Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
29 Cards in this Set
- Front
- Back
- 3rd side (hint)
|
define aldehyde
|
organic compound containing a C=O bond at the end of its chain
|
carbon-oxygen double bond placement similar to those of common alcohols
|
|
|
define ketone
|
organic compound containing a C=O bond in the middle of its chain/anywhere but the first and last carbon
|
|
|
|
What oxidising agent is used to oxidise alcohols
|
mixture of concentrated sulfuric acid (H2SO4) and potassium dichromate (K2Cr2O7)
|
|
|
|
What can a primary alcohol be oxidised to
|
aldehyde then carboxylic acid
|
|
|
|
How do you obtain an aldehyde when oxidising a primary alcohol
|
By heating and distilling the aldehude immediately as it's formed, stopping the oxidation
|
|
|
|
How do you obtain a carboxylic acid when oxidising a primary alcohol
|
by refluxing with an excess of the oxidising agent, stopping further oxidation to take place
|
|
|
|
Name two reducing agents for aldehydes and ketones
|
sodium tetrahydridoborate, NaBH4, ina water and lithium tetrahydridoaluminate, LiAlH4, in ether
|
|
|
|
What is a tertiary alcohol oxidised to?
|
tertiary alcohols can't be oxidised
|
|
|
|
Is the carbonyl group, C=O, in aldehydes in carbonyl compoinds polarised? Why / why not?
If yes, what are the charges |
Yes it is polarised, because the oxygen has a much higher electronegativity than carbon, so the electrons are more attracted towards thr oxygen atom.
The oxygen is slightly negatively charged and the carbon is slightly poaitively charged |
|
|
|
What is a carbonyl compound?
|
C=O bond
|
|
|
|
What groups are attached to the carbonyl atom in aldehydes?
|
One hydrogen atom and a hydrocarbon group / two hydrogen atoms (less common)
|
|
|
|
What groups are attached to the carbonyl carbon atom in keyones?
|
Two hydrocarbon atoms
|
|
|
|
How can you produce aldehydes?
|
Oxidising a primary alcohol with an oxidising agent like concentrated sulfuric acid,H2SO4 and potassium dichromate, K2CrO7.
Heat and distill immediately once aldehyde formed. |
|
|
|
How do you produce a ketone
|
Oxidising a secondary alcohol with an oxidising agent like concentrated sulfuric acid, H2SO4, and potassoum dichromate, K2Cr2O7.
|
|
|
|
What reaction mechanism can occur with carbonyl compound and why?
|
Nucleophillic addition because the polar C=O is electron-deficient so it atttacts nucleophiles, allowing addition reactions to take plave across that bond
|
|
|
|
What mechanism happens when aldehydes/ketones?
|
Nucleophillic addition
|
|
|
|
Describe the three stages in the reaction of aldrhydes/ketones with HCN
|
CN donates a lone pair to the slightly positive carbonyl carbon atom. An electron pair from the C=O bond goes to the slightly negatove vahrged Oxygen atom, forming a C-C bond
The lone pair in the oxygen goes to a H± atom, forming a O-H bond. hydroxynitrile formed |
|
|
|
What IM forces are in aldehydes and ketones
|
VDW forces and permanent dipole-dipole imteractions.
|
|
|
|
How does chain length affect solubility of aldehydes and ketones? Why
|
longer chain, less soluble because hydrocarbon prevent attractions from occurring.
|
|
|
|
Wjy are aldehydes and ketones soluble
|
Because they can form hydrogen bonds with wayer molecules.
slightly positive H in water with a lone pair on the oxygrn atom of a carbonyl group. |
|
|
|
How can diapersion forces and dipole-dipole attractions help the solubility
|
When these attractions are formed, they release energy, which can help to separate the water molecules and the aldehyde/ketone molecules from.each other, so they can mix together.
|
|
|
|
How can you identify a carbonyl group?
|
brady's agent 2,4-DNP - red orange solid
|
|
|
|
What reaction takes place when aldehydes/ketones react with Brady's reagent?
|
Condensation which ia addition followed by water elimimation
|
|
|
|
What observation is there with Brady's reagent
|
yellow/orange crystalline solids
|
|
|
|
Why is Brady's reagent used?
What technologocal method is a more practical alternative |
less soluble so crystallise easier
Infrared spectroscopy |
|
|
|
Why can aldehydes be oxidised and ketones can't
|
because the carbonyl carbon atom in aldehydes also have a hydrogen atom attached to it while ketones don't
|
|
|
|
how do oxidation states change for the tests for aldehydes and ketones
|
reagents get reduced, aldehyde gets oxidised to carboxylic acid
|
|
|
|
why is there a colour change for aldehyde tests
|
because the aldehyde reduces the reagents
|
|
|
|
What is a tollen's reagent
|
solution of silver nitrate in aqueous ammonia
|
|
