CHE 327 Quiz 2: Organic Chemistry Experiments

Study Notes

The quiz is based on experiments related to the isomerization of dimethyl maleate, extraction of β-carotene, synthesis of a fragrant ester, and multistep synthesis of lidocaine.
The quiz includes spectroscopy (GC, IR, and NMR) and requires the use of a Scantron answer sheet.

Students need to bring their university ID, pencil, eraser, pen, and a calculator to the exam.
No borrowing of calculators or communication/collaboration with other students is allowed during the exam.

In column chromatography, the earliest fraction from the column can be determined by analyzing the developed TLC plate.
The earliest fraction is the one that travels the farthest on the TLC plate.

Chromatography is a technique used to separate mixtures based on differences in adsorption of analytes to an adsorbent.
It involves the separation of compounds or ions by distribution between a stationary phase and a moving phase.
The stationary phase can be a solid or liquid, while the mobile phase can be a liquid or gas.
Chromatography can be used to separate, purify, and determine the purity of compounds, as well as confirm their identity.

In TLC, the stationary phase is Silica (SiO4) immobilized on an aluminum back, although Alumina (Al2O3) and cellulose can also be used.
The mobile phase is a solvent that climbs up the TLC plate by capillary action, allowing analyte molecules to migrate up the plate.
The polarity of the solvent affects the migration of analytes, with increasing polarity causing all compounds to move faster.
Non-polar compounds move faster, while polar compounds move slower due to their interaction with silica.

Less polar molecules migrate faster on a polar stationary phase, while polar molecules move less due to their interaction with silica.
The polarity of the analyte affects its migration, with more polar analytes moving slower and less polar analytes moving faster.

Rf is the ratio of the distance traveled by the analyte to the distance traveled by the solvent.
It is a quantitative measure of the distance traveled by an analyte relative to the solvent in a TLC experiment.
Rf values can be used to identify compounds, with different compounds having unique Rf values.

TLC can be used to confirm the identity of a compound by comparing its Rf value to that of a known compound.
If two pure samples have different Rf values, they are likely to be different compounds.
If two pure samples have the same Rf values, they might be the same compound, but additional data is needed to confirm this.
TLC can also be used to determine the purity of a sample, with impure samples showing multiple spots on the TLC plate.

The isomerization reaction involves the conversion of one compound to another with the same molecular formula but a different structure.
The reaction can be monitored using TLC, with the appearance of new spots on the TLC plate indicating the formation of new compounds.

The lab procedure involves monitoring the progression of the isomerization reaction using TLC, with samples taken at regular intervals.
The reaction mixture is spotted on the TLC plate, and the resulting chromatogram is analyzed to determine the presence of different compounds.
The endpoint of the reaction is determined by observing the disappearance of the starting material and the formation of the product.

Bromine (Br2) is a highly toxic substance that can cause severe health problems if inhaled or ingested.
It is also a skin and eye irritant, and can cause environmental toxicity.
Safety precautions, including wearing rubber gloves, are necessary when handling bromine.
Other substances, such as methylene chloride and dimethyl maleate, also have potential health hazards and require proper handling and safety precautions.