Presentation on theme: "Carbonyl chemistry -Production of carbonyl compounds"— Presentation transcript:
1Carbonyl chemistry -Production of carbonyl compounds -Oxidation and Reduction reactions-Further oxidation reactions.
2Formation of carbonyl compounds Starting with an alcohol, react with an oxidising agent (such as acidified potassium dichromate)Propan-1-ol + [O] Propanal +water
3The carbonyl functional group PLANAR WITH BOND ANGLES OF 120°ORBITAL OVERLAPNEW ORBITALThe bond is polar due to the difference in electronegativity.
4Aldehydes vs. KetonesAldehydes have the carbonyl group at the end of a carbon chain (joined to only one carbon)Ketones have the carbonyl group bonded to two carbons.C = OHC = OHCH3C = OCH3C = OC2H5CH3
6Identification of carbonyls IR spectroscopy shows a strong peak around cm-1
7Oxidation of carbonylReacting an aldehyde with an oxidising agent (acidified dichromate ions) produces a carboxylic acid.Propanal + [O] Propanoic acid +water
8Reduction of carbonyls Carbonyl groups can also be reduced.Reduction agent used is Sodium tetrahydroborate(III) (also called Sodium Borohydride)This is classed as a weak reducing agent.
9Reduction of carbonyls Propanal is reduced to a primary alcohol by sodium borohydride.Propanal + 2[H] Propan-1-ol
10Reduction continued NaBH4 reacts with ketones also. Propanone + 2[H] propan-2-ol
11Reduction explainedThe BH4 ion is acting as a source of hydride ions (:H-)Hydride ions being a negatively charged hydrogen ion containing a lone pair of electronsThe mechanism is an example of nucleophilic addition.H- ion is attracted to the δ+C of the carbonyl, forming a new C-H bondThe resulting O- ion forms a dative covalent bond using the H+ from a water molecule
13Carbonyl questions Write equations + mechanisms for the reduction of: Butanal2-methylhexan-3-oneDefine the term nucleophileShow the mechanism for the reaction between butanone and NaBH4
14Carbonyl chemistry 2 chemical tests on carbonyls -How to detect a carbonyl group-Aldehyde or ketone?
15ILPAC experiment 8.4Using the instruction sheets, follow the method for experiment 8.4 A and 8.4 BDO NOT DO EXPERIMENT CMake full and detailed notes on what you observe during the reactions.
16Condensation reactions We can detect the presence of a carbonyl group using 2,4-dinitrophenylhydrazine (abbreviated to 2,4-DNP or 2,4-DNPH).2,4-DNPH is alsocalled Brady’s reagent whenprepared with methanol andsulfuric acid.
17Using 2,4-DNPHWhen Brady’s reagent is added to an aldehyde or ketone, a yellow or orange precipitate is formed.The precipitate, called a 2,4-dinitrophenylhydrazone derivative confirms the presence of a carbonyl functional group.
18Aldehyde or ketoneAldehydes and ketones can be distinguished from each other by using Tollen’s reagentTollen’s reagent is a weak oxidising agent, the carbonyl group is oxidised to form a carboxylic acid.Ammoniacal silver nitrate
19Tollen’s reagent. Silver ions are reduced to silver metal Ag+(aq) + e- Ag(s)Aldehyde + [O] Carboxylic acid
20Carbonyl questions 2The carbonyl compounds CH3COCH3 and CH3CH2CHO are structural isomers.Name these compoundsState the reagents used and observations made to prove the presence of a carbonyl group in these compoundsState the reagents and observations made to distinguish between the two chemicals.
21Carbonyl chemistry 3 Identifying a carbonyl compound -Determining experimentally an unknown carbonyl compound
22ILPAC 8.5Using the instruction sheets given last lesson, carry out experiment 8.5, parts A and BComplete a detailed method for identifying a carbonyl compoundPurifying by recrystallisation -> melting point determination -> compare melting point to known values.
23Carbonyl questions 3Explain how you would use the solid obtained from the reaction of an aldehyde with 2,4-DNPH to prove the original aldehyde was butanal.The reaction of 2,4-DNPH with ethanal gives water as a product. Suggest the type of reaction taking place.