Q25E - Organic Chemistry (Mcmurry)

Question

Assume that you are in a laboratory carrying out the catalytic hydrogenation of cyclohexene to cyclohexane. How could you use a mass

spectrometer to determine when the reaction is finished?

Step-by-Step Solution

Answer

When the reaction is finished, the mass spectrum of the reaction mixture should be superimposable with the mass spectrum of cyclohexane

Step 1: Catalytic Hydrogenation

Catalytic hydrogenation is treatment with hydrogen in presence of catalyst such as nickel, palladium or platinum. It is used to convert alkenes and aromatics into saturated alkanes and cycloalkanes which are less toxic and less reactive as wellas less corrosive.

Step 2: Mass Spectrometer

The mass spectrometer is an instrument which generate a beam of positively charged ion from the sample under investigation.

It separates these positively charged ions according to their mass to charge ratio.

Mass spectrometer record the relative abundance of separated each ions and result displayed on chart as Mass spectrum.

Step 3: Determine when the reaction is finished using Mass spectrometer

As, is different for each compound. After the reaction is underway, inject a sample from the reaction mixture in to the mass spectrometer. If the reaction is finished, the mass spectrum of the reaction mixture should be superimposable with the mass spectrum of cyclohexane.