Unit 11:Ketones and aldehydes
Typical bond angles between the carbonyl group and its substituents show minor deviations
from the trigonal planar angles of 120 degrees, with a slightly higher bond angle between the
O=C-R bond than the R-C-R bond on the carbonyl carbon (with R being any substituent).
86.3 Preparing Aldehydes and Ketones
86.3.1 Preparing Aldehydes
Partial oxidation of primary alcohols to aldehydes
This reaction uses pyridinium chlorochromate (PCC) in the absence of water (if water is
present the alcohol will be oxidized further to a carboxylic acid).
Figure 180
From fatty acids
(HCOO)2Ca + HEAT ----> HCHO + CaCO3 (CH3COO)2Ca + HEAT ----> acetone +
CaCO3 (CH3COO)2Ca + (HCOO)2Ca ---->ethanaldehyde
Stephen reduction
RCN + SnCl2+ HCL ----> RCH=NH 2 +Cl−----> on hydrolysis gives RCHO
Here sulfur is used as a poisoner so that aldehyde formed doesn’t get oxidised to the car-
boxylic acid. See the Wikipedia article^1 for more detail. mechanism b to do wikipedia kis
naam ka hai ye
Rosenmund reaction
RCOCl + Pd + BaSO4 + S ---->RCHO for solvent xylene is used
1 https://en.wikipedia.org/wiki/Stephen%20aldehyde%20synthesis