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Questions of the Day:

Explore non-reactive scenarios, GC mechanisms, equations, NBS bromination, radical concepts, solvent properties, and more in this interactive learning session.

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Questions of the Day:

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  1. Questions of the Day: • The following Friedel-Crafts reactions do not work, i.e. no reaction. Why? (Think of mechanism…) • a) Toluene reacting with chlorobenzene in the presence of aluminum chloride catalyst • b) Benzaldehyde reacting with chloromethane in the presence of aluminum chloride catalyst

  2. Today: Conclusion of Friedel-Crafts/GC Introduction to NBS-Bromination (Exp. 3) MiniQuiz

  3. Friedel-Crafts Alkylations (Exp.II) Reaction equation for the reaction of p-xylene with 1-bromopropane in the presence of aluminum trichloride (our lab experiment): Mechanism… : Which carbocation intermediates are formed?

  4. Gas Chromatography • Which is the moving phase, which is the stationary phase in our GC? • What peaks do you expect to get in your GC of Exp.II? What determines their approximate sequence?

  5. II.Weight of product mixture What is in product mixture? Percent by weight of mono n-propyl product in product mixtureWeight fraction… Remember: Different molecular weights… Theoretical yield in grams of mono n-propyl product Balanced equation (assuming that only mono n-propyl product is formed), mols, mol ratios … Percent yield mono n-propyl product* [Actual yield / theor. yield] x % Ratio of n-propyl to isopropyl product* GC!Area ratio =mol ratio Calculations for Friedel-Crafts Experiment 3. 1. 4. 2.

  6. Synthesis of Bromoethylbenzene; H-NMR (Manual Exp.III) What is the structure of N-Bromosuccinimide (NBS)? What type of a reaction is this? • What is a “radical” in chemistry? • What is the geometry of a carbon radical? • What reaction conditions generally tend to lead to radical intermediates? • What are the major steps found in every radicalreaction?

  7. Synthesis of Bromoethylbenzene; H-NMR (Manual Exp.III) • Why does bromination in our reaction occur at the α-position only? • What is the function of NBS? • What is the function of dibenzoyl peroxide?

  8. Propagation How can you explain that the reaction mixture goes through a series of color changes?

  9. Synthesis of Bromoethylbenzene (Manual Exp.III) • Properties of CCl4? • Why is CCl4 a good solvent for our reaction mixture? • What are criteria for a "good solvent" in general? • What is the purpose of addingcyclododecane?

  10. Next time: • NMR (Concl. of Exp.3) • Introduction to Diels-Alder (Exp.4) • MiniQuiz on this lecture

  11. MiniQuiz 2 Question: Write the structures of two(2) carbocation intermediates that are formed during our Friedel-Crafts reaction (Exp.2)

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