a. Volatile oils/ Hydrocarbon volatile oils

Question 1

What are volatile oils?

Answer 1

Volatile oils are the odorous principles found in various plant parts because they evaporate when exposed to air at ordinary temperatures they are called volatile oils and ethereal oils.

Volatile or essential oils, as their name implies, are volatile in steam.

Question 2

What are essential oils?

Answer 2

Volatile oils also represent the essences of odoriferous constituents of plants so they are also called as essential oils.

Question 3

Where is the difference between fixed and volatile oils?

Answer 3

Volatile Oils differ entirely in both chemical and physical properties from fixed oil.
1. Volatile oils can be distilled from their natural sources;
2. They do not consist of glyceryl esters of fatty acids. Hence, they do not leave a permanent grease spot on paper
3. And cannot be saponified with alkalis.
4. Volatile oils do not become rancid as do the fixed oils, but instead, on exposure to light and air, they oxidize and resinify.

Question 4

What are the sources of volatile oils?

Answer 4

They may occur in:
1. Specialized secretory structures such as glandular hairs (Labiatae)
2. Modified parenchymal cells (Piperacea)
3. Oil tubes called vittae (Umbelliferacea)
4. They may be formed directly by the protoplasm
5. By hydrolysis of certain glycosides (bitter almond oil)
6. In conifers, volatile oils occur in all tissues

Question 5

What are some physical properties?

Answer 5

Volatile oils differ greatly in their chemical constitution, they have a number of physical properties in common.
1. They possess characteristic odors.
2. They are characterized by high refractive indices.
3. Most of them are optically active.
4. As a rule, volatile oils are immiscible with water but they are sufficiently soluble to impart odor to water. Aromatic waters depend on this slight solubility.
5. Their density is generally lower than that of water.

Question 6

What is the composition of volatile oils?

Answer 6

Volatile oils are generally mixtures of hydrocarbons and oxygenated compounds derived from these hydrocarbons.

In some oils (e.g. oil of turpentine) the hydrocarbons predominate and only limited amounts of oxygenated constituents are present; in others (e.g. oil of cloves) the bulk of the oil consists of oxygenated compounds.

Question 7

How is the odor and taste of volatile oils determined?

Answer 7

The odour and taste of volatile oils is mainly determined by these oxygenated constituents, which are to some extent soluble in water but more soluble in alcohol.

Volatile oils contain over 200 constituents and only a trace amount of constituents are essential for odor and flavor.

Question 8

How are volatile oils classified?

Answer 8

The volatile oils may be classified on the basis of their biosynthetic pathway as:
1. Terpene derivatives
2. Aromatic compounds

Question 9

What are Terpene derivatives?

Answer 9

They are formed via the acetate mevalonic pathway. Eg: Peppermint and caraway oil.

Question 10

What are aromatic compounds?

Answer 10

They are formed via the shikimic acid methyl propanoid pathway. Eg Cinnamon and Clove Oil.

Question 11

What is the classification of volatile oils?

Answer 11

Usually volatile oils are classified according to the type of organic compounds present in them. They may be:
1. Hydrocarbon
2. Alcohol
3. Aldehyde
4. Ketone
5. Phenol
6. Ester
7. Ether
8. Peroxide

Question 12

Hydrocarbon volatile oils?

Answer 12

Terpentine oil

Question 13

Alcohol volatile oils?

Answer 13

Coriander Oil, Cardamom Oil

Question 14

Aldehyde volatile oils?

Answer 14

Cinnamon Oil , Lemon Oil

Question 15

Ketone volatile oils?

Answer 15

Caraway Oil ,Spearmint Oil

Question 16

Phenol volatile oils?

Answer 16

Clove Oil , Thyme Oil

Question 17

Ester volatile oils?

Answer 17

Lavender Oil

Question 18

Ether volatile oils?

Answer 18

Nutmeg Oil and Anise Oil

Question 19

Peroxides volatile oils?

Answer 19

Chenopodium Oil

Question 20

Define distillation of volatile oils?

Answer 20

The method of distillation depends upon the type of plant material. Three types of distillation is used that is water, steam and water and direct steam distillation.

The volatile oils from fresh materials are separated by hydro distillation, and volatile oils from air dried parts are separated by steam distillation. However it is better to use fresh materials in either case.

Question 21

What is enzymatic hydrolysis of volatile oils?

Answer 21

Glyosidic volatile oils (mustard oil) are obtained by enzymatic hydrolysis of the glycosides. In black mustard seeds, the glycoside, sinigrin, is hydrolyzed by myrosin with the production of volatile mustard oil.

Question 22

Define expression of volatile oils?

Answer 22

Some volatile oils cannot be distilled without decomposition and are usually obtained by expression (lemon oil, orange oil) or possibly by other mechanical means.

Question 23

What is enfleurage?

Answer 23

For extraction of oils used in perfumery.

Question 24

What are hydrocarbon volatile oils?

Answer 24

Hydrocarbons occur in practically all volatile oils. Limonene is probably the most widely distributed of the monocyclic terpenes. It occurs in citrus.
A volatile oil drug composed chiefly of hydrocarbons is turpentine oil.

Question 25

What is turpentine oil?

Answer 25

Turpentine oil or spirits of turpentine is the volatile oil distilled from the oleoresin obtained from Pinus plaustris and from other species of Pinus Linné (Fam. Pinaceae) that yield terpene oils exclusively.

Question 26

Explain the collection and preparation of volatile oils.

Answer 26

The oleoresins which are collected are transferred to copper stills, water is added and heated. The impurities like woody debris, sand, and other particles float on the surface of water which is skimmed off. The clarified resin is then subjected to distillation for obtaining the oil. The oil obtained is then treated with aqueous solution of sodium hydroxide. The treatment with sodium hydroxide removes the traces of phenols, cresol, and resin acids. This oil which is produced is called the rectified turpentine oil.

Question 27

What are the properties/characteristics of turpentine oil?

Answer 27

Turpentine oil is a colorless to slightly yellowish transparent liquid with a strong characteristic odor and bitter, pungent taste. It is soluble in alcohol, insoluble in water and miscible with glacial acetic acid, ether, chloroform, and fixed oil. Turpentine oil should be stored in air-tight containers and in a cool place.

Question 28

What are the uses of turpentine oil?

Answer 28

1. Turpentine oil is used as counterirritant, rubefacient, in swelling, neuralgia, as mild antiseptic, as an expectorant in chronic bronchitis, as diuretic, and urinary antiseptic.
2. When taken internally it causes irritation of kidney also.
3. In industries it is used in the preparation of disinfectants, insecticides, paints, varnishes, and pine oil.