Alkene and alkyne synthesis Flashcards
What are the two methods that alkynes can be synthesised?
Nucleophilic substitution and elimination.
Write an equation for the formation of an alkyne via nucleophilic substitution.
Ph-=-H —->(strong base) Ph-=- - —-> (ph^-br, sn2) ph/\/=-ph
Is the elimination to form alkynes e1 or 2?
2.
What are the methods in which alkenes can be synthesised?
Elimination chemistry, reduction chemistry and Wittig chemistry.
Write the mechanisms for the elimination of an alkane to form an alkene.
read ur booklet lol
What are the three reduction methods to form alkenes?
Pd/C, Lindlar and dissolving metal reduction.
What is the problem with the Pd/C reduction method?
It is impossible to stop the process at the alkene stage. An alkane will be formed.
How do the hydrogens add in the Lindlar and Pd/C reaction?
In a syn fashion - forms a Z-alkene.
How does the Lindlar reduction method differ from Pd/C?
Lindlar is a poisoned palladium species - it is not active enough to make an alkane so the process is stopped when the alkene forms.
What is the dissolving metal reduction method and what type of alkene does it form?
Sodium metal dissolved in liquid ammonia leads to electron loss and generates Na+ ions to initiate a radical mechanism. It forms an E alkene.
What is the Wittig method to form an alkene?
A carbonyl group is converted to an alkene using phosphorane.
Does Wittig favour an E or Z alkene?
It depends on the conditions of the reaction.
