Alkylation On Graphite: Introduction to Green Technologies

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Alkylation On Graphite: Introduction to Green Technologies

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1. Alkylation On Graphite: Introduction to Green Technologies

2. Friedel – Crafts Alkylation Synthesis of alkyl benzenes from alkyl halides and a Lewis acid, usually AlCl3.

3. Friedel – Crafts Alkylation Reactions of alkyl halide with Lewis acid produces a carbocation. The carbocation will act as an electrophile.

4. Friedel – Crafts Alkylation

5. Limitations of Friedel – Crafts Alkylation Only alkyl halides can be used (F, Cl, I, Br). Aryl halides and vinylic halides do not react (their carbocations are too hard to form).

6. Limitations of Friedel – Crafts Alkylation If you have electron withdrawing group, then there won’t be any alkylation.

7. Limitations of Friedel – Crafts Alkylation Multiple alkylations occur because first one activate the ring.

8. Limitations of Friedel – Crafts Alkylation

9. Today’s Task Alkylation of p – Xylene with 2 – bromobutane using graphite. Learn about Green Technologies. Characterization by 1H and COSY NMR.

10. Allotropes of Carbon Diamond is very strong due to tetrahedral arrangement.

11. Allotropes of Carbon Graphite is a soft material due to hexagonal arrangement.

12. Allotropes of Carbon Fullerene and Carbon Nanotubes have similar structure to Graphite.

13. Allotropes of Carbon Amorphous Carbon does not have any crystalline structure like Diamond or Graphite.

14. Why we choose Graphite??? It is Cheaper. Graphite acted as catalyst for: 1. Friedel – Crafts Benzoylation of Aromatic Compounds 2. Cleavage of Ethers by Acyl Halides. Graphite Doped Metal Halides acted as catalyst for electrophilic alkylation of aromatic compounds.

15. Procedure Take 100 mL RB flask and add: 1. 5 mL of p – Xylene. 2. 0.44 mL of 2 – bromobutane. 3. 0.5 gram of graphite. Set up a refluxion apparatus and do the refluxion for 1 ½ hour. Circulate Cold water during refluxion.

16. Procedure Cool the reaction mixture to room temperature. Filter the graphite using Frit funnel. Wash the Graphite with 15 mL of hexane. Dry the Graphite in the air for 10 more minutes and return to me.

17. Procedure Transfer the filtrate into a fresh and dry RB flask. Evaporate all the solvents using rotary evaporator. Once you removed all the solvents; weigh the product (it’s a liquid).

18. Procedure Do the evaporation one more time and weigh the product. If you get the consistent weight then you calculate the percent of yield. If you don’t get the consistent value, do the evaporation till you get consistent weight.

19. Chemical Reaction

20. Mechanism Partial Charge on alkyl halide may be produced by: 1. Metal Impurities in the Graphite 2. ? electrons in the Graphite Formation of the Transition State is still Enigmatic. Dr. Serada’s research group is trying to find the exact mechanism and they found reactivity of halide in the following order. Tertiary Halide > Secondary Halide. No Reaction occurred with Primary Halide

21. Green Chemistry By definition: Green Chemistry is the design, development, and implementation of chemical products and processes to reduce or eliminate the use and generation of substances hazardous to human health and the environment. Advantages: 1. Reduce Pollution 2. Low Cost 3. Simplicity in Process and Handling

22. Green Chemistry: Example

23. Green Chemistry Why Today’s reaction is Environmental Free??? 1. No need of using strong Lewis Acid catalysts. 2. Catalysts can be Reusable. 3. Produces Minimum Waste. 4. Simple Procedure. 5. Low cost. 6. No Toxic Reagents. 7. High Yield and less by – products.

24. Characterization 1H NMR and COSY Spectrum. COSY (CORRLATED SPECTROSCOPY) is 2D NMR. One dimensional NMR involves with only one Radio Frequency pulse. Where as 2D consists of a sequence of Radio Frequency (RF) pulses with delay period of time.

25. Characterization Involves a series of one dimensional (1D) experiments. 1. COSY use to have two 1D 1H NMR spectrum

26. Characterization Intensities of the peaks in the spectrum can be represented using 3D. 1. Contours 2. Different Color The diagonal peaks are intensities for particular signal.

27. Characterization Two kinds of peaks are in 2D NMR. 1. Diagonal Peak: The peaks on the diagonal called Diagonal Peaks. 2. Cross Peak: The peaks off the diagonal called Cross Peaks. The peaks on the diagonal when matched with cross-peaks are coupled each other (means those two protons are from adjacent carbon).

29. Characterization ID proton NMR can tell about: 1. Chemical Shift value 2. Number of Protons 3. Multiplicity You cannot easily differentiate between two singlet and a doublet using 1D 1H NMR. It is not very easy to interpret a complex 1D 1H NMR (NMR of Natural Products). But COSY helps very well to solve the above difficulties.

30. Characterization

31. Notes Work Four People together. Do not throw the used Graphite. Do not contaminate any chemicals.

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