4852752
Pregunta 1
Pregunta
How do you identify a carbonyl compound?
Respuesta
-
Add Tollens' reagent
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Add Biuret reagent
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Add 2,4-DNPH
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Add carboxylic acid
Pregunta 2
Pregunta
What is Brady's reagent?
Respuesta
-
A mixture of H2SO4 and benzene + 2,4-DNPH
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A mixture of HCl and ethanol + 2,4-DNPH
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A mixture of NaOH and methanol + 2,4-DNPH
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A mixture of H2SO4 and methanol + 2,4-DNPH
Pregunta 3
Pregunta
What's formed when 2,4-DNPH is added to an aldehyde/ketone?
Respuesta
-
A blue solid
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An orange/yellow precipiate
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An orange/yellow solution
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A green precipitate
Pregunta 4
Pregunta
What does the 2,4-DNPH derivative confirm?
Respuesta
-
The presence of C=O
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The presence of COOH
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The presence of OH
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The presence of COO
Pregunta 5
Pregunta
What happens when 2,4-DNPH added to carboxylic acid/ester?
Respuesta
-
An orange/yellow precipitate formed
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An orange to green colour change
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A solid disappears
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No precipitate formed
Pregunta 6
Pregunta
What is Tollen's reagent?
Respuesta
-
A weak oxidising agent
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A weak reducing agent
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A strong oxidising agent
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A strong reducing agent
Pregunta 7
Pregunta
What happens to aldehydes when Tollens' reagent is added to it?
Respuesta
-
Oxidised to ketones
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Reduced to carboxylic acids
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Oxidised to carboxylic acids
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Reduced to alcohols
Pregunta 8
Pregunta
What observation do you see when Tollen's reagent is added to an aldehyde?
Respuesta
-
Brown precipitate
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Silver mirror
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No observation
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Brick red precipitate
Pregunta 9
Pregunta
Why is a silver mirror formed?
Respuesta
-
Al ions oxidised to Al metal
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Silver ions reduced to silver metal
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Silver ions oxidised to silver metal
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Al ions reduced to Al metal
Pregunta 10
Pregunta
What is the equation for the silver mirror being formed?
Respuesta
-
Ag-(aq) + e+ ---> Ag(s)
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Ag+(aq) ---> Ag(s) + e-
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Ag+(s) + e- ---> Ag(aq)
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Ag+(aq) + e- ---> Ag(s)
Pregunta 11
Pregunta
What observation do you see when Tollen's added to ketone?
Respuesta
-
No observation
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Silver mirror
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Deep blue solution
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Orange to green colour change
Pregunta 12
Pregunta
What's the reason for no observation?
Respuesta
-
The reaction is too slow
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Ketones are not reduced by Tollens' reagent
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Ketones are not oxidised by Tollens' reagent
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Ketones are just dead
Pregunta 13
Pregunta
What's the oxidising species in Tollens' reagent?
Respuesta
-
Ag(aq)
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Br+(aq)
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Ag(s)
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Ag+(aq)
Pregunta 14
Pregunta
What conditions are required for these reactions?
Respuesta
-
Warm
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Reflux
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conc H2SO4
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Alkaline
Pregunta 15
Pregunta
Filter and [blank_start]recrystallise[blank_end] product. Measure [blank_start]melting point[blank_end] of purified product which is very [blank_start]high[blank_end]. Compare the melting point to a [blank_start]database[blank_end] or [blank_start]data table[blank_end] to identify the unknown product and therefore the [blank_start]original[blank_end] carbonyl compound.
Respuesta
-
recrystallise
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melting point
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high
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database
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data table
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original
Pregunta 16
Pregunta
Why does the yellow/orange solid have to be recrystallised?
Respuesta
-
Because it needs to be crystallised again
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Because its slightly impure
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Because it's fun
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Because it needs to be more solid
Pregunta 17
Pregunta
Why can't boiling points be used to distinguish between aldehydes and ketones?
Respuesta
-
It's not possible to know all of the boiling points for every single one
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It will all boil away
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Some are very close together/similar
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It's not accurate enough
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