3.3.1.3 Isomerism Flashcards

1
Q

What is isomerism?

A

When 2 or more compounds have the same molecular formula but differ in some other way

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2
Q

What is structural isomerism?

A

Same molecular formula, but different structural, displayed or skeletal formula

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3
Q

What is stereoisomerism?

A

Compounds/molecules with the same structural formula but with different atoms/bonds/groups arranged differently in space

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4
Q

What are the 3 types of structural isomers?

A

Chain isomers
Positional isomers
Functional group isomers

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5
Q

What is chain isomerism?

A

When there is more than one way of arranging atoms in the longest chain

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6
Q

What are the properties of chain isomerism?

A

Straight chains can pack closer together, so stronger Van der Waal forces, so higher m.p./b.p..
Branched chains cannot pack as close together so less surface area in contact, so weaker Van der Waal forces so lower m.p./b.p.

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7
Q

What is positional isomerism?

A

Positional isomers have the same carbon chain and the same functional group, but it is attached at different points along the carbon chain.

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8
Q

What is functional group isomerism?

A

Same molecular formula, but different functional group

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9
Q

What are the functional group isomer pairs?

A

Alkenes and cycloalkAnes
Aldehydes and ketones
Carboxylic acids and esters

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10
Q

What are the two types of stereoisomers?

A

E-Z Isomers
Optical isomers (a-level)

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11
Q

Why do E-Z isomers exist?

A

The double bond causes restricted rotation, so molecules cannot change structure, as this would require energy to break the double bond, which is not available at room temperature.

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12
Q

What are the Cahn-Ingold-Prelog (CIP) rules?

A

The higher the atomic number bonded to the carbons in the double bond, the higher the ranking. Priority groups are on the same side = Z isomer, opposite sides = E isomer

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