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C14- ALKENES > 14.2- REACTION OF ALKENES > Flashcards

14.2- REACTION OF ALKENES Flashcards

1
Q

Are alkenes used as fuels?

A

no

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2
Q

Why are alkenes not used as fuels?

A

their reactivity makes them very useful for other purposes

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3
Q

What is the reaction of alkenes typically?

A

electrophilic additions

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4
Q

What makes the carbon-carbon double bond a centre of high electron density?

A

the four electrons in the carbon-carbon double bond

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5
Q

What are electrophiles attracted towards on an alkene?

A

carbon-carbon double bond which is the centre of electron density

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6
Q

What can electrophiles use to bond with alkenes?

A

by using two of the four electrons in the carbon-carbon double bond

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7
Q

Where do hydrogen halides add on an alkene?

A

across the double bond

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8
Q

When hydrogen halides add across the double bond of an alkene, what is formed?

A

halogenoalkane

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9
Q

What can happen when the double bond is not exactly in the middle when a hydrogen halide is added?

A

there are two possible products

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10
Q

What do the alkyl groups have a tendency to do?

A

release electrons

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11
Q

What is the tendency of the alkyl groups to release electrons called?

A

positive inductive effect

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12
Q

How is the positive inductive effect sometimes represented?

A

by an arrow along their bonds to show the direction of the release

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13
Q

What does the electron-releasing affect of the alkyl groups tend to do to the intermediate carbocation?

A

stabilise the positive charge of the intermediate carbocation

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14
Q

What is the affect on the carbocation the more the alkyl groups attached to the positively charged carbon atom?

A

the more stable the carbocation is

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15
Q

Order the stability of a secondary carbocation, tertiary carbocation and primary carbocation?

A

tertiary
secondary
primary

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16
Q

What will the product from an asymmetrical alkene tend to come from?

A

the more stable carbocation

17
Q

How fast do alkenes react with chlorine, bromine or iodine?

A

rapidly

18
Q

What is produced when alkenes react with chlorine, bromine or iodine?

A

dihalogenoalkanes

19
Q

How does a halogen add to the alkene?

A

across the double bond

20
Q

What does the halogen act as when a halogen and alkene react?

A

electrophile

21
Q

What are the two steps for when an alkene and halogen add?

A

formation of carbocation by electrophilic addition

rapid reaction with negative ion

22
Q

What is the bromine water test?

A

when a few drops of bromine water (reddish-brown) is added to an alkene, solution decolourised

23
Q

When bromine water is added to an alkene, why is the solution decolourised?

A

the products are colourless

24
Q

At what temperature does the reaction occur when concentrated sulphuric acid adds across the double bond of an alkene?

A

at room temperature

25
Q

Is it an exothermic or endothermic reaction when concentrated sulphuric acid adds across a double bond of an alkene?

A

exothermic

26
Q

What is the electrophile in a sulphuric acid molecule?

A

partially positive charged hydrogen atom

27
Q

What is formed when water is added to the product of the addition of concentrated sulphuric acid to an alkene?

A

an alcohol

28
Q

What is reformed when water is added to the product of the addition of concentrated sulphuric acid to an alkene?

A

sulphuric acid

29
Q

As sulphuric acid is reformed when water is added to the product of concentrated sulphuric acid and an alkene, what does the sulphuric acid act as?

A

catalyst

30
Q

How can you predict the products with an asymmetrical alkene?

A

by looking at the relative stability of the possible carbocations that could form

31
Q

Can water add across the double bond of alkenes?

A

yes

32
Q

How is the water being able to add across the double bond on alkenes used industrially?

A

to make alcohols

33
Q

At what conditions is water added across the double bond in alkenes to make alcohols? (4)

A

carries out with steam
suitable temperature
suitable pressure
acid catalyst i.e. phosphoric acid

34
Q

Equation for when water is added across the double bond of ethene?

A

CH2=CH2 (g) + H20 (g) = CH3CH2OH (g)

C14- ALKENES (3 decks)

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