

What is the main property of conformational isomers

A

they can be interconverted by rotation due to their sigma bond (carbon single bond)

64
Q

What are the characteristics of staggered conformational isomer

A

has angles between hydrogen atoms on adjacent carbons of 60°
- lower energy (more stable) because there is less electron repulsion because C-H bonds are far apart

65
Q

What are the characteristics of eclipsed conformational isomer

A

has 0° angle between H atims
- higher energy (less stable) because there is more electron repulsion because the C-H bonds are closer together

66
Q

What are the different types of configurational isomers

A

E/Z
optical isomers
cis & trans

67
Q

What is an aromatic compound

A

it has delocalised pi electrons in a ring

68
Q

Outline the reduction of nitrobenzene

A
  • benzene ring with NO2 on top
  • Sn/HCl reflux
  • NH3+ on top of benzene ring
  • NaOH
  • benzene ring with NH2
69
Q

Why does benzene undergo an electrophilic substitution reaction

A

it has delocalised electrons

70
Q

What is the difference between E and Z isomers

A

Z: have the highest priority groups on the same side of the C=C bond
E: have the highest priority groups on different side of the C=C bond

71
Q

What is a chiral carbon

A

a carbon that has 4 different groups attached to it

72
Q

What are the features of enantiomers

A

they are mirror images of each other but they can be superposed on top of each other

73
Q

What are Diastereomers

A

compounds that contain more than one chiral centre (not mirror images of each other)

74
Q

Properties of optical isomers

A

they have identical physical properties except for their ability to rotate the plane of polarised light

75
Q

what si a racemixture

A

a mixture containing equal amounts of each enantiomer

76
Q

What is the effect of polarised plane light on optical isomers

A

One enantiomer rotates light clockwise, the other rotates light anticlockwise

77
Q

Features of race mixtures

A
  • optically inactive
  • enantiomers will cancel out each other’s effect
  • the plane of polarised light will not change