Description
Lab 7. Halohydrin formation
For this assignment, the target compound that you should synthesize is ___________________________.
Again, this is an electrophilic alkene addition reaction. Examine the product to determine the location of
the new functionality. Keep in mind the bromonium ion intermediate and the consequences of its
structure. The nucleophile again attacks at the more substituted position.
Synthesis Procedures
1. Start Virtual ChemLab and select Halohydrin Formation – 1 from the list of assignments on the
whiteboard. After entering the synthesis laboratory use the available reagents on the stockroom
shelf, identify the appropriate starting materials required to synthesize the target compound and
add them to the round bottom flask. Now add ether (Et2O) as a solvent and drag the flask to the
Stir Plate on the lab bench.
2. The round bottom flask containing the starting materials should now be on the stir plate, and the
contents of the flask should be visible on the chalkboard. From the group of reagents found on the
lab bench, select the correct reagent to synthesize the target compound and add it to the flask on
the stir plate. Now attach the heater, condenser, and N2 gas to the round bottom flask so the
reaction mixture can be heated.
3. Start the reaction by clicking on the Stir button on the front of the stir plate. You should be able to
observe the reaction mixture stirring in the flask. Monitor the progress of the reaction using TLC
measurements as necessary until the product has formed and the starting materials have been
consumed. You can advance the laboratory time using the clock on the wall. With the electronic
lab book open (click on the lab book on the stockroom counter), you can also save your TLC
plates by clicking Save on the TLC window.
4. When the reaction is complete, “work up” your reaction by first dragging and dropping the
separatory funnel on the flask and then adding H2O to the funnel. Extract the organic layer in the
funnel by clicking on the top layer and dragging it to the cork ring on the lab bench. Your target
compound should now be in this flask.
List the starting materials, solvent, reagent, and products formed: _________________________
______________________________________________________________________________
How long did it take to finish the reaction? ___________________________________________
What are the TLC values (Rf) for (a) Starting Materials:__________ (b) Products: ____________
Write a reaction(s) and mechanism(s) for this reaction:
Lab 7. Halohydrin formation
FTIR and MS Spectra
After completing a reaction and working up the products, it is still necessary to confirm that the correct
product was formed. The most common tools used for this analysis are Fourier Transform Infrared (FTIR)
and Mass spectroscopy (MS). Details on interpreting FTIR and MS spectra are found in your textbook.
Your instructor may or may not ask you to perform this section depending on how your class is
structured.
5. To collect an FTIR spectrum of your unknown, click on the FTIR spectrometer located to the left
of the lab bench and drag the salt plate icon to the flask on the lab bench. A window containing
the FTIR spectrum for your product should now open. Identify the relevant peaks in the FTIR
spectrum and record the position and associated functional group for each in the FTIR table
below. The FTIR spectrum can also be saved to the lab book for later analysis.
Table #: FTIR of (name of compound)
FTIR List position (cm-1) & functional group
1.
2.
3.
4.
5.
6.
Etc.
6. To collect an MS spectrum of your unknown, click on the MS spectrometer located to the left of
the lab bench and drag the sample vial to the flask on the lab bench. A window containing the MS
spectrum for your product should now open. Identify the relevant peaks in the MS spectrum and
record the M/Z and associated fragmentation group for each in the MS table below. The MS
spectrum can also be saved to the lab book for later analysis.
Table #: MS of (name of compound)
m/z Peak value & fragmentation group
1.
2.
3.
4.
5.
6.
Etc.
7. Do the FTIR and NMR spectra you measured and recorded in the tables above confirm that you
synthesized the assigned target compound? Explain. ___________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
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