Alcohol 3 :
Problem
Solution
When CrO3 suspended in
CH2Cl2 (in which it is virtually insoluble) is
treated with pyridine 3 (pyr.), a soluble bis-pyridine complex
is formed (Collins' reagent). The non-bonding electrons of pyridine
coordinate with the electron deficient chromium atom. There is no water present. Propionaldehyde 2 is
formed. Oxidation stops at the aldehyde. Oxidation to a carboxylic
acid does not occur in the absence of water. See Problem 2 in
Alcohols. But there is a
complication that may arise. Think about how an alcohol can react
like water, then click
here.