Lecture 7

1. Lecture 7 Nitration and Iodination of aromatic compounds WWU -- Chemistry

2. Schedule • Brown labs with be doing nitration of methyl benzoate • Green lab will be doing iodonation of various activated aromatic compounds. Download experimental procedure from web. WWU -- Chemistry

3. Nitration of Methyl Benzoate Brown laboratories Experiment 40 WWU -- Chemistry

4. Reading Assignment • pp. 342 – 346 (Experiment 40) • 479-480 • Techniques 1, 2, 3, 10 • Technique 5, pp. 561-566; 569-574 • Technique 19, p. 746-753 • NOTE: We will use the “dry film” method, described on page 753 • Chapter 22 from the lecture textbook WWU -- Chemistry

5. Main Reaction This is an example of Electrophilic Aromatic Substitution (EAS). WWU -- Chemistry

6. Mechanism of Aromatic NitrationStep 1: Where does the electrophile come from? Nitronium ion (NO2+) is the electrophile that reacts with the benzene ring. WWU -- Chemistry

7. Mechanism of Aromatic Nitration (Step 2) WWU -- Chemistry

8. Mechanism of Aromatic Nitration (Step 3) WWU -- Chemistry

9. Why does the nitration reaction take place preferentially at the meta position? Let’s ask a “what if” question. WWU -- Chemistry

10. ortho BAD! meta para BAD! WWU -- Chemistry

11. meta substitution preferred because the + charge is never next to the CO2R group WWU -- Chemistry

12. Remember this mechanism for Chemistry 353! WWU -- Chemistry

13. Separation Scheme WWU -- Chemistry

14. Safety Note • Sulfuric acid and nitric acid mixed together make an especially corrosive mixture. Be sure not to get any of these acids on you. • If you do get any acid on you, immediately start flooding the affected area with lots of cold water. WWU -- Chemistry

15. Infrared Spectroscopy • Use the dry film method, described in Section 19.6, page 753. WWU -- Chemistry

16. The NO2 stretchs • N=O stretching -- 1550 and 1350 cm-1 asymmetric and symmetric stretchings, respectively • Often the 1550 cm-1 peak is stronger than the other one • Look for the conjugated C=O peak • Look for the C-O single bond stretches WWU -- Chemistry

17. ortho/para directors + + WWU -- Chemistry

18. meta directors WWU -- Chemistry

19. When you have both an o/p director and a meta director on the ring, the o/p group wins! WWU -- Chemistry

20. Green laboratory • You will prepare an iodo compound from one of the compounds listed in the procedure. • All of the compounds have activating O- groups that are ortho/para directors. • All of the compounds also have deactivating groups, but the O- groups are more powerful. WWU -- Chemistry

21. Iodination Mechanism WWU -- Chemistry

22. Reaction with I2 WWU -- Chemistry

23. Which product should you get with this reaction? WWU -- Chemistry

24. End of the Quarter • Final Examination • Tuesday, March 14th, 3:30 – 5:30 PM • Note that this is a Tuesday! • See your own instructor’s course page for study materials. • Bring your calculator WWU -- Chemistry

25. End of the Quarter • All laboratory reports, samples, etc. are due by March 9th or on the date your instructor sets. • Do not turn in samples in Erlenmeyer flasks, conical vials, or glass-stoppered bottles (they can’t be returned in time for check-out) WWU -- Chemistry

26. Laboratory Clean-Up and Check-Out • Your presence at laboratory clean-up and check-out is required. • Failure to attend will result in an automatic $15.00 non-compliance fee being added to your bill with Student Accounts. WWU -- Chemistry

27. Laboratory Clean-Up and Check-Out • There will be cleanup duties assigned by your instructor. • All of your your glassware and equipment must be cleaned for check-out. • We will personally inspect the contents of each locker, so please have all materials arranged in orderon the top of the desk, ready for check-out. WWU -- Chemistry

28. Laboratory Clean-Up and Check-Out • When you are ready to be checked out, put your name on the sign-up list. • We will inspect student lockers on a first-come, first-served basis. • If, at the time that your name comes up, you have missing items or your equipment is dirty or if you are not completely ready, your name will move to the bottom of the sign-up list. No more Mr. Nice Guy. WWU -- Chemistry

29. Laboratory Clean-Up and Check-Out • If all items are present and appropriately cleaned, we will sign off on your check-out sheet, and your check-out will be complete. • If any items are missing: you will be charged for the replacement cost. You will also receive your bill for the total of the exception items exceeding the $37.20 breakage allowance. WWU -- Chemistry

30. Laboratory Clean-Up and Check-Out • Make sure that you replace the white tape with the locker combination back onto the back of the padlocks. • We will be collecting the padlocks and replacing them with new ones. WWU -- Chemistry

31. Laboratory Clean-Up and Check-Out • All bills must be paid in full before the end of the quarter. Any outstanding bills at that time will be turned over to Student Accounts, and your registration privileges will be revoked until the bills are paid. WWU -- Chemistry

32. Clean-Up Duties • These will be announced in your individual laboratory sections. • Each island is responsible for cleaning up and returning all sample vials and stoppers. WWU -- Chemistry

33. Here is how it is supposed to work: WAIT BYE-BYE! WWU -- Chemistry

34. Final Examination • Coverage: • Experiment 6: Simple and Fractional Distillation (gas chromatography analysis methods) • Experiment 11: Isolation of Caffeine from Tea • Experiment 52: Preparation of a C-4 or C-5 Acetate Ester • Competing Nucleophiles or the Green experiment • Nitration of Methyl Benzoate or the Green lab • Don’t forget to bring your calculator! WWU -- Chemistry

35. Technique Chapters • Technique 6, Part B: Boiling Points • Technique 7, Extractions • Technique 8: Simple Distillation • Technique 15: Gas Chromatography • Technique 16: Sublimation • Appendix 3: Infrared Spectroscopy • Appendix 4: NMR Spectroscopy (not on test) WWU -- Chemistry

36. Don’t forget to bring your calculator! WWU -- Chemistry