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Chemistry HL > Organic Chemistry (topic 10/20) > Flashcards

Organic Chemistry (topic 10/20) Flashcards

1
Q

Homologous series

A

A series of compounds of the same family, with the same general formula, which differ from each other by a common structural unit.

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2
Q

Structural isomers

A

Compounds with the same molecular formula but different arrangements of atoms.

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3
Q

Functional groups

A

Single or groups of atoms that dictate the properties of a group of organic compounds. The reactive parts of molecules.

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4
Q

Saturated compounds

A

Contain single bonds only

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5
Q

Unsaturated compounds

A

Contain double or triple bonds.

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6
Q

Alkanes

A

Alkanes have low reactivity and undergo free-radical substitution reactions.

  • Function group: alkyl
  • Saturated compound
  • General formula: CnH2n+2

Naming Alkanes
- [stem] + ane
ex. propane, butane, methane, etc.

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7
Q

Alkenes

A

Alkenes are more reactive than alkanes and undergo addition reactions. Bromine water can be used to distinguish between alkenes and alkanes.

  • Functional group: alkenyl (double carbon bond)
  • Known as unsaturated compound
  • General formula: CnH2n

Naming Alkenes
- [stem] + ene
ex. hexene, butene, etc.

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8
Q

Alcohols

A

Alcohols undergo nucleophilic substitution reactions with acids (also called esterification or condensation) and some undergo oxidation reactions.

  • Functional group: OH (hydroxyl group)
  • General formula: CnH2n+1OH

Naming Alcohols
- [stem] + nol
ex. propanol, decanol, etc.

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9
Q

Halogenoalkanes

A

Halogenoalkanes are more reactive than alkanes. They can undergo (nucleophilic) substitution reactions. A nucleophile is an electron-rich species containing a lone pair that it donates to an electron-deficient carbon.

  • Formed when a halogen is bonded to an alkyl group
  • Functional group: R - X (R being the alkyl group and X being any halogen)
  • General formula: CnH2n+1X

Naming Halogenalkanes
- Chloro- /bromo- /iodo- + [alkane]
ex. Bromoethane, iodobutane, etc.

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10
Q

Polymers

A

Addition polymers consist of a wide range of monomers and form the basis of the plastics industry.

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11
Q

Benzene

A

Benzene does not readily undergo addition reactions but does undergo electrophilic substitution reactions. Is an aromatic, unsaturated hydrocarbon.

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12
Q

The different characteristics of a homologous series include:

A
  • Members have a functional group
  • Molar mass of consequent members differ by 14 kJ mol-1
  • Consequent members differ by CH2 group
  • Members show gradual trend in physical properties
  • Members have similar chemical properties
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13
Q

Empirical formula

A

Is the simplest whole-number ratio of atoms in a compound.

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14
Q

Molecular formula

A

Represents the real number of atoms and each type of atom in a compound.

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15
Q

Full structural formulae

A

All atoms and bonds between all atoms are shown.

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16
Q

Condensed structural formulae

A

Assumes certain bonds and therefore all atoms need not be shown. Easier to draw.

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17
Q

Skeletal formulae

A

Removes all atoms, leaving only a ‘skeleton’ of the molecule.

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18
Q

Stereochemical formulae

A

Shows the three-dimensional positions of atoms around a carbon.

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19
Q

Alkynes

A
  • Functional group: alkynyl (triple carbon bond)
  • Known as saturated compound
  • General formula: CnH2n-2

Naming Alkynes
- [stem] + yne
ex. butyne, propyne, etc.

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20
Q

Aldehydes

A
  • Functional group: CHO (aldehyde group)
    General formula: CnH2n+1CHO

Naming aldehydes
- [stem] + al
ex. butanal, pentanal.

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21
Q

Ketones

A
  • Functional group: -CO- (ketone)
  • General formula: CnH2n+1COCxH2x+1 (where x and n are two positive intergers)

Naming Ketones
- [stem] + anone
ex. ethanone, hexanone, etc.

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22
Q

Carboxylic acids

A
  • Functional group: -COOH (carboxyl)
  • General formula: CnH2n+1COOH

Naming Carboxylic acids
- [stem] + oic acid
ex. propanoic acid, butanoic acid, etc.

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23
Q

Ethers

A
  • Functional group: -O- (ether)
  • General formula: CnH2n+1OCmH2m+1 (where m and n are two positive integers)

Naming Ethers
- [stem of shorter carbon chain] + oxy + [stem of longer carbon chain] + ane
ex. methoxypropane, ethoxyethane, etc.

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24
Q

Esters

A
  • Functional group: -COO- (ester)
  • General formula: CnH2n+1COOCmH2m+1 (where n and m are two positive integers)

Naming Esters
- [stem of alcohol] + yl + [stem of carboxylic acid] + noate
ex. methyl methanoate, ethyl propanoate, etc.

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25
Q

Amines

A
  • Functional group: -NH2
  • General formula: CnH2n+1NH2

Naming Amines

  • Primary Amines
  • Secondary Amines
  • Tertiary Amines
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26
Q

Primary Amines

A
  • Contain only one carbon connected to the nitrogen in the compound
  • [stem] + amine
    ex. propanamine, butanamine, etc.
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27
Q

Secondary Amines

A
  • Contain two carbons connected to the nitrogen in the compound
  • N-[stem of shorter carbon chain] + yl + [stem of longer carbon chain] + amine
    ex. N-methylbutanamine, N-ethylpropanaimine, etc.
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28
Q

Tertiary Amines

A
  • Contain three different carbon bonds connected to the nitrogen in the compound.
  • N-[stem of shortest carbon chain] + yl + N-[stem of shorter carbon chain] + yl + [stem of longest carbon chain] + amine
    ex. N, N-diethylpropanamine, N-propyl-N-butylhexanamine.
29
Q

Amides

A
  • Functional group: -CONH2 (carboxamide or amido)
  • General formula: CnH2n+1CONH2

Naming Amides

  • Primary Amides
  • Secondary Amides
  • Tertiary Amides
30
Q

Primary Amides

A
  • Contain only one carbon bonded to the nitrogen
  • [stem] + amide
    ex. butanamide, propanamide, etc.
31
Q

Secondary Amides

A
  • Contain two carbon atoms bonded to the nitrogen
  • N-[stem of shorter carbon chain] + yl + [stem of longer carbon chain] + amide
    ex. N-butylhexanamide, N-propylpentanamide, etc.
32
Q

Tertiary Amides

A
  • Contain three different carbon bonds connected to the nitrogen in the compound
  • N-[stem of shortest carbon chain] + yl + N-[stem of shorter carbon chain] + yl + [stem of longest carbon chain] + amide
    ex. N, N-diethylpropanamide, N-propyl-N-butylhexanamide
33
Q

Nitriles

A
  • Functional group: -CN (nitrile)
  • General formula: CnH2n+1CN

Naming Nitriles
- The carbon from the nitrile group counts as the first carbon of the chain
- [stem] + ane + nitrile
ex. ethanenitrile, propanenitrile

34
Q

Areles

A
  • Functional group: phenyl
  • General formula: C6H5
  • Prefix: -phenyl or Suffix: -benzene
35
Q

Structural Isomers

A

Compounds with the same molecular formula but a different structure and arrangement of atoms. Have the similar chemical properties but different physical properties such as melting and boiling points.

36
Q

Chain Isomers

A

Occur when a molecule can have its functional group in different positions in the molecule. When it can alter its longest carbon chain.

37
Q

Functional Group Isomerism

A

Occur when a molecule has the same molecular formula but two different functional groups.

38
Q

Volatility

A

How fast a molecule evaporates and is determined by the molecule’s boiling point.

39
Q

Three factors that influence the volatility and boiling point of a substance

A
  1. Molar mass
  2. Surface Area
  3. Nature of a functional group
40
Q

Molar mass influencing the volatility and boiling point of a substance

A
  • As molar mass increases
  • Strength of London Dispersion forces increase
  • Energy required to break the intermolecular bonds between between a molecule increases
  • Boiling point increases
41
Q

Surface Area influencing the volatility and boiling point of a substance

A
  • Branch-chained isomers have a smaller surface area and so they have less contact with other molecules.
  • Strength of London Dispersion forces decreases compared to straight-chain isomers.
  • Energy required to break the intermolecular bonds between a molecule decreases.
  • Boiling point decreases
42
Q

Nature of a functional group influencing the volatility and boiling point of a substance

A
  • Polar functional groups result in stronger dipole-dipole interactions and therefore require higher amounts of energy to break the bonds, leading to higher boiling points
  • Some molecules, such as alcohols and carboxylic acids can form hydrogen bonds and therefore have even higher boiling points.
43
Q

Primary Alcohols

A

Have only one carbon atom directly bonded to carbon that is bonded to the functional group.

44
Q

Secondary alcohols

A

Have two carbon atoms directly bonded to carbon that is bonded to the functional group.

45
Q

Tertiary alcohols

A

Have three carbon atoms directly bonded to carbon that is bonded to the functional group.

46
Q

Primary Halogenoalkanes

A

Have only one carbon atom directly bonded to carbon that is bonded to the functional group. Similar to primary alcohols.

47
Q

Secondary Halogenoalkanes

A

Have two carbon atoms directly bonded to carbon that is bonded to the functional group. Similar to secondary alcohols.

48
Q

Tertiary Halogenoalkanes

A

Have three carbon atoms directly bonded to carbon that is bonded to the functional group. Similar to tertiary alcohols.

49
Q

Primary amides and amines

A

Have only one carbon atom directly bonded to the amide or amine functional group.

50
Q

Secondary amides and amines

A

Have two carbon atoms directly bonded to the amide or amine functional group.

51
Q

Tertiary amides and amines

A

Have three carbon atoms directly bonded to the amide or amine functional group.

52
Q

Alkane-related reactions

A

Since Alkanes are saturated hydrocarbons, they undergo substitution reactions.

Carbon-hydrogen bond is non-polar which means it is more stable since charge distribution is not unequal.

  1. Combustion reaction
  2. Free-radical substitution reactions
53
Q

Combustion reaction

A

Alkanes undergo combustion in the presence of oxygen. They undergo two types of combustion:

  1. Complete combustion
    • This occurs in the presence of excess oxygen. Ex. C3H8(g) + 5O2(g) -> 3CO2(g) + 4H2O(l)
    • It results in carbon dioxide and water.
  2. Incomplete combustion
    • This occurs in the presence of insufficient oxygen. Ex. C3H8(g) + 7O2(g) -> 6CO(g) + 8H2O(l)
    • It results in the formation of carbon monoxide/carbon and water
54
Q

Free radical substitution reactions

A
  • Alkanes react with halogens in free-radical substitution reactions
  • The condition for this reaction is UV light
  • The reaction can be divided into 3 parts
    1. Initiation
      • In this step, the chlorine (or any halogen) undergoes photochemical homolytic bond fission and forms radicals of chlorine, which are very reactive.
        Ex. Cl2 -> 2Cl
    2. Propagation
      • In this step, the free-radical chlorine reacts with an alkane to form an alkane radical.
      • This alkane radical reacts with a chlorine free-radical again to form a halogenoalkane.
        Ex. Cl* + CH4 -> CH3* + HCl
        CH3* + Cl2 -> CH3Cl + Cl
      • The net amount of radicals remains the same as a radical is used and a radical is produced in every reaction
    3. Termination
      • In this step, two free-radicals combine again to form the original molecules and new molecules.
      • All free-radicals are terminated
        Ex. Cl* + Cl* -> Cl2
        CH3* + CH3* -> C2H6CH3Cl -> CH3Cl
55
Q

Alkene-related reactions

A

Alkenes are unsaturated and undergo addition reactions where the double-bond is broken.

In addition reactions, two smaller molecules react to form one bigger molecule.

  1. Hydrogenation
  2. Halogenation
  3. Hydrogen halides
  4. Hydration
  5. Polymerisation
56
Q

Hydrogenation

A
  • Occurs when an alkene reacts with hydrogen to form an alkane.
  • The conditions for this reactions are Ni and 150 degrees C.
    Ex. C2H4 + H2 -> C2H6
57
Q

Halogenation

A
  • Occurs when an alkene reacts with a halogen gas.
    Ex. C2H4 + Br2 -> C2H4Br2
58
Q

Hydrogen halides

A
  • Hydrogen halides react with alkenes to form halogenoalkanes.
    Ex. C2H4 + HBr -> C2H5Br
59
Q

Hydration

A
  • Alkenes react with water to form alcohols.
  • The conditions for this reaction are steam and concentrated H2SO4.
    Ex. C2H4 + H2O -> C2H5OH
60
Q

Polymerisation

A
  • Polymerisation occurs when many alkenes join to form a polymer.
61
Q

Alcohol-related reactions

A

Alcohols are saturated and undergo substitution reactions as well as some other reactions.

Combustion of alcohols

Oxidation of alcohols

Esterification

62
Q

Combustion of alcohols

A
  • Alcohols, in excess oxygen, combust to form carbon dioxide and water.
    Ex. 2CH3OH + 3O2 -> 2CO2 + 4H2O
63
Q

Oxidation of alcohols

A
  • Alcohols can be oxidised by oxidising agents such as acidified potassium dichromate [Cr2(O7)^2-], which is accompanied with a color change from orange to green as it is reduced to Cr^3+.
  • Depending on the type of alcohol, different products are formed.
  1. Primary alcohols
  2. Secondary alcohols
  3. Tertiary alcohols
64
Q

Oxidation of primary alcohols

A
  • Primary alcohols undergo partial oxidation to form an aldehydes, after which they form a carboxylic acid.
  • For these reactions, heat under reflux (to allow the alcohol and the oxidising agent to remain in contact for a longer time) is required with an excess of the oxidising agent.
65
Q

Oxidation of secondary alcohols

A
  • Secondary alcohols form a ketone.
  • The conditions for this reaction are heat under reflux with a suitable oxidising agent.
66
Q

Oxidation of tertiary alcohols

A
  • Since they have no hydrogen atom directly bonded to the carbon atom that is bonded to the functional group, they do not undergo oxidation.
67
Q

Esterification

A
  • Esters are formed when an alcohol reacts with a carboxylic acid.
  • In the name of the compound, the alkyl group of the alcohol comes first and the alkyl group of the carboxylic acid comes second.
  • So, methanol and propanoic acid would form methyl propanoate.
68
Q

Halogenoalkane-related reactions

A

Halogenoalkanes undergo substitution reactions.

A nucleophile is a species that is rich in electrons and has a lone pair of electrons, which means it is attracted to molecules with positive charge.

Nucleophilic substitution reaction to form alcohol
- In the halogenoalkane molecule, the halogen is a nucleophile due to the three lone pairs that it has.
- So, the carbon (which has a partial positive charge in the bond) undergoes heterolytic bond fission with the halogen where the halogen takes the bonding electrons.
- In general, in heterolytic bond fission, a bond breaks and one atom takes both the bonding electrons from the covalent bond. This forms oppositely charged ions.
- The reaction that takes place is known as a nucleophilic substitution reaction as the nucleophilic halogen is separated from the halogenoalkane and replaced by another nucleophilic ion.
- The nucleophilic halogen gains a negative charge after being separated as it takes both the bonding electrons.
- Strong bases or alkalis like NaOH are reacted with halogenoalkanes as they contain a nucleophilic species, OH- , which has a lone pair of electrons (hence nucleophilic).
- The OH- ion substitutes the halogen, and the halogenoalkane is converted to an alcohol.
- The reaction conditions for the conversion of a halogenoalkane to an alcohol are heat and a dilute solution of sodium or potassium hydroxide.

CH3CH2CH2Cl + NaOH -> CH3CH2CH2OH + NaCl

  • As seen by the reaction, the halogenoalkane 1-chloropropane is converted to the primary alcohol propanol with the by-product of sodium chloride as chlorine is substituted for OH-.
69
Q

Benzene-related reactions

A
  • Benzene undergoes substitution reactions to maintain its stable structure.
  • The ring of delocalised electrons in benzene represent a region of electron density.
  • Therefore, electrophilic species are attracted to benzene due to its ring of delocalised electrons.
  • So, benzene undergoes electrophilic substitution reactions.
  • An electrophile is an electron-deficient species that has a partial positive or completely positive charge.

Nitration
- Benzene reacts with the nitronium ion (NO2)+ in an electrophilic substitution reaction to form nitrobenzene.
- In this reaction, the nitronium ion acts as the electrophile.
- The catalyst for this reaction is concentrated sulfuric acid (H2SO4)

Halogenation
- Benzene also undergoes electrophilic substitution reactions with halogens.
- For example, chlorine reacts with benzene to form chlorobenzene and hydrogen chloride. The catalyst for this reaction is aluminium chloride.
- In general, halogens react with benzene to form chloro- , fluoro- iodo- , bromo- benzene with the byproduct of a hydrogen halide (the halide that benzene reacted with). The catalyst, in general, will be aluminium halide (the halide that reacted with benzene).

Combustion of benzene
- Like all hydrocarbons, benzene also undergoes combustion in the presence of excess oxygen.
2C6H6 + 15O2 -> 12CO2 + 6H2O

Chemistry HL (20 decks)

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