Nitration of aromatic compounds

1
Lecture 7

• Nitration of aromatic compounds
• Monday, May 22 and Wednesday, May 24

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

3
Main Reaction
This is an example of Electrophilic Aromatic
Substitution (EAS).
4
Mechanism of Aromatic NitrationStep 1 Where
does the electrophile come from?
Nitronium ion (NO2) is the electrophile that
reacts with the benzene ring.
5
Mechanism of Aromatic Nitration (Step 2)
6
Mechanism of Aromatic Nitration (Step 3)
7
Why does the nitration reaction take place
preferentially at the meta position?
Lets ask a what if question.
8
ortho
BAD!
meta
para
BAD!
9
meta substitution preferred because the charge
is never next to the CO2R group
10
Remember this mechanism for Chemistry 353!
11
Separation Scheme
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.

13
Infrared Spectroscopy

• Use the dry film method, described in Technique
  25.4, page 838.

14
The NO2 stretchs

• NO 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 CO peak
• Look for the C-O single bond stretches
• p233 Methyl m-nitrobenzoate
• p859 Nitrobenzene

15
ortho/para directors


16
meta directors
17
When you have both an o/p director and a meta
director on the ring, the o/p group wins!
18
Which product should you get with this reaction?
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.

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
  order on the top of the desk, ready for check-out.

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.

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.

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.

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.

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.

26
Here is how it is supposed to work
WAIT
BYE-BYE!
27
End of the Quarter

• Final Examination
• Thursday, June 8th, 330 530 PM
• Room SL110
• Note that this is a Thursday!
• Past Exams area in Blackboard has sample exams.
• Bring your calculator

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
  cant be returned in time for check-out)

29
Final Examination

• Coverage
• Experiment 6 Simple and Fractional
  Distillation (gas chromatography analysis
  methods)
• Experiment 12 Isolation of Caffeine from Tea
• Experiment 1356 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
• Dont forget to bring your calculator!

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)

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Dont forget to bring your calculator!