Experiment Of A Wittig Reaction

The purpose of this experiment was to perform a Wittig reaction using two different methods: In method I, 250 mg aldehyde was mixed with 785 mg phosphonium salt in 5 M NaOH solvent. This mixture was stirred for thirty minutes and filter by vacuum filtration for the product. In method 2, 250 mg of aldehyde, 785 mg, benzyltriphenylphosphonium chloride, and 380 mg potassium phosphate tribasic were homogenize with a pestle and mortar. Vacuum filtration was also used in this method to attain the product. The products in both methods were used for recrystallization and TLC. For recrystallization, boiling ethanol was used as the solvent. In the TLC procedure, 90/10 hexane and ethyl acetate was used. NMR was collected for products used in these methods.

In this experiment, method 1 generate a mixture of yellowish crystals and a yellowish gluey product. Using method 2, the product appear as white crystals. Given that the yellow color remain throughout the product in method 2, too much aldehyde was added. It was predicted that this was the source of error because aldehyde was a yellow liquid. In this experiment, 293 mg of aldehyde was weighted for method 1 instead of 250 mg and. Although .7906 mg of phosphonium salt was added, this probably was not enough to complete the reaction. The only significant change throughout method was 1 was that the yellowish mixture became slightly lighter. However, it was found that after vacuum filtration, there was some white and yellow