In another experiment, toluene is acetylated via Friedel Crafts reaction. The co

Question

In another experiment, toluene is acetylated via Friedel Crafts reaction. The collected product turned out to be a mixture of degree Oho, meta and pars isomers of the product expected. Using the gas chromatograph picture below, determine what percentage of the isomers is represented in each peak? Determine the retention times for each peak (isomer). If peak 13 is the pars isomer, how would you confirm this by running a pure sample of the pars isomer through the GC? What piece of data should be identical when running the mixture of isomers through the GC and running the Pure sample through the GC? Suggest a type of GC column (mobile phase and stationary phase combined), an inlet port temperature and column temperature at which to run the GC to separate the mixture of the three isomers. The three isomers all have normal boiling points in a range from 184-217 degree C.

Explanation / Answer

Gas chromatography produces/ distinguishes the different compounds in a mixture on the basis of their different retention times. When performed acylation to toluene, the mixture of -ortho, -para and -meta acetylated products are distinguished analytically through gas chromatography by their different retention times. Moreover, retention time is characterstic to every compound while it is in pure form or in mixture.

1. The peak areas represents percentage of isomers present in the mixture, as per the reaction properties (-ortho, -para directed reaction due to +I effect of CH3 group) the para isomer is major than the ortho and than to meta isomer.

Here, you are provided an analogous qualitative chromatogram. This GC-chromatogram is the plot of peak intensity versus retention time (X-axis). However, here it appears to be ortho, para and meta isomers from left to right.

2. On x-axis, it is plotted by taking retention times as the measurement. The perpenduclar line of each peak on x-axis represents its retention time. Retention times of the components in the mixture are in the order, ortho < para < meta.

3. Second/ middle peak (B) is for para isomer and tis retention time is same when we run the sample whether in pure or in mixture form. So you by retention time you can predict the isomer when pure form of compound is allowed to run.

4. Recommended stationary phases for these type of compounds: SPB-624, OVI-G43, VOCOL, SPB-20, Equity-1701, SPB- 35 SPB-50, SPB-225, PAG, Omegawax, SPB-1000, Nukol, SUPELCOWAX-10

Typical carrier gases used are helium, argon, hydrogen, nitrogen and air.

The temperature maintained in GC-chromatogram is such that at which the stationary phase can able to withstand. the temperature you can maitain about 280-360 oC.

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.