Chemistry 3302 S98 Section 1

Second Group Learning Project

(due 5/26/97 in class)

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.