Nitration and Iodination of aromatic compounds

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Lecture 7

• Nitration and Iodination of aromatic compounds

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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.

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Nitration of Methyl Benzoate

• Brown laboratories
• Experiment 40

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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

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

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Infrared Spectroscopy

• Use the dry film method, described in Section
  19.6, page 753.

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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

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ortho/para directors


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

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Iodination Mechanism
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Reaction with I2
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Which product should you get with this reaction?
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End of the Quarter

• Final Examination
• Tuesday, March 14th, 330 530 PM
• Note that this is a Tuesday!
• See your own instructors course page for study
  materials.
• Bring your calculator

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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
  cant be returned in time for check-out)

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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Here is how it is supposed to work
WAIT
BYE-BYE!
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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
• Dont forget to bring your calculator!

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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)

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Dont forget to bring your calculator!