Concept explainers
a)
Interpretation:Solution recrystallization should be defined.
Concept introduction: Sublimation, extraction and chromatography are methods that are used for purification of organic compounds. But recrystallization involves isolation of compounds with extremely high purity. Recrystallization is one of techniques that are employed to purify organic compounds.
a)
Explanation of Solution
Solution recrystallization or simply recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
b)
Interpretation:Temperature coefficient of solvent should be defined.
Concept introduction:Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
b)
Explanation of Solution
Recrystallization solvent should be chosen in such way that compound is insoluble at low temperatures but becomes soluble at high temperatures. This variance in solubility of compound is governed by temperature coefficient of solvent.
c)
Interpretation:Relationship between dielectric constant and polarity of solvent should be defined.
Concept introduction:Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
c)
Explanation of Solution
Most commonly used solvents for recrystallization varies widely in terms of their polarities. These polarities are measured by respective dielectric constants. Solvents with dielectric constants from 2 to 3 are nonpolar while those with values of dielectric constants more than 10 are polar. Solvents with dielectric constant in range of 3 to 10 are considered as intermediate polar. Polar compounds are usually soluble in polar solvents and vice-versa. So polarity of solvent is directly related to dielectric constant.
d)
Interpretation:Petroleum ether should be defined.
Concept introduction: Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
d)
Explanation of Solution
Petroleum ether is generally used as solvent in recrystallization process. It is flammable and highly volatile in nature. It is also known as benzene. Chemical structure for petroleum ether does not contain ether functional group but consists of aliphatic hydrocarbons and has chemical formula of
e)
Interpretation:Mixed solvents should be defined.
Concept introduction:Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
e)
Explanation of Solution
If more than one solvent exists in mixture, it is termed as mixed solvent. So mixed solvents are usually made up of two or more types of single solvents. For example, isoamyl or banana oil is mixed solvent.
f)
Interpretation:Solvent selection should be defined.
Concept introduction: Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
f)
Explanation of Solution
Criteria mentioned below should be used to select solvent for recrystallization.
1. Solvent should be able to dissolve desired compound in itself at high temperatures but insoluble at low temperatures. In short, solvent with favorable temperature coefficient should be used for particular solute.
2. Solvent should be chosen in such way that impurities are either insoluble in it or remain moderately soluble in it at low temperatures.
3. Boiling point of desired solvent should be low so that it gets separated from crystals easily.
4. Boiling point of solvent should be less than melting point of solid under consideration.
5. There should be no reaction between solvent and substance that needs to be purified.
g)
Interpretation:Filter-aid should be defined.
Concept introduction:Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
g)
Explanation of Solution
Filter aid is substance or agent that is composed of solid particles and is used to improve efficiency of filtration. Its use also controls flow of liquids and removal of solid particles.
h)
Interpretation:Hot filtration should be defined.
Concept introduction: Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
h)
Explanation of Solution
Hot filtration is technique that is used in recrystallization process when insoluble solid impurities are present in solvent. This process is essential to follow when activated charcoal is used to remove colored impurities in recrystallization process.
i)
Interpretation:Seeding should be defined.
Concept introduction:Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
i)
Explanation of Solution
Seeding is method that is used to control supersaturation. Supersaturated solutions are allowed to form crystals by process of seeding. Any of crystals formed are added to solution to induce crystallization that occurs on rapid pace.
j)
Interpretation:Vacuum filtration should be defined.
Concept introduction: Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
j)
Explanation of Solution
Vacuum filtration is technique that is applied to separate solid products from liquids. It is performed with help of Buchner funnel that is attached to vacuum filter flask with aid of rubber stopper or neoprene adapter. Side arm of filter flask is attached to house vacuum line through trap called filter trap. This trap is used for collection of overflowed filtrate from filter flask.
k)
Interpretation:Mother liquor should be defined.
Concept introduction:Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
k)
Explanation of Solution
Mother liquor is nothing but part of solution that remains after crystallization of pure compound. This liquid is generally obtained in filtration process.
l)
Interpretation:Filtrate should be defined.
Concept introduction: Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
l)
Explanation of Solution
Filtration is procedure that is used to remove insoluble impurities, decolorized activated carbon from solution and also for purification of compound. Liquid that has been passed through filter apparatus is called filtrate while solid that cannot pass through filter is known as residue.
m)
Interpretation: Solute should be defined.
Concept introduction: Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
m)
Explanation of Solution
Solution always has two components, one is solute and another is solvent. Solute is that part of solution that is present in small quantity and that dissolves itself into another component called solvent. So solvent is present in larger amount in solution and it dissolves solute in itself.
n)
Interpretation: Solvent should be defined.
Concept introduction: Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
n)
Explanation of Solution
Solution always has two components, one is solute and another is solvent. Solute is that part of solution that is present in small quantity and that dissolves itself into another component called solvent. So solvent is present in larger amount in solution and it dissolves solute in itself.
o)
Interpretation:Occlusion should be defined.
Concept introduction: Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
o)
Explanation of Solution
Occlusion occurs when one substance is included into another one. This process usually occurs if crystallization or precipitation occurs at high speeds.
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Chapter 3 Solutions
EBK EXPERIMENTAL ORGANIC CHEMISTRY: A M
- How was the precipitate obtained after filtration? a. By drying the precipitate on the filter paper using a desiccator. b. By charring the filter paper and igniting the product in a crucible. c. By redissolving in hydrochloric acidarrow_forwardAcetone and isopropyl alcohol are generally not suitable for use in extraction, but are frequently used as recrystallization solvents. Explainarrow_forwardWhich statement about liquid-liquid extraction is not correct? * A- A solvent must be available that is miscible with the solution containing the substance to be extracted. B- The solvent used for extraction must have a good ability to dissolve the desired substance. C- The denser solution forms the bottom layer in the extraction funnel. D- The extraction funnel must be vented during the extraction procedure to prevent excessive build-up of pressure inside the extraction funnel. E- All these statements are correct.arrow_forward
- An overachieving student determines that their neutral liquid unknown contains impurities. Suggest at least one method that could be used to further purify the liquid compound.arrow_forwardBriefly describe on how peptization may occur during washing process of pure compoundarrow_forwardLet's assume that 5.6 g of crude product was isolated, and 4.19 g of pure product was collected after recrystilization 8. Let's assume that the melting point of the recrystallized product was 104-108°C. What conclusions can you draw? Provide a brief discussion of these results.arrow_forward
- Is recrystallization a good method for purifying any product?arrow_forwardWhich of the following should be done if there is no recrystallization due to the unsaturation of the solution? (mixed solvent recrystallization) a. Crystal seeding b. Scratching the inner walls or bottom of container c. Further boiling of solvent d. Adding small amount of samplearrow_forwardOccasionally you will have solid impurities “trash” in your heated recrystallization solvent. How do you remove these impurities?arrow_forward
- Why would a solvent with a very high boiling point be inappropriate for a recrystallization? Too much solvent would be lost to evaporation during the heating phase of the recrystallization Impurities and the compound to be recrystallized would dissolve equally well in this solvent A high boiling solvent would not dissolve the compound to be recrystallized It would be difficult to remove residual solvent from the purified crystalsarrow_forwardWhat is the effect of weighing a recrystallized organic solid which is not completely dried to the percentage yield? Elaborate.arrow_forwardneed this answer in detail. don't copy elsewhere I will downvote . A separation of the mixture of substances X and Y is carried out by extraction of Craig using an organic solvent of the same volume. What is the dissolved Y fraction in the 18th tube after 24 times of removal if Dy = 5 is knownarrow_forward
- EBK A SMALL SCALE APPROACH TO ORGANIC LChemistryISBN:9781305446021Author:LampmanPublisher:CENGAGE LEARNING - CONSIGNMENT