Reactions

Question 1

What is the main reaction that alkenes undergo?

Answer 1

Addition reactions

Question 2

What is the addition reaction of alkenes more often called?

Answer 2

Halogenation

Question 3

Give two examples of halogens that alkenes react readily with during halogenation.

Answer 3

Cl2

Br2

Question 4

What is formed from the halogenation of an alkene?

Answer 4

A halo-alkane

e.g. 2,3-dichlorobutane

Question 5

What is needed for halogenation?

Answer 5

An alkene
A halogen molecule
No light or heat is necessary - reaction occurs on its own

Question 6

How does the halogenation of alkanes differ from the halogenation of alkenes?

Answer 6

Alkanes require light or heat to become halogenated

Question 7

What reaction prepares alkynes?

Answer 7

Elimination reactions

Question 8

How are alkynes prepared by an elimination reaction?

3

Answer 8

A strong base removes the hydrogens and halogens from either vicinal or germinal dihalides

This forms an alkyne

Done through two successive elimination reactions

Question 9

How can alkenes be made into alkynes?

3

Answer 9

Two step process

Halogenation of the alkene

Double dehydrohalogenation of the resulting vicinal dihalide

Question 10

From what two families can alcohols be formed?

Answer 10

Alkenes or alkyl halides

Question 11

How can alcohols be formed from alkenes?

5

Answer 11

Addition reaction of a water molecule to an alkene in the presence of an acid

Acid donates a hydrogen to break the double bond

Water bonds to molecule

Deprotonation then occurs

OH of water forms the hydroxyl group

Question 12

How can alcohols be formed from alkyl halides?

3

Answer 12

By the loss of a leaving group (halogen)

Water molecule then binds to molecule

Deprotonation then occurs to rid the H2O of one H leaving an OH group

Question 13

How are ethers synthesised?

Answer 13

A substitution reaction by reacting alkyl halides with an alkoxide ion

Question 14

What is an alkoxide ion?

Answer 14

Conjugate base of alcohol

i.e. alcohol without a H

Question 15

What is the synthesis of ethers called?

Answer 15

The Williamson Ether synthesis

Question 16

Give an example of an alkoxide ion used in ether synthesis/

Answer 16

sodium alkoxide

Question 17

How does the synthesis of ethers work?

3

Answer 17

Sodium alkoxide reacts with an alkyl halide containing chlorine

Alkoxide acts as a neutrophil
Alkyl halide acts as an electrophile

Form an ether and NaCl

Question 18

What happens when you oxidise a primary alcoho using a weak oxidantl?

Answer 18

It forms and aldehyde

Question 19

When happens when you oxidise a primary alcohol with a strong oxidant?

Answer 19

Forms and aldehyde then a carboxylic acid

Question 20

What is formed when you oxidise a secondary alcohol?

Answer 20

It forms a ketone

Question 21

Whats formed when you reduce an aldehyde?

Answer 21

It forms a primary alcohol

Question 22

What happens when you reduce a carboxylic acid?

Answer 22

It forms an aldehyde

Question 23

Whats formed when you reduce a ketone?

Answer 23

Secondary alcohol

Question 24

Define a substitution reaction

Answer 24

A substitution reaction is a chemical reaction during which one functional group in a chemical compound is replaced by another functional group

Question 25

Define an elimination reaction

Answer 25

An elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one- or two-step mechanism