Names and ID numbers of group members (please print
legibly):
You treat E-2-buten-1,4-diol with two equivalents of PCC
(pyridinium chlorochromate) in dichloromethane solvent. After
1 hr, thin layer chromatography indicates the diol to be completely
reacted. You pour the reaction mixture into a separatory funnel
containing dichloromethane and weak aqueous acid (these two liquids
are immiscible--the intent is for the desired organic compound
to stay in the dichloromethane, while the inorganic salts go into
the water-since pyridine is a mild base, it also goes into the
aqueous acid). After shaking, you discard the aqueous acid, strip
off the dichloromethane under low vacuum, and isolate a clear,
colorless oil--in about the yield you were hoping for! You run
the same reaction with the Z isomer and isolate a different
clear, colorless oil. Strangely enough, when you take a mass spectrum
of the product from the reaction of the E isomer, it has
a mass of 84, but the product from the Z isomer has a mass
of 102 (in each case these are the true molecular ions--no funny
fragmentations going on here).
You make up NMR and IR samples of both products, but forget to
label which is which. Your NMR and your IR instruments both break
after running only one sample (you are having a seriously bad
day . . . ) The two spectra you managed to get are attached at
back--you're pretty certain one is for one product, and one is
for the other.
Draw the two products here and label which product comes from which educt:
To which of the two products does the provided NMR spectrum belong?
Briefly describe the NMR spectrum expected for the other
product (in particular, the rough chemical shift for each unique
chemical environment and the coupling pattern for each signal--you
may sketch your answer if you can do it neatly).
To which of the two products does the provided IR spectrum belong? Briefly describe the IR spectrum expected for the other product (i.e., approximately where will peaks occur that provide information about functional groups? e.g., if a nitrile were the expected product, you might say "medium intensity peak 2200 cm-1 corresponding to C-N triple bond stretch"-don't worry about the fingerprint region below 1500 cm-1, but try to roughly describe every peak above 1500 cm-1--again, a sketch is OK if it is neat and clearly labeled).
Draw a mechanism for the process whereby an intermediate product from the Z isomer picks up an "extra" mass of 18 (by comparison to the E isomer) so as to form the isolated product.
