Why can't anhydrous calcium chloride be used to dry ethanol, aldehydes, or ketones?

Why can't anhydrous calcium chloride be used to dry ethanol, aldehydes, or ketones?
Anhydrous calcium chloride is a widely used neutral desiccant in labs and industry, but its application has clear chemical limits. It forms stable complexes with oxygen-containing organics: ethanol yields CaCl2·4C2H5OH, which does not decompose on heating, making CaCl2 unsuitable for drying alcohols. Ketones like acetone also coordinate strongly via carbonyl oxygen and should be avoided. Ethers can be dried with CaCl2 only if peroxides are first removed and the complex decomposes on distillation. In practice, this means buyers must match desiccant grade to the target stream. For gas drying, CaCl2 works well for most neutral and acidic gases but fails with ammonia, forming CaCl2·8NH3. Understanding these reactivity boundaries is essential for process design and for avoiding contamination that leads to off-spec products or equipment fouling.