Flashcards
Aldehydes and Ketone
Cards in this deck (19)
- 1General FormulaCnH2nO
- 2Reactivity# Rate nucleophillic addition to carbonyl group-increases with size of +ve charge on carbon atom
# Groups that release electron density towards C decreasing value of charge - 3Methanal > Aldehyde > Ketone# Aldehyde - carbonyl group - H atom attatched
# Ketone - carbonyl group - 2 hydrocarbon atoms attached - 4Boiling Points# Methanal - gas - (-21 C)
# Ethanal - boils close to room temp
# Other - rises as molecules get bigger
# Size of BP depends on strength of intermolecular forces - 5VDW# Get stronger as molecules get longer
# More electrons-increased strength of temporary dipoles - 6Dipole-Dipole Interactions# Polar molecules
# due to C=O
# Interactions between permanent dipoles on nearby molecules - 7ALdehydes and ketones are highly polar# Don't have H atoms attached directly to oxygen
# No H bonds - 8Solubility# Shorter chains-mix completely
# H bonds form between water and the O of C=O
# As chain length increases become less soluble - 9H bond with H2O# Slightly +ve H attracted to lone pair of O
# VDW and DIpole with water
# Releases energy
# Chain length increases-hydrocarbon tails get in way - 10Preparation of Aldehydes Equation1 Alcohol -> Aldehyde -> Carboxylic
- 11Preparation of aldehydes# OH group attached to carbon bearing 2 H atoms
# Oxidation removes H and OH to form aldehyde
# H can be removed by oxidant to form Carboxylic acid - 12Why is aldehyde distilled off?Stop it being reduced further to a carboxylic acid
- 13Aldehyde refluxedAllows for full oxidation to a carboxylic acid
- 14Oxidising agentAcidified potassium dichromate
Orange -> Green
Acidified Potassium permanganate
Purple -> colourless - 15Preparation of Ketones Equation2 Alcohol -> Ketone
- 16Preparation of ketones# OH group attached to C bearing H atom
# Oxidising agent removes H and OH
# No further oxidation - 17Reduction# Reduced to corresponding 1 or 2 alcohol
- 18Lithal - Lithium Aluminium hydride LiAlH4# Contains hydride ion
# Acts as nucleophile
# Attacks C=O in nucleophillic addition - 19Lithal - Safety# Powerful reactant
# Reacts vigorously + violently with water
# Only used in anhydrous conditions
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- A level Chemistry (Aldehydes and Ketones) Flashcards on Aldehydes and Ketone, created by Jemma Catlin on 01/12/2018.
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- Jemma Catlin
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