Exercise 3: SIMPLE DISTILLATION AND STEAM DISTILLATION

Volatility

Relative ease by which a substance changes from the liquid to gaseous (vapor) state

Requires energy to break away from other molecules in the liquid & maintain the vigorous movement characteristic of gaseous particles

What does an individual molecule escaping from the liquid into the gaseous state require?

Vapor pressure

The amount of substance that is present as a gas in the space above the surface of the liquid contained in a closed vessel

Equilibrium vapor pressure

Dependent on the external pressure of the system and increase with temperature

Direct relationship

Equilibrium vapor pressure & temperature

Evaporation/ slow volatilization

The escape of surface molecules of a given liquid into the air.

Rapid Volatilization

Boiling is what type of volatilization

Turbulence

Boiling is rapid volatilization that may be accompanied by what?

Due to vapor formation even in the bulk of the liquid

Why does turbulence accompany boiling?

Vapor pressure (Pv) = external applied pressure (Pext)

When does boiling occur?

boiling point

Temperature of Pv = Pext

Pure liquids

Boiling point is a characteristic property of which specific liquids?

Indirect relationship

Relationship of volatility of liquid and its boiling point

the higher its boiling point

The less volatile the liquid is, _____

Pure liquid

It has a sharp boiling point.

Because a uniform amount of energy is required to disrupt the intermolecular forces of attraction among its molecules

Why does pure liquids have a sharp boiling point?

Pure liquid

It requires a uniform amount of energy to disrupt the intermolecular forces of attraction among its molecules.

Temperature (in pure liquid)

Remains constant until all the liquid has boiled off, leaving no residue

atmospheric pressure

Boiling points may vary due to fluctuations in _____

Simple distillation

Boiling point is usually determined through ___ when sufficient quantities of the sample are available.

Distillation

The process of vaporizing a liquid and then converting the vapor to the liquid state by subsequent cooling

Subsequent cooling

Distillation occurs when a liquid is vaporized then converted from vapor to liquid state by ____.

Distillate

Sample is heated t sustain boiling then the vapor is allowed to pass through a cooling tube to condense to form ___

Liquid will have a sharp boiling point * impurities will remain behind when the liquid has evaporated

What happens when the sample contains nonvolatile impurities after forming the distillate?

Distillation

Serves to separate the volatile from the nonvolatile components of a mixture

Distillation

Employed when the removal of a volatile solvent from a substance that is being purified is desired

In removal of a volatile solvent from a substance that is being purified

When is distillation also happen employed?

Distilling flask (usually a round-bottom flask), a thermometer, a condenser, a receiver

Basic parts of a distillation setup

Easy

Is a distillation setup easy to assemble?

Distilling flask

In distillation setup, what is fitted to a water condenser?

Adapter

It is fitted to the condenser so that the distillate may be collected in a suitable receiver.

Placed where the tip of the bulb is in the center of the flak's neck & about 5 mm below the sidearm leading to the condenser

How is a thermometer positioned?

5 mm below

Tip of the bulb of the thermometer must be ___ mm below the sidearm leading to the condenser

Boiling chips

It is placed in the distilling flask to prevent bumping.

No more than two-thirds of its maximum volume

Flask is filled with how much volume, then heated to boiling.

Boiling flask must NOT BE ALLOWED TO RUN DRY.

Can the boiling flask be allowed to run dry?

A few drops of liquid should remain in the flask at the end of the distillation process.

How many drops of liquid should remain in the flask at the end of the distillation process?

Steam distillation

used to separate slightly volatile water- insoluble substances from nonvolatile materials

1. When a relatively small amount of volatile materials is available

2. In extracting substances that decompose at high temperature

When is steam distillation especially useful?

Only applies if organic substance is insoluble in water and has a boiling point much higher than 100º C

Principle of steam distillation applies in where?

Components exert its own vapor pressure independent of the other

Example 1 Fact

Total vapor pressure of two components equal to the sum of the individual vapor pressures

Example 2 Fact

The mixture must distill at this lower temperature

What happens if

Total pressure = atmospheric pressure at a temperature below the boiling point of either pure substances

The mixture boils at a temperature lower than the boiling point of either one of the mixture

If:

Mixtures distill together because the mixture will exert a vapor pressure equal to the atmospheric pressure, then:

Essential oils

Substances that give the characteristic odor and flavor of plants, flowers, and fruits

> high-boiling liquids

> insoluble in water

> isolated from the plant material by steam distillation

Essential oils

Steam distillation

How are essential oils isolated from the plant material?

> Not a pure chemical compound

> Mixture of several types of organic compounds

Characteristics of essential oils

Monoterpened

Most prominent compounds of essential oils

> Geraniol (rose oil)

> Linalool (ilang-ilang oil)

> Citral (lemongrass oil)

> Limonene (oil of lemon and orange)

Examples of monoterpenes