Alkenes And alcohols Flashcards Preview

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Flashcards in Alkenes And alcohols Deck (23)
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1
Q

What are alkenes made of?

A

Carbon and hydrogen so hydrocarbons

2
Q

Do alkenes have the same number of H’s as each other?

A

No alkenes with more than one double bond have fewer H’s than the General formula suggests

3
Q

What do alkenes molecules have?

A

At least one C=C double covalent bond

4
Q

Why are alkenes unsaturated?

A

Because they make more bonds with extra atoms in addition reactions

5
Q

Why are alkenes pretty reactive?

A

There are two pairs of electrons in the C=C double bond so has a really high electron density

6
Q

Electrophilic addition in alkenes?

A

Double bond open up and atoms are added to the carbon atoms
Electrophiles addition reactions happen because the double bond has got plenty of electrons and is easily attacked by electrophiles

7
Q

What are electrophiles?

A

Electron-pair acceptors
Usually short of electron so attracted to areas where there are lots of them
Positively charged ions: H+, NO2+
Polar molecular the delta + is attached to places with lots of electrons

8
Q

Alkenes General formula

A

CnH2n

9
Q

How do you test for unsaturation?

A

Use bromine water

10
Q

Description of what happens to make bromine water work?

A

When you shake an alkene with orange bromine water the solution quickly decolourises goes from orange to colourless. Bromine across C=C double bond to form colourless dibromoalkane
Happens by electrophiles addition

11
Q

What do you need to do about bromine water mechanism?

A

Have you learnt it? If not learn it and give this a red.

12
Q

Carbocation is?

A

an organic ion containing a positively charged carbon atom

13
Q

What else do alkenes undergo addition with?

A

Hydrogen halides to form halogenoalkanes

It forms Bromo…(alkane name)

14
Q

What if a hydrogen halide is added to an unsymmetrical alkene?

A

Two possible products

15
Q

What determines how much of the product is formed?

A

Depends on how stable the carbocation formed in the middle of the reaction is (carbocation intermediate)
Carbocations with more alkyl groups are more stable because alkyl groups feed electron towards the positive end. More stable carbocation is more likely to form.

16
Q

Least stable to most stable?

A

Primary carbocation one R group
Secondary carbocation
Two R groups
Tertiary carbocation three R groups

17
Q

Mechanism behind hydrogen bromide please learn this.

A

Have done

18
Q

Mechanism of electrophilic addition H2SO4

A

Cold concentrated sulfuric acid reacts with alkene in electrophilic addition
If you add cold water and warm product it hydrolyses to form an alcohol
Sulfuric acid isn’t used up (catalyst)

19
Q

Overall equation for producing ethanol

A

H2C=CH2+H2O -H2SO4->C2H5OH

20
Q

What happens if you do this with unsymmetrical alkenes?

A

Mixture of products

Most stable carbocation intermediate will be the major product

21
Q

Alcohol homologous series?

A

Hydroxyl group

-OH

22
Q

What is an alcohol?

A

Primary (1 R group)
Secondary (2 R group)
Tertiary (3 R group)

23
Q

How can you make alkenes from alcohol?

A

By eliminating water in a dehydration reaction.

CnH2n+OH=>CnH2n+H2O