What's formed when 2,4-DNPH is added to an aldehyde/ketone?
Respuesta
A blue solid
An orange/yellow precipiate
An orange/yellow solution
A green precipitate
Pregunta 4
Pregunta
What does the 2,4-DNPH derivative confirm?
Respuesta
The presence of C=O
The presence of COOH
The presence of OH
The presence of COO
Pregunta 5
Pregunta
What happens when 2,4-DNPH added to carboxylic acid/ester?
Respuesta
An orange/yellow precipitate formed
An orange to green colour change
A solid disappears
No precipitate formed
Pregunta 6
Pregunta
What is Tollen's reagent?
Respuesta
A weak oxidising agent
A weak reducing agent
A strong oxidising agent
A strong reducing agent
Pregunta 7
Pregunta
What happens to aldehydes when Tollens' reagent is added to it?
Respuesta
Oxidised to ketones
Reduced to carboxylic acids
Oxidised to carboxylic acids
Reduced to alcohols
Pregunta 8
Pregunta
What observation do you see when Tollen's reagent is added to an aldehyde?
Respuesta
Brown precipitate
Silver mirror
No observation
Brick red precipitate
Pregunta 9
Pregunta
Why is a silver mirror formed?
Respuesta
Al ions oxidised to Al metal
Silver ions reduced to silver metal
Silver ions oxidised to silver metal
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)
Ag+(aq) ---> Ag(s) + e-
Ag+(s) + e- ---> Ag(aq)
Ag+(aq) + e- ---> Ag(s)
Pregunta 11
Pregunta
What observation do you see when Tollen's added to ketone?
Respuesta
No observation
Silver mirror
Deep blue solution
Orange to green colour change
Pregunta 12
Pregunta
What's the reason for no observation?
Respuesta
The reaction is too slow
Ketones are not reduced by Tollens' reagent
Ketones are not oxidised by Tollens' reagent
Ketones are just dead
Pregunta 13
Pregunta
What's the oxidising species in Tollens' reagent?
Respuesta
Ag(aq)
Br+(aq)
Ag(s)
Ag+(aq)
Pregunta 14
Pregunta
What conditions are required for these reactions?
Respuesta
Warm
Reflux
conc H2SO4
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
melting point
high
database
data table
original
Pregunta 16
Pregunta
Why does the yellow/orange solid have to be recrystallised?
Respuesta
Because it needs to be crystallised again
Because its slightly impure
Because it's fun
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