Azo compounds with arene groups are more stable than those with alkyl groups. Why?
The N=N group is stabilised by becoming part of an extended delocalised system involving the arene groups
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Azo compounds are formed as a result of a ________ reaction between a _________ ____ and a ________ ______
Coupling reaction, diazonium salt, coupling agent
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Why are diazonium salts unstable?
They tend to lose the N+=N group as N2(g)
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Why are diazonium salts prepared in ice-cold solution and used immediately?
They decompose above about 5 degrees Celsius in aqueous solution (the solid is explosive)
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How are diazonium salts prepared?
Diazotisation: Adding a cold solution of sodium nitrite (NaNO2) to a solution of an arylamine in dilute acid (usually HCl or H2SO4) below 5 degrees Celsius. The acid reacts with NaNO2 producing nitrous acid which then reacts with the arylamine
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What happens in a general diazo coupling reaction?
A diazonium salt reacts with another compound containing a benzene ring (this is the coupling agent). The diazonium ion acts as an electrophile and reacts with the benzene ring of the coupling agent
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What is seen when a solution of benzenediazonium salt is added to an alkaline solution of phenol?
A yellow-orange azo compound is formed
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What is seen when a solution of benzenediazonium salt is added to an alkaline solution of naphthalen-2-ol?
A red azo compound is formed
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What is seen when a solution of benzenediazonium salt is added to a solution of phenylamine?
A yellow azo compound is formed
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Azo compounds are stable compounds. How does this affect their colours?
Their colours do not fade
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Other cards in this set
Card 2
Front
Azo compounds with arene groups are more stable than those with alkyl groups. Why?
Back
The N=N group is stabilised by becoming part of an extended delocalised system involving the arene groups
Card 3
Front
Azo compounds are formed as a result of a ________ reaction between a _________ ____ and a ________ ______
Back
Card 4
Front
Why are diazonium salts unstable?
Back
Card 5
Front
Why are diazonium salts prepared in ice-cold solution and used immediately?
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