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37 Cards in this Set
- Front
- Back
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What do aldehydes and ketones both have in common?
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They contain the carbonyl functional group, C=O.
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What is a functional group?
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The part of an organic molecule responsible for its reactions.
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What does the double bond in the carbonyl and alkene function groups comprise of?
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A sigma-bond and a pi-bond.
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Why doesn't he carbonyl bond react in the same way as the double bond in alkene?
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Because the oxygen atom is more electronegative than the carbon atom. This creates a dipole in the C=O bond because bonded electrons are attracted towards the oxygen.
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When is an aromatic aldehyde or ketone?
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Compounds containing both a benzene ring and a carbonyl group.
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What is the simplest aromatic aldehyde?
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Benzaldehyde.
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What is the simplest aromatic ketone?
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Phenylethanone.
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What colour and what scent is benzaldehyde at rtp?
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A colourless liquid with almond-like odours.
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What fragrances does phenylethanone create?
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Cherry, honeysuckle, jasmine and strawberry.
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Which aromatic aldehyde makes up 80-90% of cinnamon bark?
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Cinnamaldehyde.
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Which oxidising agent is used to oxidise primary and secondary alcohols?
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K2Cr2O7 and H2SO4. (Acidified potassium dichromate).
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How do you prevent a primary alcohol from further oxidising to a carboxylic acid after being oxidised to an aldehyde?
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By distilling the aldehyde as it is formed.
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Which reducing agent is used to reduce carbonyl compounds to alcohols?
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Sodium borohydride, NaBH4. (Water as solvent).
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What type of reaction is aldehydes and ketones reacting with NaBH4.
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Nucleophilic addition.
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What is the nucleophile in the reaction between NaBH4 and aldehydes and ketones?
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The hydride ion... :H-
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What is a nucleophile?
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An atom or group of atoms attached to an electron-deficient centre, where it donates a pair of electrons to form a new covalent bond.
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What does a curly arrow show in reaction mechanisms?
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A symbol used to show the movement of an electron pair in the breaking or formation of a covalent bond.
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What reagent can you use to detect aldehydes or ketones?
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2,4-dinitrophenylhydrazine.
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What is Brady's reagent?
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2,4-DNP in a mixture of methanol and sulphuric acid.
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What happens when an aldehyde or a ketone is added to 2,4-DNP (Brady's reagent)?
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A yellow or orange precipitate is formed.
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Is Tollens' reagent a weak or strong oxidisng agent?
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Weak
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What are aldehydes easily oxidised to?
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Carboxylic acids.
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How is Tollens' reagent made?
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> Aqueous NaOH is added to aqueous AgNO3 until a brown ppt. of silver oxide is formed
> Dilute aqueous NH3 is then added until the precipitate just dissolves |
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What is the other name for Tollens' reagent?
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Ammoniacal silver nitrate.
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What's the ionic equation for silver when Tollens' reagent oxidises an aldehyde?
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Ag+(aq) + e- ----> Ag(s)
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How can you further identify an aldehyde or a ketone after all test tube tests have been carried out?
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> Use yellow/orange solid 2,4-DNP derivative
> The impure product is filtered and recrystallised to produce purified sample of yellow/orange crystals, filer and allow to dry > Melting point is then measured and recorded > Compare melting point to a database to identify original aldehyde or ketone |
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Why are carboxylic acids with more than four carbon atoms not so soluble in water?
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Due to the long non-polar hydrocarbon chain, which doesn't interact with water molecules.
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Are carboxylic acids weak or strong?
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Weak
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What are the products from carboxylic acid and a reactive metal?
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A salt and hydrogen gas.
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What are the products from carboxylic acids and aqueous bases, such as metal hydroxides?
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A salt and water.
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What are the products from carboxylic acids and carbonates?
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A salt, water and carbon dioxide.
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How is an ester formed?
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By reacting a carboxylic acid with an alcohol in the presence of an acid catalyst, often conc. sulphuric acid.
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Why is making an ester from an acid anhydride better than from a carboxylic acid?
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Gives a much better yield.
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What is hydrolysis?
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The chemical breakdown of a compound by reaction with water.
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What is the role of acid in acid hydrolysis of esters?
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It acts as a catalyst, with water breaking the ester down.
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What is the alkaline hydrolysis of esters sometimes called?
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Saponification.
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Name some uses of esters.
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Flavouring in food, as perfumes.
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