Essay on Wittig Reaction Lab

Words: 953
Pages: 4

Makram Youssef
Chris Wong

Calculations of percent yield:

Rf values:
(literature values: trans,trans =0.36, cis,trans=0.41)

Short-wavelength TLC plate: solvent line =3.9cm filtrate: 1.4cm/3.9cm = 0.36, 1.7/3.9cm =0.44 trans,trans-isomer: 1.5cm/3.9cm = .38

Long-wavelength TLC plate: solvent line = 3.9cm filtrate: same values appear as under short-wavelength in addition to 1.1cm/3.9cm = 0.28 trans,trans-isomer: same value as under short-wavelength


This experiment was governed by the the Wittig reaction mechanism, which is done properly yields an alkene. The percent yield for the overall experimented, after purification was approximately 4.23%, not a very high yield but enough to carry out subsequent
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Since the GCMS machine was broken, we could not do tests concerning the purity of the product. Good data for the GCMS results would show quality values above 80 and ideal values would be at 99. This would show that the procedure followed for acquiring the product was followed diligently with no resulting impurities. The abundance peak of the GCMS is expected to show a high peak at a MW of 206.3g/mol since this would be consistent with the MW of our product.


We can conclude that the Wittig reaction was somewhat of a success as some desired product was obtained. The percent yield was computed to be 4.23%, which again was very low but enough to carry out our desired tests concerning the validity of the product. The experiment can of course be carried out again to promote a higher yield but just as well the objectives of the lab were completed. The TLC technique provided insight on the amalgam of products made during the reaction and the NMR tried to prove that the product was what we wished it to be. To improve, better care to make sure no impurities harm the experiment can be instituted.

Postlab questions:


2a) A ylide is a species having adjacent atoms oppositely charged. It is a carbanion that acts as a nucleophile, and adds to the carbonyl group in the first step of the mechanism.



4. A feature in the NMR