Carbonyl compounds Flashcards
What is the functional group for carbonyl compounds?
C=O
Describe the bonding of the C=O bond.
*Refer to carbonyl compounds notes.
Describe the difference between an aldehyde and a ketone (2 points).
- Aldehyde: the carbon atom of the carbonyl group is attached to one or two hydrogen atoms at the end of the chain.
- Ketone: the carbonyl functional group is attached to two carbon atoms in the carbon chain. C=O in the middle of the carbon chain.
What type of reaction forms aldehydes from primary alcohols?
Oxidation (partial).
What are the reagents and conditions to form aldehydes from primary alcohols?
Potassium dichromate; K2Cr2O7(aq).
Concentrated H2SO4(aq)
Distillation.
Explain why distillation is used when forming aldehydres from primary alcohols.
- Provides energy for the reaction.
- To remove the product from the oxidising mixture to prevent further oxidation.
- The aldehyde can be separated from the reaction mixture as it has a lower boiling point.
Write an equation for the formation of propanal using propan-1-ol and potassium dichromate as the reagents.
CH3CH2CH2OH + [O] …. CH3CH2CHO + H2O
What type of reaction forms carboxylic acids from aldehydes?
Oxidation.
What are the reagents and conditions used when forming a carboxylic acid from an aldehyde?
Potassium dichromate; K2Cr2O7(aq) and concentrated H2SO4(aq).
Reflux.
Write an equation, using structural formula, for the reaction between propanal and potassium dichromate. Name the product.
CH3CH2CHO + [O] …. CH3CH2COOH
Propanoic acid.
What type of reaction forms ketones from secondary alcohols?
Oxidation.
What are the reagents and conditions for the reaction that forms ketones from secondary alcohols?
Potassium dichromate; K2Cr2O7(aq)
Concentrated H2SO4(aq)
Reflux
Write an equation, using structural formula, for the reaction between propan-2-ol and potassium dichromate. Name the product formed.
CH3C(OH)HCH3 + [O] …. CH3COCH3 + H2O
Propanone
State and explain, including ionic half equations, the observations that would be made in oxidation reactions when using K2Cr2O7(aq) (5 points).
- Cr2O7^2- + 14H+ + 6e- …. 2Cr^3+ + 7H2O
- Orange –> green.
- Cr2O7^2- …. Cr^3+
- Dichromate (IV) ions into Chromium (III) ions.
- If the alcohol is oxidised, the orange solution containing the dichromate (IV) ions is reduced to green solution containing chromium (III) ions.
What type of reaction do alkenes undergo?
Electrophilic addition.
Describe how the double bond in a carbonyl compound differs from that of an alkene?
- The double bond in an alkene is non-polar, the double bond in a carbonyl compound is polar.
- This is because oxygen is more electronegative than carbon.
Due to its dipole, what species does the C of the C=O bond attract?
Nucleophiles- electron pair donors.
What type of reactions do carbonyls undergo?
Nucleophilic addition reactions.
What kind of reaction changes aldehydes into primary alcohols and ketones into secondary alcohols?
Reduction reactions.
What are the reagents and conditions for the reaction to change from a ketone to a secondary alcohol?
NaBH4- sodium borohydride (a source of H- ions). Warm in aqueous solution.
*Write a general equation for the reaction of a general ketone with NaBH4.
*Refer to carbonyl compounds notes.
FOR EACH CARBONYL THAT’S REDUCED; 2[H]!!
*Describe the mechanism for the reduction of methanal into methanol.
*Refer to carbonyl compounds notes.
Why is HCN made in situ? (2 points)
- HCN is an extremely poisonous volatile liquid (bpt is 26 degrees).
- Making it in situ improves safety and increases reaction rate.
What are the reagents used to make HCN in situ?
NaCN and H2SO4(aq).
