The preparation of “azo” dyes often does not work well in the laboratory. Although the correct colour is usually apparent, very little product is obtained. Seeing this, a student decides to modify the experimental procedure and obtains a record quantity of product. Being very competitive, he does not want to let you in on his trick. However, you noticed that he added a liquid, and that he was monitoring the addition with pH paper. Knowing this, can you explain his high yield?

Just look at the lab manual at the formation of the NO+ ion... adding HCl pushes the equilibrium to the right according to LeChatelier's principle, increasing the amount of diazonium salt and in turn of dye. But the student still checks with litmus so that it does not become too acidic (that's bad!).

Think a little bit before just posting the question and waiting for the answer... Otherwise you will do really bad on the final!

how do you synthesize 1-propanol from the starting material butyraldehyde?

To synthesize 1-propanol from butyraldehyde, you can use a process called reduction. The most commonly used and efficient method for this conversion is using a reducing agent known as sodium borohydride (NaBH4). Here's a step-by-step procedure:

1. Set up a reaction flask with a reflux condenser and add butyraldehyde.
2. Dissolve sodium borohydride in a suitable solvent such as ethanol or water.
3. Carefully add the sodium borohydride solution dropwise to the butyraldehyde while stirring vigorously. The reaction mixture may become slightly exothermic, so be cautious and control the addition rate.
4. Continue stirring the reaction mixture for a period of time, usually a few hours, at a suitable temperature (room temperature or slightly elevated). This allows for complete reduction of butyraldehyde to 1-propanol.
5. After the required reaction time, quench the reaction by carefully adding water or dilute acid to destroy any excess sodium borohydride.
6. Extract the desired product, 1-propanol, from the reaction mixture using an organic solvent such as diethyl ether or dichloromethane.
7. Dry the organic solvent layer over a drying agent like anhydrous sodium sulfate or magnesium sulfate to remove any remaining water.
8. Finally, distill the dry solvent to obtain pure 1-propanol, which has a boiling point of around 97 degrees Celsius.

It's important to note that safety precautions should always be followed when working with chemicals and conducting experiments in a laboratory. Using appropriate protective equipment, such as goggles and gloves, and working in a well-ventilated area is highly recommended.