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Wittig Reaction Lab

In: Science

Submitted By makyou
Words 946
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

Discussion:

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 procedures to check for the validity of the product.
The first of these tests was involved TLC (Thin Layer Chromatography) and was used to assess the presence of the product intended as well as the products of the filtrate, or byproducts. It should be noted that the developing solution used for this test was Hexane and that the plate of product and filtrate was analyzed under both long and short wavelength UV lights. Under these lights, the filtrate showed brighter than the spotted product giving off a pinkish hue. It should also be noted that the filtrate filtrate contained triphenylphosphine oxide, the minor cis, trans-isomer, and some trans,trans product. In order of increasing Rf values, it was expected that triphenylphosphine oxide would be lower than the trans,trans-diene, which would be lower than the cis,trans-diene. In the short wavelength TLC plate, the filtrate had two spots with the Rf values of 0.36 and 0.44 respectively as shown above. The product spot had an Rf value of .38. Under the long-wavelength UV light, the TLC plate showed the same spots as under the short-wavelength light with the exception of one spot for the...

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