Aldehydes and ketones
Made using OCR Chemistry textbook. Pages 20- 27. Gent and Richie.
- Created by: Former Member
- Created on: 27-12-12 17:01
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- Aldehydes and ketones
- Functional group: C=O bond
- comprises of sigma and pi- bond
- pi bond= overlap of p orbitals on O and C atoms.
- O atom is more electronegative = dipole in C=O bond as e- more attracted to O
- Functional group= part of organic molecule thats responsible for its chemical reactions
- comprises of sigma and pi- bond
- Naming
- Aldehydes: end in -al
- Ketones: end in -one
- Parent chain= longest chain containing C=O. Numbered so smallest number is used.
- Aromatic aldehydes and ketones
- Compounds containing both a benzene ring and a carbonyl group
- Benzaldehyde (almond)
- Phenylethanone
- Compounds containing both a benzene ring and a carbonyl group
- Oxidation
- Oxidising mixture of potassium dichromate and sulphuric acid
- Orange to green
- Primary alcohol to aldehyde, secondary to ketone
- Ketone cannot be oxidised further
- Aldehyde oxidised to a carboxylic acid
- Oxidising mixture of potassium dichromate and sulphuric acid
- Reduction
- Reverses oxidation, i.e. aldehyde back to primary alcohol etc.
- Testing
- 1. Detecting presence of carbonyl group
- Use Brady's reagent (solution of 2,4-DNPH)
- Orange precipitate forms
- Only +ve for aldehydes & ketones
- 3. Identify
- Precipitate: filter, purify, recrystallise, measure m.p., compare to known values.
- Orange precipitate forms
- Use Brady's reagent (solution of 2,4-DNPH)
- 1. Detecting presence of carbonyl group
- Functional group: C=O bond
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