Lab Report: Limonene Extraction Experiment – Brandon Skenandore
Total word count: 343
Time spent researching and writing: 2 hrs
Limonene Extraction Experiment
The purpose of this lab experiment was to extract R-limonene from orange peels using steam distillation, a separatory funnel, and rotary evaporation. This limonene extract was then observed and analyzed using GC/MS and polarimetry. The orange peel initially smelled good, like citrus. The diethyl ether contrasted with the sweet smell, producing a pungent odor. After the steam distillation, the distilled mixture still smelled bad, and there were two layers. The separatory funnel was then used and once the organic layer was collected, the extraction was obtained from the ether using a rotovap. The final solution was a yellowy, oily, pungent extract that was assumed to be the limonene.
Once this was collected, an automatic polarimeter was used to find the observed rotation and then a calculation was performed to find the specific rotation of both the pure oil and the extracted oil. See notebook pages for the calculations. Our observed rotation for the polarimeter was .2259º. The specific rotation was then 2.237º. The pure extract’s observed rotation was 8.9303º. The specific rotation of the pure extract was 89.303º. The calculated optical purity for the experimental and pure compound was therefore 1.945% and 77.65%, respectively. The optical purity of the experimental value was very low. One reason for this could be because there may have been some diethyl ether left over in the mixture, which lowered the rotation level. Another reason could be because the entire row’s extract was combined, and because of this different results could have been caused. Either way, this was a very large discrepancy.
The specific rotation of the pure oil compared to the literature value was 89.303º vs 115º. This is also a large discrepancy, but since the literature value is of pure limonene and the experimental was of orange oil, there could have been other compounds in the orange oil that were optically active, thus changing the optical rotation of the overall compound.