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Questions and Answers
What is placed in a 2-l round-bottomed flask?
What is placed in a 2-l round-bottomed flask?
- 390 g of aniline hydrochloride and 190 g of urea
- 250 g of pinacol hydrate and 750 g of 6 N sulfuric acid (correct)
- 750 g of pinacol hydrate
- 750 g of 6 N sulfuric acid and 250 g of urea
How many moles of pinacol hydrate is used in the process?
How many moles of pinacol hydrate is used in the process?
- 5.42 moles
- 2.42 moles
- 4.42 moles (correct)
- 3.2 moles
What is the boiling point range of the pinacolone?
What is the boiling point range of the pinacolone?
- 120–125°C
- 110–115°C
- 103–107°C (correct)
- 95–100°C
What is added to the water after the first distillation?
What is added to the water after the first distillation?
What is the yield of pinacolone from one run of the process?
What is the yield of pinacolone from one run of the process?
What is the purpose of redistillation of the pinacolone?
What is the purpose of redistillation of the pinacolone?
What is the ratio of aniline hydrochloride to urea in the solution?
What is the ratio of aniline hydrochloride to urea in the solution?
How is the carbanilide washed?
How is the carbanilide washed?
What is the type of bond cleavage where the shared pair of electrons remains with one of the fragments?
What is the type of bond cleavage where the shared pair of electrons remains with one of the fragments?
What is the term for the energy required to cleave a chemical bond?
What is the term for the energy required to cleave a chemical bond?
What is the term for the species that donate a proton?
What is the term for the species that donate a proton?
What type of bond cleavage produces electrically neutral fragments called free radicals?
What type of bond cleavage produces electrically neutral fragments called free radicals?
What is the term for the process where the bond breaks in such a way that the shared pair of electrons is divided equally between the products?
What is the term for the process where the bond breaks in such a way that the shared pair of electrons is divided equally between the products?
What is the term for the species that accept a proton?
What is the term for the species that accept a proton?
What type of bond cleavage requires the bond to be polarized, leading to the separation of oppositely charged ions?
What type of bond cleavage requires the bond to be polarized, leading to the separation of oppositely charged ions?
What is the example of a molecule that undergoes hemolytic cleavage?
What is the example of a molecule that undergoes hemolytic cleavage?
What is the temperature range of the ligroin used in the purification process?
What is the temperature range of the ligroin used in the purification process?
What is the melting point of the purified benzopinacol?
What is the melting point of the purified benzopinacol?
What is the percentage yield of benzipinacol in the first reduction?
What is the percentage yield of benzipinacol in the first reduction?
What is the name of the reaction that involves the coupling of 2 aryl halides in the presence of sodium metal in dry ethereal solution?
What is the name of the reaction that involves the coupling of 2 aryl halides in the presence of sodium metal in dry ethereal solution?
What is the role of acid in the pinacol-pnacolone rearrangement?
What is the role of acid in the pinacol-pnacolone rearrangement?
What is the result of the removal of a water molecule in the first step of the pinacol-pnacolone rearrangement mechanism?
What is the result of the removal of a water molecule in the first step of the pinacol-pnacolone rearrangement mechanism?
What is the product of the pinacol-pnacolone rearrangement?
What is the product of the pinacol-pnacolone rearrangement?
How many portions of benzophenone can be reduced using this procedure?
How many portions of benzophenone can be reduced using this procedure?
What is the difference between basicity and nucleophilicity?
What is the difference between basicity and nucleophilicity?
What is the trend in nucleophilicity as electron density increases?
What is the trend in nucleophilicity as electron density increases?
What is the role of solvent in nucleophilicity?
What is the role of solvent in nucleophilicity?
What is the relationship between the conjugate base and nucleophilicity?
What is the relationship between the conjugate base and nucleophilicity?
What is the PKa of hydroxide ion?
What is the PKa of hydroxide ion?
What is the difference between hydroxide ion and cyanide ion?
What is the difference between hydroxide ion and cyanide ion?
What is the effect of steric hindrance on nucleophilicity?
What is the effect of steric hindrance on nucleophilicity?
What are the four key factors that contribute to nucleophilicity?
What are the four key factors that contribute to nucleophilicity?
What is the optimal temperature range for the reaction mixture to prevent spontaneous decomposition of the diazonium salt?
What is the optimal temperature range for the reaction mixture to prevent spontaneous decomposition of the diazonium salt?
What is the purpose of adding 10 drops of concentrated HCl to the aniline solution?
What is the purpose of adding 10 drops of concentrated HCl to the aniline solution?
What is the role of 2-naphthol in the azo coupling reaction?
What is the role of 2-naphthol in the azo coupling reaction?
Why is it important to add the NaNO2 solution slowly to the aniline solution?
Why is it important to add the NaNO2 solution slowly to the aniline solution?
What is the purpose of stirring the mixture in the ice-water bath for 3-5 minutes?
What is the purpose of stirring the mixture in the ice-water bath for 3-5 minutes?
What is the purpose of vacuum filtering the precipitates?
What is the purpose of vacuum filtering the precipitates?
What is the role of β-naphthol in the synthesis of Sudan I?
What is the role of β-naphthol in the synthesis of Sudan I?
Why is it necessary to chill the NaNO2 solution in the ice-water bath?
Why is it necessary to chill the NaNO2 solution in the ice-water bath?
Study Notes
Bond Cleavage
- Hemolytic cleavage (homolysis): a cleavage of a covalent bond in which the two electrons are divided equally between the products, resulting in electrically neutral fragments called free radicals.
- Example: Br-Br → 2Br·
- Heterolytic cleavage (heterolysis): a cleavage of a covalent bond in which the shared pair of electrons remains with one of the fragments, resulting in ions.
- Example: R-CH2-X → R-CH2+ + X-
Bond Dissociation Energy
- The amount of energy required to cleave a chemical bond.
Acid-Base Reactions
- Bronsted-Lowry definition of acids and bases:
- Acids: species that donate a proton (H+)
- Bases: species that accept a proton
- Example: HO- + H2O → H2O + HO-
Nucleophilicity
- Factors that make a good nucleophile:
- Charge: a nucleophile is more effective when it is electron-rich
- Electronegativity: a nucleophile is more effective when it has a high electronegativity
- Solvent: the solvent can affect the nucleophilicity of a species
- Steric hindrance: the size and shape of the nucleophile can affect its ability to attack
- Basicity is a subset of nucleophilicity: a nucleophile can donate a lone pair of electrons to a hydrogen atom (basicity) or to any other atom (nucleophilicity)
Pinacol Rearrangement
- A method for converting a 1,2-diol to a carbonyl compound
- Mechanism:
- Protonation of the hydroxide ion
- Formation of a carbocation
- Rearrangement to form a new bond
- Removal of a hydrogen ion to form the product
- Procedure:
- Mix pinacol hydrate with sulfuric acid
- Distill the mixture until the upper layer of distillate ceases to increase in volume
- Repeat the process several times to obtain the desired product
Synthesis of Sudan I
- A two-step synthesis:
- Activation of 2-naphthol under alkaline conditions to form 2-naphtholate
- Azo coupling with the diazonium salt to form the Sudan I dye
- Procedure:
- Mix aniline with water and HCl
- Chill the mixture in an ice-water bath
- Add NaNO2 solution to the aniline mixture
- Stir the mixture and transfer it to a beaker containing β-naphthol
- Stir the mixture in the ice-water bath for 3-5 minutes
- Vacuum filter the precipitates and wash with cold water
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Description
Learn about the two classifications of bond cleavage, Hemolytic cleavage, and its characteristics in a covalent bond. Understand the formation of free radicals and electronically symmetrical bond cleavage.
