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Spearmint Leaves Lab Report

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Steam Distillation of (S)-(+)-Carvone from Caraway Seeds and (R)-(-)-Carvone from Spearmint Leaves. Analysis of Products by Infrared Spectroscope and TLC

Methods/Backgrounds:
In this experiment we had to isolate (S)-(+)-Carvone from Caraway Seeds and (R)-(-)-Carvone from Spearmint leaves via steam distillation and by extracting
the distillate with CH2Cl2. We analyzed the samples/enantiomers by using infrared spectroscopy, Bayer test, and TLC.
In the liquid phase, the molecules are constantly in motion, and some of them at the top escape to vapor phase. A dynamic equilibrium is when the number of gas molecules exiting/entering the liquid phase is in equilibrium. The liquid vapor pressure is the pressure gas molecules push against the walls …show more content…

These two compounds have the same bp, mp, densities, color, viscosity, infrared spectra, TLC and gas chromatography, so the only way to differentiate them is by its polarimetry and scent. The (R)-(- )-Carvone smells like spearmint and is found in spearmint oil which also contains minor amount of limonene. Comparatively, (S)-(+)-carvone is found in caraway seeds and also contains limonene. Both of these enantiomers are not natural nor readily available. However, via distillation they can be isolated.
Distillation is a technique used for separating, identifying and purifying liquids. Simple Distillation and fractional distillation are often used for isolation of mixture of liquids. In this experiment, steam distillation is used to separate carvone from caraway seeds and spearmint leaves. For steam distillation, the bp has to be less than 100° C, compound mixed with water has to be stable at 100° C.The principles of steam distillation focus on Raoult’s law and Dalton’s law. However, since it is not soluble in water, it does not depend on its mole fraction in the mixture. Therefore, Raoult’s law does not apply to steam distillation because the compounds are immiscible, so they do not depend on each other’s mole fraction. According to Dalton’s law total vapor pressure is higher than most volatile component and boiling point mixture is lower …show more content…

The resulting spots from all three samples traveled about same distance. There
were three big spots muddy brown in color. Out of the three main muddy spots, there were
also some yellowish spots observed for the spearmint leaves extraction sample and co-spot mixture sample. Knowing that both of the enantiomers contain Limonene, these yellowish spots probably indicate presence of Limonene. The location of the spots indicates the affinity of the compound to specific phase. The muddy spots observed were close to each other at similar distance from the baseline. This indicates that the compounds were less polar and had greater affinity to the mobile phase and quickly moved up the plate with larger retention factors. Also, more polar compounds in the sample have greater affinity to the stationary phase and therefore move slowly with smaller retention factors. This findings suggest that Carvones are less polar compared to limonene, which is somewhat more polar because it was found in the middle of baseline and muddy spots. This reasoning is supported by the calculated retentions factor. The Rf for the Spearmint leaves for the three samples were calculated to be: pure (R)-Carvone

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