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© www.chemsheets.co.uk A2 1049 2-June-2016 ALDEHYDES methanal ethanal propanal 3-methylbutanal © www.chemsheets.co.uk A2 1049 2-June-2016 KETONES propanone butanone pentan-3-one 4-methylpentan-2-one © www.chemsheets.co.uk A2 1049 2-June-2016 OXIDATION & REDUCTION © www.chemsheets.co.uk A2 1049 2-June-2016 OXIDATION & REDUCTION • Tollen’s reagent, contains [Ag(NH3)2]+ • Used to test for aldehydes – gives silver mirror • Reduced from Ag(+1) to Ag(0) OXIDATION & REDUCTION • Fehling’s solution, contains Cu(+2) • Used to test for aldehydes – gives brick-red precipitate of Cu2O • Reduced from Cu(+2) to Cu(+1) OXIDATION & REDUCTION • Acidified potassium dichromate, contains Cr2O72• Used to test for alcohols (1y and 2y) & aldehydes – goes from orange Cr2O72- to green Cr3+ • Reduced from Cr(+6) to Cr(+3) OXIDATION & REDUCTION Distillation Reflux Aldehyde condenses back into reaction mixture and reacts further Alcohols and carboxylic acids (have hydrogen bonds between molecules) have higher bpts than aldehydes – so aldehyde can be distilled out as formed NUCLEOPHILIC ADDITION + – • Addition reactions: atoms add across C=O to the C and O • C is + so attacked by nucleophiles (electron pair donors) • The three atoms attached to the C are planar © www.chemsheets.co.uk A2 1049 2-June-2016 NUCLEOPHILIC ADDITION Reduction with NaBH4 + 2[H] H _ :H : _ © www.chemsheets.co.uk A2 1026 25-May-2016 NUCLEOPHILIC ADDITION e.g. ethanal + NaBH4 + 2[H] + 2[H] H _ _ :H H :H : _ : _ © www.chemsheets.co.uk A2 1026 25-May-2016 NUCLEOPHILIC ADDITION e.g. propanone + NaBH4 + 2[H] + 2[H] H _ H _ :H :H : _ : _ © www.chemsheets.co.uk A2 1026 25-May-2016 NUCLEOPHILIC ADDITION Reaction with KCN then acid + HCN H _ :CN : _ © www.chemsheets.co.uk A2 1026 25-May-2016 NUCLEOPHILIC ADDITION :CN :CN _ _ • many hydroxynitriles contain chiral C • formed as racemic mixture (50/50 mixture of enantiomers) • as equal chance of attack from above & below plane © www.chemsheets.co.uk A2 1026 25-May-2016 :CN :CN _ _ © www.chemsheets.co.uk A2 1026 25-May-2016 NUCLEOPHILIC ADDITION e.g. propanone + KCN then acid + HCN + HCN H _ H _ :CN :CN : _ : _ © www.chemsheets.co.uk A2 1026 25-May-2016 NUCLEOPHILIC ADDITION e.g. propanal + KCN then acid + HCN + HCN H _ H _ :CN :CN : _ : _ © www.chemsheets.co.uk A2 1026 25-May-2016
