Background: Given an unknown mixture which contains either two or three of the following liquids: tetrahydrofuran (THF), cyclohexane, toluene, and o-xylene. While the order that the compounds leave the column is not always obvious, the column we are using is a polar environment and therefore we would expect less polar (lower boiling) compounds to spend the least time in the column.
Electronic Effects
The effect of electrons that are located in the chemical bonds within the atoms of the molecule is termed an electronic effect. The electronic effect is also explained as the effect through which the reactivity of the compound in one portion is controlled by the electron repulsion or attraction producing in another portion of the molecule.
Drawing Resonance Forms
In organic chemistry, resonance may be a mental exercise that illustrates the delocalization of electrons inside molecules within the valence bond theory of octet bonding. It entails creating several Lewis structures that, when combined, reflect the molecule's entire electronic structure. One Lewis diagram cannot explain the bonding (lone pair, double bond, octet) elaborately. A hybrid describes a combination of possible resonance structures that represents the entire delocalization of electrons within the molecule.
Using Molecular Structure To Predict Equilibrium
Equilibrium does not always imply an equal presence of reactants and products. This signifies that the reaction reaches a point when reactant and product quantities remain constant as the rate of forward and backward reaction is the same. Molecular structures of various compounds can help in predicting equilibrium.
Background: Given an unknown mixture which contains either two or three of the following liquids: tetrahydrofuran (THF), cyclohexane, toluene, and o-xylene. While the order that the compounds leave the column is not always obvious, the column we are using is a polar environment and therefore we would expect less polar (lower boiling) compounds to spend the least time in the column. In order to qualitatively confirm the identity of the peaks, you will make five different samples to analyze on the gas chromatograph: (a) your unknown, (b) unknown + THF, (c) unknown + cyclohexane, (d) unknown + toluene, and (e) unknown + o-xylene. Any new peak that appearsin relation to your unknown sample indicates that compound is not present in your unknown; furthermore, an increase in the size of a peak present in your unknown identifies that compound as a component of the mixture. Although not completely accurate, the areas of the peaks in your unknown will allow you to find the approximate percentage of each compound in the mixture.
Questions:
1. How would the resolution (separation into discrete peaks) be affected if you used a column ½ the length of the one you used today?
2. According to the label, the commercial glass cleaner Windex contains 8 ingredients: water, 2- hexoxyethanol, isopropanolamine, sodium dodecylbenzene sulfonate, lauramine oxide, ammonium hydroxide, a fragrance molecule, and blue dye. A sample of windex is analyzed by GC and only 7 compounds could be identified: sodium dodecylbenzene sulfonate could not be located in the chromatogram. Please offer an explanation that accounts for why this ingredient in Windex is not observed by GC?
3. What would happen to the retention time of a given compound if the carrier gas flow rate of the gas chromatograph is increased?
4. We are looking at reaction A→B via periodic GC analysis. Initially, we only see one peak in our chromatogram; however, over time we find that a new peak is growing while the original peak is shrinking. What is happening?
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