Aldehyde And Ketone Flashcards
Prep of both ketone and aldehyde
1) By oxidation of alcohol-by primary aldehyde are prepared and by secondary ketone are prepared
2) By dehydration of alcohol- alcohol vapours are passed over heavy metal catalyst 1°- aldehyde 2°- ketone
3) By hydrocarbon-from ozonolysis Or from hydration of alkynes
Total method of prep of aldehyde
3
1) from acyl chloride (Rosenmund reduction)
2) From nitrile and ester (nitrile rexn is known as Stephen reaxn)
3) From hydrocarbon(includes etard)
Prep of aldehyde from acid chloride/acyl chloride/rosenmund reduction
Reagent-H2 Pd-BaSO4
Prep of aldehyde from nitrile by stephan reaxn
Reagent-SnCl2 and HCl then intermediate on hydrolysis give aldehyde
Intermediate-RCH=NH
Prep of aldehyde from nitrile and ester
Reagent-DIBAL-H
Imine then hydrolysis to give aldehyde
Prep of aldehyde from reduction of methyl benzene with use of chromyl chloride(CrO2Cl2) /etard reaxn
Reagent-CrO2Cl2 and CS2 to give chromium complex as intermediate and to give aldehyde as product after hydrolysis
Prep of aldehyde from chromium oxide (CrO3)
Reactant-Toluene Or substituted toluene
Reagent CrO3 and (CH3CO)2O acetic anhydride
Intermediate-Benzenediacetate
Then hydrolysis in presence of heat give benzaldehyde
Prep of aldehyde from side chain chlorination
Reactant-Toluene
Reagent-Cl2+hv
Intermediate-Benzal chloride
Hydrolysis at 373K to give benzaldehyde
Prep of aldehyde by gatterman koch rexn
Reactant-Aldehyde
Reagent-CO, HCl, Anhyd.AlCl3 Or CuCl
From what method aromatic aldehyde are prepared
From aromatic hydrocarbon by
1) oxidation of methyl benzene(includes etard)
2) side chain chlorination
3) gatterman koch
Commercial method of prep of benzaldehyde
By side chain chlorination followed by hydrolysis
Prep of ketone from acyl chloride
Treatment of acyl chloride with dialkylcadmium (R2Cd).
Acyl chloride+R2Cd gives ketone and CdCl2
Prep of dialkylcadmium
Reaction of cadmium chloride (CdCl2) with Gringnard reagent
Gringnard reagent+CdCl2 give R2Cd +Mg(X)Cl
Prep of dialkylcadmium
Reaction of cadmium chloride (CdCl2) with Gringnard reagent
Gringnard reagent+CdCl2 give R2Cd +Mg(X)Cl
Prep of ketone from nitrile
Reagent-Grignard reagent
Followed by hydrolysis
Prep of ketone from benzene or substituted benzenes/Friedel-Crafts acylation reaction
Benzene+Acid chloride in presence of anhydrous AlCl3 to give benzene substituted ketone
Reduction of hydrocarbon of ketone and aldehyde incudes
Clemmensen and wolff kishner reaxn
Clemmensen rexn
Reactant-Aldehyde and ketone
Reagent Zn-Hg and HCl
Product- CH2 group in place of C=O
+H2O
Wolff kishner reaxn
Reactant-Aldehyde and ketone
Reagent-Hydrazine(NH2NH2) followed by heating with sodium or Pottasium hydroxide in high boiling solvent such as etylene glycol
Product-remoce H2O and give CH2 in place of C=O with N2
Oxidation of aldehyde
Aldehyde easily oxidize to carboxylic acid with mild oxidizing agent
Oxidation of ketone
Oxidizes under vigorous conditions i.e strong oxidising agents and at elevated temp
C-C cleavage
Tests for differentiating aldehyde and ketone
1) tollens test
2) Fehling’s test
Tollens reagent
2[Ag(NH3)2]+ known as ammonical silver nitrate solution
Tollen’s test (only theory)
A bright silver mirror is produced due to the formation of silver mirror as a confirmation of aldehyde (which is due to formation of carboxylate ion)
This reaction occur in alkaline medium
Tollen’s test rexn
RCHO + tollen’s reagent-> RCOO- +2Ag +2H2O +4NH3
Fehling’s reagent
2 solution
Fehling solution A- aq.Copper sulphate
Fehling solution B- alkaline sodium Pottasium tartarate (Rochelle salt)
These solution are mixed in equal amount before test
Fehling’s test (only theory)
On heating aldehyde with fehling’s reagent gives a reddish brown precipitate
Aldehyde are oxidized to corresponding carboxylate anion
Aromatic aldehyde do not react to this test
Fehling’s test rexn
RCHO+2Cu+2 +5OH- –> RCOO- + Cu2O + 3H2O
Cu2O is red brown ppt know as cupprous oxide
Reason behind acidity of alpha H of carbonyl grp
Due to the strong electron withdrawing effect of the carbonyl grp and resonance stabilisation of the conjugate base
Aldol condensation
Must have Alpha H
Remove H2O for product
Reagent-Dil NaOH
Canizzaro rexn
No alpha H
2 molecules of aldehyde
One is reduced to alcohol while other is oxidized to carboxylic acid salt
Reagent-conc. KOH
ESR of aldehyde and ketone
Meta directing
For nitration-HNO3/H2SO4 at 273-283K
