Final answer:
Both PCC in dichloromethane and sodium dichromate in sulfuric acid with water can be used for the oxidation of a primary alcohol to an aldehyde, but PCC is preferred for controlled oxidation without overoxidation to a carboxylic acid.
Step-by-step explanation:
The conversion mentioned in the question suggests the transformation of a primary alcohol to an aldehyde. Oxidizing agents that can perform this reaction include A) PCC (Pyridinium chlorochromate) in CH₂Cl₂ (dichloromethane), which is a mild oxidant that stops at the aldehyde stage, and D) Na₂Cr₂O₇ (Sodium dichromate) in H₂SO₄ (sulfuric acid) with H₂O (water), which is a stronger oxidant and can further oxidize the aldehyde to a carboxylic acid under certain conditions. In this case, for a controlled oxidation to the aldehyde without further oxidation to the carboxylic acid, both reagents A (PCC/CH₂Cl₂) and D (Na₂Cr₂O₇/H₂SO₄/H₂O) can be used, but PCC/CH₂Cl₂ is more commonly preferred due to its milder nature.