Reactions
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What is the main reaction that alkenes undergo?
Addition reactions
What is the addition reaction of alkenes more often called?
Halogenation
Give two examples of halogens that alkenes react readily with during halogenation.
Cl2 Br2
What is formed from the halogenation of an alkene?
A halo-alkane e.g. 2,3-dichlorobutane
What is needed for halogenation?
An alkene A halogen molecule No light or heat is necessary - reaction occurs on its own
How does the halogenation of alkanes differ from the halogenation of alkenes?
Alkanes require light or heat to become halogenated
What reaction prepares alkynes?
Elimination reactions
How are alkynes prepared by an elimination reaction? 3
A strong base removes the hydrogens and halogens from either vicinal or germinal dihalides This forms an alkyne Done through two successive elimination reactions
How can alkenes be made into alkynes? 3
Two step process Halogenation of the alkene Double dehydrohalogenation of the resulting vicinal dihalide
From what two families can alcohols be formed?
Alkenes or alkyl halides
How can alcohols be formed from alkenes? 5
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
How can alcohols be formed from alkyl halides? 3
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
How are ethers synthesised?
A substitution reaction by reacting alkyl halides with an alkoxide ion
What is an alkoxide ion?
Conjugate base of alcohol i.e. alcohol without a H
What is the synthesis of ethers called?
The Williamson Ether synthesis
Give an example of an alkoxide ion used in ether synthesis/
sodium alkoxide
How does the synthesis of ethers work? 3
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
What happens when you oxidise a primary alcoho using a weak oxidantl?
It forms and aldehyde
When happens when you oxidise a primary alcohol with a strong oxidant?
Forms and aldehyde then a carboxylic acid
What is formed when you oxidise a secondary alcohol?
It forms a ketone
Whats formed when you reduce an aldehyde?
It forms a primary alcohol
What happens when you reduce a carboxylic acid?
It forms an aldehyde
Whats formed when you reduce a ketone?
Secondary alcohol
Define a substitution reaction
A substitution reaction is a chemical reaction during which one functional group in a chemical compound is replaced by another functional group