Safe Use of Organic Substances (HSC SSCE Chemistry): Revision Notes

Safe Use of Organic Substances

Introduction

Organic compounds play an important role in chemistry and industry, but they also present significant safety challenges. Understanding how to work safely with these substances is essential for both laboratory work and industrial applications.

Alkenes and alkynes contain double and triple bonds that make them highly reactive. They can undergo reactions with halogens, water, and hydrogen. Alkanes are less reactive but still undergo combustion and substitution reactions. When these organic chemicals are used in reactions, they can create various hazards that need to be carefully managed.

Using organic substances safely

Organic substances in laboratories and industry

In high school chemistry laboratories, you will encounter small amounts of organic substances that present manageable risks. However, in industrial settings, these same chemicals are used in much larger quantities, which creates greater challenges for risk management and safe handling.

Common products that contain potentially dangerous organic substances include:

• Paints and lacquers
• Adhesives and glues
• Degreasing materials
• Dry cleaning chemicals
• Printing materials

These everyday products often contain organic substances such as:

• Ethanal (acetaldehyde)
• Propanone (acetone)
• Pentyl acetate
• Benzene
• Tetrachloromethane (carbon tetrachloride)
• Dichloromethane
• Ethanol
• 1,2-ethanediol

Common hazardous organic substances

The table below shows some widely used organic solvents, their names, industrial uses, and associated health hazards.

IUPAC name	Other common names	Uses	Hazards
Ethanal	Acetaldehyde, acetic aldehyde, ethyl aldehyde	Polymer production, perfume production	Inhaled vapours are toxic. Long-term exposure can cause nervous system damage and pulmonary oedema. Short-term irritant to skin, eyes and mucous membranes.
Benzene	Coal naphtha, mineral naphtha, pyrobenzol	Production of plastics, resins, synthetic fibres, dyes, detergents, medicines and pesticides	Inhaled vapours are toxic. Long-term exposure can cause nervous system damage. Is an anaesthetic. Causes damage to blood components, anaemia and bleeding.
Propanone	Acetone, dimethyl ketone, methyl ketone, dimethylformaldehyde	Used as nail polish remover and paint thinner	Inhalation of vapours causes irritation to eyes, nose and throat. Not harmful if ingested.
Tetrachloromethane	Carbon tetrachloride, perchloromethane	Used in dry cleaning, as a degreaser, in fire extinguishers and as a pesticide	Toxic by inhalation, absorption or ingestion. Causes nervous system damage, irritates eyes and skin. Long-term skin contact causes dermatitis, and long-term liver and kidney damage.

The challenge of chemical naming

One significant safety challenge is that organic compounds often have multiple names. Many industries and laboratories use common names that don't describe the chemical structure. For example, benzene might be called "coal naphtha" or "mineral naphtha." From these alternative names alone, it's difficult to identify that the substance contains benzene and therefore requires appropriate safety precautions.

Safety Data Sheets (SDS)

To reduce confusion about chemical names and improve safety, Safety Data Sheets (SDS) are used. An SDS is a document that provides comprehensive safety information about a chemical substance.

Every chemical has an SDS. These documents are:

• Available online
• Kept in all chemical laboratories
• Maintained at manufacturing and industrial sites that use chemicals

Chemical labeling

Another important method of preventing accidental contact with hazardous chemicals is proper labeling. Chemical labels must clearly indicate:

• The name of the chemical
• The concentration
• Possible hazards (using standardized warning symbols)

Proper labeling procedures are covered by local regulations to ensure consistency and safety across all settings.

Risks of organic chemicals related to physical properties

Understanding the physical properties of organic compounds helps us identify safe ways to use them. Three key properties create particular hazards: volatility, flammability, and reactivity.

Volatility

Many organic compounds are volatile, meaning they have weak intermolecular forces and evaporate easily at room temperature to form vapour.

Important characteristics of organic vapours:

• Can be less dense than air (will rise and fill the room)
• Can be denser than air (will settle at lower levels)
• Usually colourless and therefore not easily visible
• Almost all have pungent (strong) smells, making them detectable

Flammability and flashpoint

Most organic compounds are highly flammable, especially when in vapour form. This hazard is related to a property called flashpoint.

Flashpoint is the lowest temperature at which a liquid can form an ignitable mixture in air near the surface of the liquid.

Key points about flashpoint:

• The lower the flashpoint, the easier it is to ignite the substance
• Any organic substance with a flashpoint below $23\degree\text{C}$ is considered highly flammable
• Chemicals with flashpoints below $23\degree\text{C}$ include cyclohexane, cyclohexene, ethanol, propanone, pentane, propanol, and methanol

Reactivity

Many organic compounds are highly reactive and will readily react with:

• Substances in the air
• Water
• Other nearby chemicals

This reactivity increases the risk of unexpected or dangerous reactions occurring if chemicals are not stored and handled properly.

Exposure methods and effects

There are three main ways that organic compounds can enter the human body, each with different mechanisms and risks.

Routes of exposure

1. Inhalation through the lungs

This is the most common exposure method because:

• Vapours are the easiest form of chemical to encounter
• Gases can be breathed in without being noticed
• The organic compound dissolves into the bloodstream through the lung walls
• It then travels around the body to various internal organs where it accumulates over time

2. Absorption through the skin

This method is less common but uses the same mechanism as inhalation:

• Compounds dissolve through the skin
• They make their way into the bloodstream
• They then travel to internal organs

3. Ingestion (swallowing)

This usually happens accidentally when:

• Chemicals remain on hands or clothes
• They are later ingested along with food or drinks
• They enter the digestive system and are absorbed

Effects of exposure

The effects of contact with organic compounds vary depending on:

• Length of exposure
• Type of chemical
• Health of the person exposed

Contact effects (absorption through skin)

When organic solvents contact the skin, they dissolve the fats that form the protective barrier. This allows chemicals to enter the bloodstream more easily.

Symptoms of skin contact include:

• Burning or tingling sensation
• Presence of welts or rashes
• Chemical burns (similar to burns from heat or flame)

Acute poisoning

Acute poisoning occurs immediately upon contact or develops within a few hours. This often happens upon exposure to organic vapours.

Chronic poisoning

Chronic poisoning occurs after repeated exposure, often over years or decades. This is commonly found in industries where workers are exposed to chemicals daily.

Prevention methods

Various methods are used in laboratories and industry to prevent or minimise exposure to organic compounds. These can be remembered using the acronym SIV: Substitution, Isolation, Ventilation.

Substitution and elimination

Many industries have moved to eliminate or substitute harmful chemicals with safer alternatives.

Isolation

Isolation means creating physical separation between people and chemicals. This can be achieved at different scales:

Simple isolation:

• Wearing a lab coat
• Using safety glasses
• Wearing gloves to prevent absorption through skin

Advanced isolation:

• Physical barriers or containers
• Automated systems that handle chemicals without human contact
• Sealed glove boxes or containment systems

Ventilation and fume extraction

Proper ventilation systems remove chemical vapours from the breathing zone, significantly reducing inhalation risks.

In the laboratory:

A fume cupboard is a ventilation system that uses fans to draw fumes upward and away from the user. All work with volatile organic compounds should be conducted in a fume cupboard.

In industry:

Giant extractor systems clear entire rooms and factories of vapours, reducing the chance of chemical inhalation for all workers in the area.

Disposal of organic compounds

Proper disposal of organic compounds is strictly governed by legislation in Australia to protect both human health and the environment.

Disposal procedures

In both laboratory and industrial contexts:

1. Waste is collected in designated containers
2. Waste is dealt with by specialised chemical waste disposal companies
3. Waste is often treated first to:
   • Remove acids or bases (by neutralisation)
   • Filter out metal solids or other solid materials

Separating different types of waste

Different types of organic waste are kept separate because they:

• Pose different hazards and risks
• Require different treatment methods
• May react dangerously if mixed together

The "sink rule"

Waste reduction in the laboratory

In your classroom, there should always be a designated waste container for organic chemicals. Always empty all organic waste into this container, never down the sink.

Practical investigations involving organic substances use very small amounts because:

• Reduction of waste volume is important
• Smaller amounts are safer to handle
• Less waste needs to be disposed of

Remember!