Steam Distillation

Steam Distillation

Purpose: To use steam distillation to purify heat sensitive, natural products, like essential oils.

Procedure

Please refer to:

Williamson, Macroscale &Microscale Organic Experiments 4th Ed., pgs.98-109

Results

Table 1.1: Steam distillation

Drop # (every third drop) Temperature (ºC) Addition of 0.5 mL water

1 100.3 Water added

2 100.5

3 100.5 Water added

4 100.6 Water added

5 100.6

6 100.6 Water added

7 100.6

8 100.6 Water added

9 100.3

10 100.6

Observations: The residue was cloudy during distillation. This indicated that it was wet. The water was added when the solution appeared to be getting low in volume.

Table 1.2: Recovery of organic material

Object being weighed Weight in grams

Weight of empty, clean test tube 6.446 g

Weight of clean test tube with spearmint oil 6.635 g

Weight of spearmint oil 0.189 g

Table 1.3: IR Spectroscopy

Frequency Corresponding Functional Group

3083.81 C-H

2923.91 C-H

1674.33 C=O

Conclusion

In this experiment, the process of steam distillation was used to purify a natural product, (the essential oil of spearmint). This phenomenon works because when two immiscible liquids are distilled, the boiling point of the mixture is below the boiling point of the both pure compounds. Since water has a significantly lower boiling point than spearmint, a much greater proportion of water molecules was vaporizing at any time during the distillation. Even though the components of spearmint oil have low vapor pressure, they are volatile enough to vaporize to some extent and a small amount will lifted off with the water molecules. This boiling will occur when the independent internal vapor pressures are equal to 760 torr, which is the external vapor pressure. It is noted that steam distillation, unlike regular distillation, it does not follow Raoult’s Law.

After steam distillation was completed, the essential oil was recovered and a thin layer chromatography was conducted. When this TLC was conducted, there was one spot of pure essential oil and one of the distilled and recovered essential oil. The results indicated that the distilled, recovered oil was pure because it came out as a single spot, level with that of the pure oil. The infrared spectroscopy was performed next. IR spectroscopy is used to identify the functional by stretching and bonding frequencies of bonds. The peaks correspond to the functional groups.