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Steam Distillation – Oil of Cloves

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1 Steam Distillation – Oil of Cloves

2 PT = NAP˚A +NBP˚B + NCP˚C + … (1)
Distillations: Steam Distillation Steam distillation arises from an interesting curiosity of immiscible systems The distillation of liquids that are fully miscible is governed by Raoult’s Law PT = NAP˚A +NBP˚B + NCP˚C + … (1) The mixture will have its own unique boiling point The contribution of each component to the vapor phase is related to its partial vapor pressure and mole fraction 3. In the distillation of immiscible liquids, the two act as two separate liquids A B

3 5. The mixture will boil at a temperature
Distillations: Steam Distillation The total vapor pressure above an immiscible system is equal to the sum of the vapor pressures independent of their relative amounts PT = P˚A + P˚B + P˚C + … (2) 5. The mixture will boil at a temperature typically lower than either liquid 6. Consider a mixture of iodobenzene and water: At 98 oC the value of each vapor pressure is: 46 torr + 714 torr = torr Mixture boils!

4 Distillations: Steam Distillation 7. The mole fraction of each component (nA and nB) in the vapor phase is given by the ratio of its partial pressure over the total pressure: nA = P˚A/PT (3) and nB = P˚B/PT (4) 8. If the vapor is condensed, the resulting distillate has the same composition. The ratio of the mole fractions for A and B in the distillate is then given by Equation 5, which results from dividing equation 3 by equation 4: nA/nB = P˚A/P˚B (5) Thus in the case of the steam distillation of iodobenzene and water, the vapor phase, iodobenzene would only have a mole fraction of (46 torr/714 torr) But because it has a larger molecular weight (204 vs. 18 grams per mole) about 0.7 grams of iodobenzene are collected for every gram of water In the gas phase the two are fully miscible, but once the vapor condenses – the two are no longer miscible – and can be physically separated

5 Distillations: Steam Distillation B. Uses/Apparatus
This method is typically used to extract the volatile components of plants for use in perfumery, flavors or aromatherapy products. Steam distillation is used in the industries that produce these products as well as amateur set-ups like this one

6 Isolation of Natural Products
This isolation of a “natural product” from its native matrix is one of the oldest examples of applied organic chemistry – medicines and herbal remedies prepared by early human civilizations are good examples of this This field undergoing explosive growth as we attempt to find interesting molecules in nature that can be used for medicinal purposes as well as for flavorings, dyes and cosmetics from a natural rather than synthetic source The American Chemical Society (ACS) publishes a Journal that covers recent developments in this highly interesting and important field Papers start with the isolation of the animal or plant from it’s native environment followed by the various separation and identification techniques used to identify each component Recently, the initial assays of the anti-microbial, anti-carcinogenic and toxicity behavior of each component are also reported

7 When these isolations are for medicinal purposes, the field is known as Pharmacognosy
"Pharmacognosy" derives from two Greek words, "pharmakon" or drug, and "gnosis" or knowledge. Like many contemporary fields of science, pharma-cognosy has undergone significant change in recent years and today represents a highly interdisciplinary science which is one of five major areas of pharmaceutical education. Its scope includes the study of the physical, chemical, biochemical and biological properties of drugs, drug substances, or potential drugs or drug substances of natural origin as well as the search for new drugs from natural sources. Research problems in pharmacognosy include studies in the areas of phytochemistry, microbial chemistry, biosynthesis, biotransformation, chemotaxonomy, and other biological and chemical sciences.

8 In today's experiment we will isolate oil of cloves from cloves (Eugenia caryophyllata). Cloves have been used as a flavoring agent for food for thousands of years. In addition, oil of cloves was one of the first know dental pain killers...a few drops of oil of cloves will numb the pain of a tooth ache. One formulation sold on the market for tooth pain relief still contains oil of cloves. Oil of cloves is rich in eugenol (4-allyl-2-methoxyphenol) and contains a trace amount of caryophphyllene.

9 Steam Distillation of an Essential Oil
We will be using a modification of the distillation apparatus in the text

10 Steam Distillation of an Essential Oil
The liquid will be transferred to a large separatory funnel and extracted with methlyene chloride CH2Cl2 The essential oil extract is soluble in methlyene chloride, not water – So draining the lower methylene chloride layer, and evaporating the methylene chloride, will afford the extracted oil – H2O CH2Cl2

11 Steam Distillation of an Essential Oil
The methylene chloride extract will be dried by passing it through a disposable pipette filled with anhydrous Na2SO4 drying agent – you will obtain a weight of the material (it won’t be much) and calculate a % recovery based on the original mass of plant material

12 Steam Distillation of an Essential Oil
qualitatively – to determine which components are in the oil We will analyze the essential oil by gas chromatography… and quantitatively to determine the relative amounts of each component

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