Aldehydes Ketones and Carboxylic acids 2

Question 1

Directly RMgX is not added to RCOCl, it is converted to R2Cd.

Answer 1

Since Grignard Reagent is very reactive it will react with ketone, so formed as the pdt and form 3o alc to prevent this, it is converted to R2Cd.
- The yield of ketones is very high in this ketone.

Question 1

How is the C=O, pi bond different from the C=O.
why carb acids do not give nu- addn?

Answer 1

In C=O the pi electrons is the alkene do not have any direction.
Therefore the nu- addn is not taking place they will have only X2, H2SO4, HX, whereas the pi e-s of C=O are always directed towards the oxygen which makes the nu- addn easier.
therefore carb acids do not give nu- addn

Question 2

aliphatic aldehydes is more prone to nu- addn than aromatic aldehydes

Answer 2

• (-R) effect of aldehydic grp which decreases the electrophilicity of the carbonyl carbon.
• Aromatic aldehydes are greater than aromatic ketones due to greater steric hindrance.

Question 3

____ is teh ketone that is least reactive

Answer 3

acetophenone

Question 4

aldehydes are more easily oxidized thana ketone. give reason.

Answer 4

Due to teh presence of H atom in the carbonyl C which can be easily converted to -OH gp without involving cleavage of bond.
in ketones cleavage of C-C bond is difficult.
aldehydes are good reducing agents due to teh presence of the C=O therefore aldehydes can wasily be oxidized by weak OR like Cu2+, Ag+, Br2-, etc…
ketones req strong OR like conc HNO3, K2Cr2O7/H2SO4,etc…

Question 5

Why benzaldehyde (aromatic aldehydes) do not give fehlings rgnt?

Answer 5

DU eto the -R effect of teh aldehyde gp, the e- density on the C of the carbonyl gp increases which makes CH bond strong, Only strong OA can oxidize.
They answer only tollens not fehlings.

Question 6

The weak nu-, alc, ammonia can attack the C=O in the presence of the acid, dry HCl.

Answer 6

dry HCl, protonates the Oxygen of the C=O.
it increases teh electrophilicity of the carbonyl C for the oxidation.

Question 7

benzaldehyde to cinamaldehyde

Answer 7

cross aldol condensaidtion btwn, Benzaldehyde and acetaldehyde.

Question 8

benedict soln

Answer 8

alk. CuSo4 - blue color
when added to aliphatic ald changes to red colour
used in clinical laboratory to test for blood glucose.

Question 9

benzoic acid is a stronger acid than CH3COOH

Answer 9

• The ring has a strong -T effect which decreases the e-density that increases teh acideic strength also benzoate ion is more resonanve stabilized.
• in the benzoate anion the benzoic acid, the CH3 is attatched to the sp2 hybridized C atom.
  in CH3COO- anion the CH3 is attatched to teh sp3 hybridized C atom.

the acidic strength depeds on the hybridization of C atom to which teh COOH is attatched.

Question 10

benzoic is a stronger acid than acrolein.

Answer 10

though both having teh same sp2 hybridized C atom. benzoic acid is stronger due to the delocalization which destroys the aromatic character of the benzene ring.