There are many reagents that have been developed to oxidize alcohols to ketones or aldehydes. The chromium reagents work very well, but other procedures are preferred. Why do you suppose that other reagents are favored? What are the hazards of using \(\mathrm{Cr}(\mathrm{VI})\) ?

Oxidation of alcohols is a fundamental chemical process. It involves the conversion of alcohols into aldehydes, ketones, or carboxylic acids. To achieve this, we use substances called oxidizing reagents.
These reagents either add oxygen to, or remove hydrogen from, the alcohol molecule. For instance, a primary alcohol can be oxidized to an aldehyde and further to a carboxylic acid, while a secondary alcohol typically oxidizes to a ketone.
Commonly used reagents for this process include strong oxidizers like potassium permanganate and milder ones like pyridinium chlorochromate (PCC). Understanding how each reagent works is key to successfully performing these transformations.

Chromium reagents, such as chromium trioxide \(\text{CrO}_3\) and chromic acid, play a key role in the oxidation of alcohols. They are highly effective in converting alcohols to corresponding aldehydes and ketones.
These reagents contain Cr(VI), which is in the +6 oxidation state and highly reactive. Cr(VI) compounds like Jones reagent (chromic acid in acetone) and PCC (pyridinium chlorochromate) are popular choices.
Interestingly, PCC is preferred for its selectivity; it can oxidize primary alcohols to aldehydes without further oxidation to carboxylic acids. Despite their effectiveness, the use of chromium reagents comes with serious drawbacks.

Using \(\text{Cr(VI)}\) compounds poses severe safety hazards due to their toxic and carcinogenic nature. Exposure to these chemicals can lead to serious health risks, including skin irritation and lung cancer.
Consequently, strict safety protocols are essential when handling these compounds. This involves wearing protective equipment like gloves and goggles, and ensuring proper ventilation.
Environmental concerns also play a factor. Cr(VI) is not only harmful to humans but is also a significant environmental pollutant. Disposal of these chemicals must adhere to rigorous guidelines to prevent contamination.
Due to these risks, many chemists prefer alternative, greener oxidizing agents like TEMPO or Dess-Martin periodinane, which offer safer handling and lower environmental impact.