Interpretation:
The solvent that will be better to separate the mixture of compounds A and B should be determined.
Concept introduction:
Thin-layer chromatography is an analytical technique used to identify whether two compounds are identical or not and also to find the number of compounds in a mixture.
Metal, glass or plates made of plastics are utilized in TLCthatare coated bya thin layerof adsorbent and it acts as a stationary phase. The stationary phase usually used is polar silica gel. A mixture of solvents or single pure solvent is the mobile. It is also known as a developing agent. Mostly nonvolatile solid organic samples are analyzed by thin-layer chromatography.However, TLC cannot be used for volatile liquid compounds because it leads to loss of the sample by evaporation from the TLC plate.
In TLC analysis, mixture in a low quantity is taken for separation and dissolved in the suitable solvent and applied on the TLC plate. Then TLC plate is kept in the closed chamber immersed in mobile phase known as developing solvent. Through capillary action the solvent rises on the stationary phase. As the solvent rises on the plate, the sample is distributed between the mobile phase and the stationary phase on the basis of their retention values. The more the compound interacts with the stationary phase, the more slowly it moves on the TLC plate. When silica gel that is polar in nature behave as the stationary phase then mobile solvent rises with the nonpolar substances up on the plate most rapidly. In the chromatogram the polar substances rises up plate with lowest rate.
The ratio of distancescovered by the compound to thedistance covered by developing solvent or mobile front is known as retention factor
The
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Chapter 18 Solutions
Laboratory Techniques in Organic Chemistry
- Consider the following errors that could be made when running TLC. Indicate what should be done to correct the error.a. A two-component mixture containing 1-octene and 1,4-dimethylbenzene gave only one spot with an Rf value of 0.95. The solvent used was acetone.b. A two-component mixture containing a dicarboxylic acid and tricarboxylic acid gave only one spot with an Rf value of 0.05. The solvent used was hexane.c. When a TLC plate was developed, the solvent front ran off the top of the plate.arrow_forwardIf we were to use Toluene as a solvent in a TLC with benzophenone, diphenyl methanol, and biphenyl what would the the position of the TLC be? Use the structure of the compounds to explain why their elute up at different rates.arrow_forwardEvery spot on a student's TLC plate has an Rf value from 0.1 to 0.2. The student used a 10% ethyl acetate 920%0% pentane mixture as the eluting solvent. What composition might yield better Rf values for separating the compounds? 100% pentane 5% ethyl acetate and 95% pentane 20% ethyl acetate and 80% pentanearrow_forward
- When naphthalene, butyric acid, and phenyl acetate are separated using dichloromethane as the developing solvent on a silica gel TLC plate, which compound would have the highest Rf value? Which would have the lowest?arrow_forward1,8-Cineole is a predominant terpene found in cranberries. The concentration of 1,8-cineole in cranberries was determined using gas chromatography. A 5.00 g sample of freeze-dried cranberry powder was added to 10.0 mL water to form a cranberry extract. The extract was filtered. A 1.00 mL aliquot was added to a 25 ml volumetric along with a known amount of internal standard (d-14 cymene) and diluted to volume with water. Standards were spiked with a fixed amount of d-14 cymene as internal standard. The following data was obtained: 1,8-Cineole (ug/mL); 1,8-Cineole (peak area); d-14 cymene (peak area) 10.0; 1260; 1880 15.0; 1865; 1850 20.0; 2520; 1855 50.0; 6280; 1865 Sample; 1976; 1840 What is the concentration of 1,8-cineole in ug per gram of cranberry? O 398 ug/g O 159 ug/g O 674 ug/g O 796 ug/g O 15.9 ug/garrow_forwardA thin-layer chromatography (TLC) experiement was run using three compunds: benzophenone, benzhydrol, and biphenyl. The three solvents that were used with the three compounds were hexane, ethyl acetate, and dichloromethane. Which solvent would be the best for separating these compounds and why?arrow_forward
- A student has a green dye mixture on which she performs a TLC experiment with a silica gel plate and acetone as the solvent. She obtains a yellow spot with an Rf of 0.75 and a teal spot with an Rf of 0.45. Explain the significance of her data.arrow_forwardc. Often chemists are synthesizing a new molecule, we can only compare the reaction mixture to the starting material. According to the following TLC plate, is the reaction complete? Why or why not? A: Starting material B: Reaction mixture A Barrow_forwardIn what order would the following compounds be eluted on a silica gel TLC plate if they are spotted on the same plate and developed in a solvent mixture of 10:1 hexanes:ethyl acetate A. 1 has the highest Rf value, then 2 then 4 then 3 b. 4 has the highest Rf value, then 1 then 3 then 2 c. 3 has the highest Rf value, then 2 then 1 then 4 d. 2 has the highest Rf value, then 3 then 1 then 4arrow_forward
- You and another student were each given an unknown compound. Both samples contained colorless material. You each used the same brand of commercially prepared TLC plate and developed the plates using the same solvent. Each of you obtained a single spot of Rf = 0.75. Were the two samples necessarily the same substance? How could you prove unambiguously that they were ily identical using TLC?arrow_forwardWhy is distillation of cyclohexanol using acid catalyst phosphoric acid a better technique to purofy rather than extraction, recrystallization, chromatography, IR spectroscopy?arrow_forwardMatch column A with Column B. Given: Samples were spotted on the TLC plate and after performing the experiment, the following were obtained: Component A, Rf = 0.2 B, Rf = 0.5 C, Rf = 0.8 Which is the most polar? A. Component A v Which can dissolve in water? B. Component B Which has affinity to the stationary phase? c. Component C Which has affinity to mobile phase? Which is the least polar Which can dissolve in organic compounds? v Which component is slightly hydrophobic and hydrophilic? Activaarrow_forward
EBK A SMALL SCALE APPROACH TO ORGANIC LChemistryISBN:9781305446021Author:LampmanPublisher:CENGAGE LEARNING - CONSIGNMENT