DF 9: What do the molecules look like? Flashcards

1
Q

What is an isomer?

A

Molecules which have the same molecular formula but the atoms are arranged differently

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2
Q

What are structural isomers?

A

Structural isomers have the same molecular formula but different structural arrangement of atoms

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3
Q

What are stereoisomers?

A

The order of bonding is the same, but the arrangement of the atoms in space is different in each isomer

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4
Q

What do structural isomers have?

A

Different structural arrangements of atoms

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5
Q

How can organic compounds be arranged?

A
General formula
Molecular formula
Shortened structural formula
Structural formula
Skeletal formula
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6
Q

What is general formula?

A

A formula that can describe any member of a family of compounds (Example - the general formula for alcohols is CnH2n+1)

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7
Q

What is molecular formula?

A

The actual number of atoms of each element in a molecule (such as C4H10)

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8
Q

What is shortened structural formula?

A

Shows the atoms, carbon by carbon, with the attached hydrogens and functional groups (Such as CH3CH2CH2CH2CH3)

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9
Q

What is structural formula?

A

Shows how all the atoms are arranged and all the bonds between them

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10
Q

What is skeletal formula?

A

Shows the bonds of the carbon skeleton only, with any functional groups

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11
Q

What are the different types of structural isomers?

A

Chain Isomerism

Positional Isomerism

Functional Isomerism

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12
Q

Chain Isomerism

A

These isomers have similar chemical properties, but their physical properties like boiling point will be different because of the change in shape of the molecule

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13
Q

Positional Isomerism

A

They also have different physical properties and their chemical properties might be different too!

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14
Q

Functional Isomerism

A

They have very different physical and chemical properties

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15
Q

What is the relationship between an increase in the number of carbon atoms in the chain increases and the number of possible isomers?

A

As the number of carbon atoms increases the number of possible isomers increases

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16
Q

How can position isomerism occur?

A

When there is an atom, or group of atoms, substituted in a carbon chain or ring (these are called functional groups).

Position isomerism occurs when the functional group is situated in different positions in the molecules.

17
Q

What are the two ways that atoms can be arranged differently in isomers.

A

The atoms are bonded together in a different order in each isomer (STRUCTURAL ISOMERS)

The order of bonding in the isomers is the same, but the arrangement of the atoms in space is different in each isomer (STEREOISOMERS)

18
Q

What do CH4, C2H6 and C3H8 have in common (isomers)

A

There is only one possible isomer for them

19
Q

Chain isomerism

A

The carbon skeleton can be arranged differently, for example a straight chain or a branched in different ways

20
Q

Positional isomerism

A

The skeleton and the functional group could be the same, only with the functional group attached to a different carbon atom

21
Q

Functional Isomerism

A

The same atoms can be arranged into different functional groups

22
Q

What are the two types of stereoisomers?

A
Geometric isomers
Optical isomers (Shapes)
23
Q

Geometric isomers

A

They are also known as E/Z Isomers

24
Q

Why do stereoisomers typically only apply to alkenes and not alkanes?

A

Alkanes dont contain any double bonds, single bonds allow atoms to rotate freely (Not stereoisomers)

Alkenes have at least one double bond, double bonds don’t allow the atoms to rotate so it is FIXED.

25
Q

How can alkenes be stereoisomers if they have a fixed double bond?

A

Alkenes still contain single bonds in their molecules which means atoms can rotate and therefore the RESTRICTED rotation around the C-C double bonds is what causes E/Z isomerism.

26
Q

What is an ‘E’ isomer?

A

‘E’ means opposite and corresponds to the term ‘trans’ which means both

27
Q

What is a ‘Z’ isomer?

A

‘Z’ means together and corresponds to the term ‘cis’

28
Q

How do the above rules of ‘E’ and ‘Z’ isomerism work?

A

This rule works when either of the two groups on either end of the double bond are the same or there is a hydrogen on both carbons.

29
Q

What is E/Z Isomerism all about?

A

Having 2 Hydrogens singly bonded to both carbon atoms

30
Q

What is trans/cis isomerism all about?

A

trans/cis isomerism can be used when you don’t have two hydrogens

31
Q

Naming alcohols

A

Find the longest carbon chain (Name it)

Determine the position of the alcohol group (OH) by counting the carbons to give the lowest number

Add ‘ol’ to the end of the name