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Chemistry IB > 10 Organic Chemistry > Flashcards

10 Organic Chemistry Flashcards

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1
Q

What is catenation and what is its role in organic chemistry?

A

This enables it to form long chains of carbon atoms, and hence an almost infinite variety of carbon compounds are known
The tendency of identical atoms to form covalent bonds with each other and hence form chains is known as catenation

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2
Q

What bonds can carbon form?

A

Carbon always forms four covalent bonds which can be single, double or triple bonds

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3
Q

What is a functional group and what is its role?

A

A functional group is a specific atom or group of atoms which confer certain physical and chemical properties onto the molecule
Organic molecules are classified by the dominant functional group on the molecule

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4
Q

What is a homologous series and how do compounds in one differ?

A

Organic compounds with the same functional group, but a different number of carbon atoms, are said to belong to the same homologous series
Every time a carbon atom is added to the chain, two hydrogen atoms are also added

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5
Q

What are the characteristics of a homologous series (5)?

A

Things we can say about a homologous series:
- each member has the same functional group
- each member has the same general formula
- each member has similar chemical properties
- each member differs by -CH2 -
- members have gradually changing physical properties, for example, boiling point, melting point and density

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6
Q

What happens as a homologous series ascends?

A

As a homologous series is ascended, the size of the molecule increases
This has an effect on the physical properties, such as boiling point and density

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7
Q

What is the boiling point graph for the first 8 alkananes?

A

increasing linearly with plateau

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8
Q

Why does boiling points increase with ascending homologous series for alkanes?

A

The broad trend is that boiling point increases with increased molecular size
Each additional -CH2 - (called the homologous increment ) adds 8 more electrons to the molecule
This increases the strength of the London Dispersion Forces
Stronger LDF leads to a higher boiling point
These trends are followed in other homologous series

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9
Q

What 4 formula can represent organic compounds?

A

Empirical Formulae
Molecular Formulae
Structural Formulae
Condensed Structural Formulae

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10
Q

What do empirical formulae show?

A

The empirical formula shows the simplest possible ratio of the atoms in a molecule

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11
Q

What is the molecular formula?

A

The molecular formula shows the actual number of atoms in a molecule
e.g. C4H10

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12
Q

What is the structural formula?

A

The structural formula shows the spatial arrangement of all the atoms and bonds in a molecule
This is also known as the displayed formula or graphical formula.
full drawing of molecule

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13
Q

What is the CONDENSED structural formula?

A

In a condensed structural formulae enough information is shown to make the structure clear, but most of the actual covalent bonds are omitted

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14
Q

How are condensed structural formulas shown?

A

Only important bonds are always shown, such as double and triple bonds
Identical groups can be bracketed together
Side groups are also shown using brackets
Straight chain alkanes are shown as follows:

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15
Q

What are structural isomers?

A

Structural isomers are compounds that have the same molecular formula but different structural formulae
Eg. propene and cyclopropane

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16
Q

What are the 3 different types of STRUCTURAL isomerism?

A

There are three different types of structural isomerism:
Branch-Chain isomerism
Positional isomerism
Functional group isomerism

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17
Q

What is branch-chain isomerism?

A

Branch-Chain isomerism is when compounds have the same molecular formula, but their longest hydrocarbon chain is not the same
This is caused by branching
Eg. pentane and 2,2-dimethylpropane

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18
Q

What is positional isomerism?

A

Positional isomers arise from differences in the position of a functional group in each isomer
The functional group can be located on different carbons
For example, butan-1-ol and butan-2-ol

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19
Q

What is functional group isomerism?

A

When different functional groups result in the same molecular formula, functional group isomers arise
The isomers have very different chemical properties as they have different functional groups
For example, butanol and ethoxyethane

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20
Q

What are saturated hydrocarbons?

A

Saturated hydrocarbons are hydrocarbons which contain single bonds only resulting in the maximum number of hydrogen atoms in the molecule

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21
Q

What are unsaturated hydrocarbons?

A

Unsaturated hydrocarbons are hydrocarbons which contain carbon-carbon double or triple bonds

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22
Q

What are hydrocarbons?

A

Hydrocarbons are compounds containing hydrogen and carbon only

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23
Q

What are the 4 families of hydrocarbons?

A

There are four families of hydrocarbons you should know: alkanes, alkenes, alkynes and arenes

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24
Q

What are the features of alkanes?

A

Alkanes have the general molecular formula CnH2n+2. They contain only single bonds and are said to be saturated

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25
Q

What is the general formula of alkenes?

A

Alkenes have the general molecular formula CnH2n

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26
Q

Are alkenes saturated/unsaturated?

A

They are said to be unsaturated

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27
Q

How are alkenes named?

A

Alkenes are named using the nomenclature rule alk + ene
In molecules with a straight chain of 4 or more carbon atoms, the position of the C=C double bond must be specified
The carbon atoms on the straight chain must be numbered, starting with the end closest to the double bond
The lowest-numbered carbon atom participating in the double bond is indicated just before the -ene:

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28
Q

What is the difference between the functional group and the name of the family for alkenes?

A

There is a distinction to be made between the name of the functional group and the name of the family
The name of the family is alkene, but the name of the functional group is alkenyl

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29
Q

What is the general formula of alkynes? Are they (un)saturated?

A

Alkynes have the general molecular formula CnH2n-2
The triple bond makes them unsaturated molecules

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30
Q

How are alkynes named?

A

Alkynes are named using the nomenclature rule alk + yne
As with alkenes, in molecules with a straight chain of 4 or more carbon atoms, the position of the triple bond must be specified
The carbon atoms on the straight chain must be numbered, starting with the end closest to the triple bond
The lowest-numbered carbon atom participating in the triple bond is indicated just before the -yne:

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31
Q

What is the name of the functional group for alkenes?

A

The name of the functional group is alkynyl

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32
Q

What is an arene?

A

Arene is the collective name given to compounds with one or more rings with pi electrons that are delocalised throughout the ring(s)

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33
Q

What are compounds with rings called?

A

Compounds with this feature are said to be aromatic
This doesn’t mean they are necessarily smelly, although a lot of naturally occurring arenes do have distinctive smells!

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34
Q

What is benzene and what is its functional group, v. brief?

A

Benzene, C6H6, is the only aromatic hydrocarbon that is covered in IB Chemistry and is dealt with in Section 10.1.12
The functional group in benzene is known as a phenyl group when attached to other molecules

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35
Q

What is the general formula of halogenoalkanes?

A

Halogenoalkanes or Haloalkanes have the general molecular formula, CnH2n+1X, where X represents a halogen

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36
Q

How are halogenoalkanes named?

A

Haloalkanes are named using the prefix chloro-, bromo- or iodo-, with the ending -ane
In molecules with a straight chain of three or more carbon atoms, the position of the halogen atom must also be specified
The carbon atoms on the straight chain must be numbered, starting with the end closest to the halogen atom
The number of the carbon atom attached to the halogen is indicated before the prefix

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37
Q

How are halogenoalkanes named if they have more than one halogen?

A

The position of all halogens in dihaloalkanes except those with one carbon atom must be specified.
If there is more than one of the same type of halogen atom on the molecule, the di (two), tri (three) or tetra (four) prefixes must also be used

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38
Q

What are alcohols i.e. functional group?

A

Alcohols are a family of molecules that contain the hydroxyl functional group, -OH

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39
Q

What is the general formula fo alcohols?

A

Their general formula is CnH2n+1OH

40
Q

How are alcohols named?

A

The nomenclature of alcohols follows the pattern alkan + ol
If there are two -OH groups present the molecule is called a diol

41
Q

How can alcohols be classified?

A

Alcohols are classified as primary, secondary or tertiary depending on the number of carbons attached to the functional group carbon
This is covered in detail in Section 10.1.11

42
Q

What are ethers?

A

Ethers are a family of molecules that contain the ether functional group, R-O-R, where R is an alkyl group

43
Q

What is the general formula of ethers?

A

Their general formula is CnH2n+2O

44
Q

How are ethers named?

A

The nomenclature of ether follows the pattern alkoxy + alkane

45
Q

What are ethers functional group isomers of?

A

Ethers are functional group isomers of alcohols

46
Q

What are carbonyls?

A

Carbonyl is the collective name for compounds containing the functional group C=O

47
Q

What is the general formula of a carbonyl?

A

The general formula of a carbonyl is CnH2nO

48
Q

What are the two sub-families of carbonyl?

A

The two sub-families of carbonyls are aldehyde and ketone (known in some countries as alkanals and alkanones)

49
Q

What is an aldehyde, how is the formula written and why?

A

If the carbonyl group is on the end of a chain then it is an aldehyde and has the functional group formula, RCHO
the H is written before the O so as not to confuse it with an alcohol

50
Q

How are aldehydes named?

A

The nomenclature of carbonyls follows the pattern alkan + al
There is no need to use numbers in the name as aldehyde will always be on the number 1 carbon atom

51
Q

What is the functional group of ketones?

A

Ketones have a minimum of three carbons and have the general functional group formula, RCOR

52
Q

How are ketones named?
When must numbering start?

A

The nomenclature of ketones follows the pattern alkan + one
After butanone, the carbonyl group can have positional isomers, so numbering must be used
For example pentan-2-one and pentan-3-one

53
Q

Do aldehydes and ketones show similar reactions?

A

YES
As they have a very similar functional group arrangement, aldehydes and ketones show similar chemical reactions

54
Q

Despite their similar reactions, why do aldehydes and ketones have different reactivities?

A

Differences in their chemistry are due to the reactions that involve the H on the aldehyde or the nature of the R group

55
Q

Why do carbonyls have such high boiling points?

A

The difference in electronegativity between oxygen and carbon means the C=O is polar, leading to dipole-dipole attractions between the molecules which results in:
higher than expected boiling points for small molecules
solubility in water for the lower members of the families

56
Q

What do aldehydes and ketones with the same number of carbons exhibit?

A

Aldehydes and ketones with the same number of carbons are functional group isomers

57
Q

What are carboxylic acids?

A

Carboxylic acids is the name given to compounds containing the functional group carboxyl, -COOH

58
Q

What is the general formula of a carboxylic acid?

A

The general formula of a carboxylic acid is CnH2n+1COOH which can be shortened to just RCOOH

59
Q

How are carboxylic acids named?

A

The nomenclature of carboxylic acid follows the pattern alkan + oic acid
There is no need to use numbers in the name as the carboxyl group will always be on the number 1 carbon atom

59
Q

How are carboxylic acids named?

A

The nomenclature of carboxylic acid follows the pattern alkan + oic acid
There is no need to use numbers in the name as the carboxyl group will always be on the number 1 carbon atom

60
Q

What are esters?

A

Esters are functional group isomers of carboxylic acids and contain the functional group, carboxylate, -COOR

61
Q

What is the general formula of an ester?

A

The general formula of an ester is usually represented as RCOOR where R can be the same or different on either side of the carboxylate group

62
Q

How are esters named? What is the alkyl group?

A

The nomenclature of esters follows the pattern alkyl + alkanoate
The alkyl group in the name is the R group attached to the oxygen

63
Q

What similarities do carboxylic acids and esters have?

BOILING AND MELTING POINTS

A

H-bonds are present between carboxylic acid molecules and not between esters, so this affects the melting point, boiling point and solubility:
Smaller chain carboxylic acids are soluble in water and have higher boiling points than expected (e.g. ethanoic acid is 117 oC)
Esters are insoluble in water and have lower boiling points than their isomeric carboxylic acids ( e.g. methyl methanoate is 31 oC)

64
Q

What are the three organic nitrogen-containing families?

A

There are three organic nitrogen families that you need to know: amines, amides and nitriles

65
Q

What are amines?

A

Amine is the name given to compounds containing the functional group amino, -NH2

66
Q

What are amines derived from?

A

Amines are derived from ammonia where one H in ammonia (NH3)has been replaced by an R (alkyl) group

67
Q

What is the general formula of amines?

A

The general formula of an amine is CnH2n+1NH2 which can be shortened to just RNH2

68
Q

How are amines named?

A

The nomenclature of an amine follows the pattern alkyl + amine or amino + alkane
E.g. propylamine or aminopropane

69
Q

What is an amide?

A

Amide is the name given to compounds containing the functional group carboxamide, -CONH2

70
Q

What are amides a combination of?

A

Amides are a combination of amino and carbonyl groups

71
Q

What is the general formula of an amide?

A

The general formula of an amide is CnH2n+1CONH2 which can be shortened to just RCONH2

72
Q

How are amides named?

A

The nomenclature of an amide follows the pattern alkan + amide

73
Q

What are nitriles?

A

Nitriles are compounds containing the functional group nitrile, -CN

74
Q

What is the CN group of the nitrile also called?

A

This is the same CN group that is called a cyanide group as an ion, just as hydroxyl group, OH is called hydroxide in inorganic chemistry

75
Q

What is the general formula fo. a nitrile?

A

The general formula of an nitrile is CnH2n+1CN which can be shortened to just RCN

76
Q

How are nitriles named?

A

The nomenclature of a nitrile follows the pattern alkane + nitrile (some people leave out the ‘e’ on the alkane)
E.g ethanenitrile or ethannitrile

77
Q

What are primary alcohols/halogenoalkanes?

A

Primary alcohols and halogenoalkanes are those in which the carbon atom bonded to the functional group is attached to one other carbon atom (or alkyl group)

78
Q

What are secondary alcohols/halogenoalkanes?

A

In secondary alcohols and halogenoalkanes the functional group carbon atom is attached to two other carbon atoms (or alkyl groups)

79
Q

What are tertiary alcohols/halogenoalkanes?

A

In tertiary alcohols and halogenoalkanes the functional group carbon atom is attached to three other carbon atoms (or alkyl groups)

80
Q

Do amines follow the same pattern as alcohols/halogenoalkanes in terms of primary/secondary etc?

A

Amines follow a slightly different classification system, although the terms primary, secondary and tertiary are still used

81
Q

What is the classification of nitriles based on?

A

The classification is based on the number of alkyl groups attached to the nitrogen in the amine

82
Q

What are primary amines?

A

Primary amines are those in which the nitrogen is attached to one other carbon atom (or alkyl group)

83
Q

What are secondary amines?

A

In secondary amines the nitrogen atom is attached to two other carbon atoms (or alkyl groups)

84
Q

What are tertiary amines?

A

In tertiary amines the nitrogen is attached to three other carbon atoms (or alkyl groups)

85
Q

What did kekule suggest benzene was?

A

Kekulé suggested that benzene was a hexagon with three double bonds
It was therefore equivalent to three ethene molecules

86
Q

What should therefore benzene have similar chemical properties to and why does it not?

A

However, this turned out not to be the case
Ethene undergoes addition reactions whereas benzene rarely does (only under very harsh conditions) and instead undergoes substitution reactions

87
Q

How do benzene bonds differ/are similar from ethene bonds and how?

A

The presence of three double bonds also suggested that benzene had shorter double and longer single bonds
In fact, the bond lengths in benzene were exactly the same
They were found to be an intermediate between single and double bonds

88
Q

How does the stability of benzene also differ?

A

The benzene is also much more stable than Kekulé’s suggested structure for benzene
Less energy was required to hydrogenate a benzene molecule compared to the hydrogenation of three ethene molecules
This means that the bonds broken in benzene are stronger than the double bonds in ethene

89
Q

What is the increased stability of benzene called?

A

The increase in stability of benzene is known as the delocalisation energy and is caused by the delocalised electrons in the benzene structure

90
Q

Why is the bond length between single and double bonds in benzene?

A

The C-C in benzene are an intermediate between single and double bonds which is a result of these delocalised electrons

91
Q

What is the structure of benzene? Why are all bonds identical?

A

Benzene is a planar regular hexagon with bond angles of 120º
All the bonds are identical due to the delocalization of electrons

92
Q

What bonds does each carbon atom have in benzene?

A

Each sp2 hybridised carbon atom in benzene forms:
A σ bond with two other carbons
A σ bond with one hydrogen atom

93
Q

What orbitals overlap in benzene?

A

The remaining p orbital is overlapping with the p orbitals on both sides of it
To achieve maximum overlap, the benzene ring must be planar

94
Q

What does the overlapping of p orbitals in benzene form?

A

This results in the formation of a system of π bonds spread out over the whole ring

95
Q

Therefore how are electrons located in benzene?

A

Due to this, the electrons are not bound to specific atoms but can instead freely move around the structure and are said to be delocalised

Chemistry IB (13 decks)

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