Lecture 7

1. Lecture 7 Nitration of aromatic compounds Monday, May 22 and Wednesday, May 24 WWU -- Chemistry

2. Reading Assignment • pp. 228 – 232 (Experiment 28) • Techniques 5, 6, 7 • Technique 25, p. 833-838 • NOTE: We will use the “dry film” method, described on page 838 • Chapter 22 from the lecture textbook WWU -- Chemistry

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

4. 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

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

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

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

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

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

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

11. Separation Scheme WWU -- Chemistry

12. 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

13. Infrared Spectroscopy • Use the dry film method, described in Technique 25.4, page 838. WWU -- Chemistry

14. 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 • p233 Methyl m-nitrobenzoate • p859 Nitrobenzene WWU -- Chemistry

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

16. meta directors WWU -- Chemistry

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

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

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

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

27. End of the Quarter • Final Examination • Thursday, June 8th, 3:30 – 5:30 PM • Room: SL110 • Note that this is a Thursday! • Past Exams area in Blackboard has sample exams. • Bring your calculator WWU -- Chemistry

28. End of the Quarter • All laboratory reports, samples, etc. are due by June 8th 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

29. Final Examination • Coverage: • Experiment 6: Simple and Fractional Distillation (gas chromatography analysis methods) • Experiment 12: Isolation of Caffeine from Tea • Experiment 13&56: Preparation of a C-4 or C-5 Acetate Ester • Experiment 15: Spearmint and Caraway Oil • Experiment 21: Competing Nucleophiles • Experiment 28: Nitration of Methyl Benzoate • Don’t forget to bring your calculator! WWU -- Chemistry

30. Technique Chapters • Technique 12: Extractions • Technique 13: Boiling Points and Density • Technique 14: Simple Distillation • Technique 17: Sublimation • Technique 22: Gas Chromatography • Technique 25: Infrared Spectroscopy • Technique 26 & 27: NMR Spectroscopy (not on test) WWU -- Chemistry

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