Hi, need to submit a 500 words paper on the topic Pyrolysis of Aryl Sulfonate Esters in the Absence of Solvent: E1 or E2. Week questions Schematic diagram 2. Two substances used as mobile phases in gas chromatography are Nitrogen and Helium.
3. There should be no liquid sample in the GC syringe needle when the sample is being ejected because the sample liquid will make the gas chromatography ineffective. The gas chromatography will be affected by development of thermoplastic septum after several injections. It causes fatigue in the plastic septum that limits the number of injections. The gas is needed pure and so, the liquid sample acts as impurities commonly referred to as ghost peaks.
4. If the column is heated above its limit temperature, the flow rate decreases because of the increased viscosity of the gas mobile phase.
5. Thermal conductivity detectors work by sensing the changes in thermal conductivity of the column effluent. It then compares it to the reference flow of the carrier gas. It happens because most compounds have their thermal conductivity less than the thermal conductivity of common carrier gasses. Therefore, the effluent thermal conductivity when an analyte elutes from the column is reduced. A detectable signal will be produced.
6. The column oven should have temperature above the dew point of the least volatile component in the sample because low temperatures produces the greatest level of separation. The temperature should be above the dew point of the least volatile component in order to avoid condensation from occurring in the column.
7. A gas chromatogram shows a ‘peak’ whose area is proportional to the number of molecules generating the signal.
8. a. When carrier gas flow rate is too high, the separation will become poor because reduction in the retention times. This is because the components have very little time to interact with the stationary phase. Too slow flow rate of the carrier gas reduces the analysis, but there is a better separation.
b. Too high temperature results in poor separation. Reason is that the retention time is short and the components stay in the gas phase. Too low temperature lower temperature results in better resolution. Because of the longer retention time.
9. The retention time of the components in a sample mixture is determined by air peak for TCD measurement done using packed column.
10. Molecular properties that separation of substances using GC is based on are polarity, boiling point and solubility.
Week 2 questions
1. a) boiling point of water at 25 torr = 95⁰
b) The water does not boil at 25⁰ and 25 torr. It is because temperature and pressure are no sufficient.
c) Assumptions made in Claussius-Clapeyron equation are. liquid’s molar volume is smaller than vapor, the vapor is an ideal gas and that the heat of vaporization is independent of temperature.
e) Vacuum distillation is necessary. It is the only method that can be used to distill
2. Device used to measure pressure inside a vacuum distillation apparatus is called a spinning rotor gauge.
3. The superscript value refers to temperature.
4. Boiling point range in a vacuum distillation is bigger than in simple distillation because of the lower external pressure.
5. A single solvent is used in the experiment for recrystallization of the reaction product
6. The E1 reaction does not involve the base and thus, the rate of reaction does not depend on the concentration of the base but on the concentration of the substrate. The reaction is in the rate-limiting step where there is formation carbonation.
7. The rate of E2 reaction depends on both concentration of base and substrate because the reaction is the rate-determining step. A strong base allows for the displacement of the polar leaving group.
8. Factors affecting rate of E1 reaction are leaving group, identity of R group, Type of solvent and heat.