Topic 1.7Introductory organic chemistry

Crowe2008

About organic chemistry: hazard and risk in organic chemistry

Objectives - To be able to:

•appreciate the difference between hazard and risk

•understand the hazards associated with organic compounds and why it is necessary to carry out risk assessments when dealing with potentially hazardous materials

•suggest ways that risk can be reduced and reactions can be carried out safely

Starter - Sketch the labels for the following hazards:

Corrosive, harmful, toxic, flammable,

dangerous to the environment

What colour are these labels?

What captions appear on these labels?

What is chemistry?

Chemistry is the science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions.

Areas of chemical study

Inorganic chemistry, the study of inorganic matter

Organic chemistry, the study of organic matter

Biochemistry,

the study of substances found in biological organisms

Physical chemistry, the energy related studies of chemical systems

Analytical chemistry, the analysis of material samples to gain an understanding of their chemical composition and structure.

Plus many other sub-divisions

The core principles of chemistry

Chemical Ideas:

•Understanding and explaining the ways in which different chemicals react with one another.

How Chemists Work:

•Seeing how chemical theory and knowledge has been developed and extended over time.

•Building your own practical skills.

Chemistry in Action:

•Use and abuse of chemicals.

•Recycling & sustainability.

•Ethics & Economics

Organic Chemistry

This is the study of the compounds of carbon, except for carbon monoxide, carbon dioxide and the carbonates.

Why are there so many carbon compounds?

What is unusual about the way that carbon can form bonds?

•Carbon is in Group 4 and so can form four covalent bonds

•It can also form double and triple bonds

•It forms chains and rings of carbon atoms joined together

•Such chains and rings of carbon atoms are the basis for whole families of organic molecules, such as;

hydrocarbons, carbohydrates, proteins, amino acids etc.

Hazard & Risk in organic chemistry

Hazard – the potential to do harm

Suggest some hazards in the laboratory

2. Hazards arising from the activities performed in the laboratory: heating, pouring, spilling, etc.

1. Hazards presented by the substances themselves

Hazard & Risk in organic chemistry

Risk – the chance that a particular hazard

will actually cause harm.

Risk is affected by a number of things, in particular the nature of the hazard and the level of exposure involved..

•Expertise of person

•Quantities being used

•Conditions in which it is used

•Protective clothing & equipment used

Affected by

A hazardous substance can be safe to use if the risks are minimised

How science works – managing hazard, calculating risk

See active book p97

• Write the five steps needed to make a risk assessment

Ways of reducing risk

1. Working on a smaller scale

What is the advantage here if

(a)The substance produces harmful fumes?

(b)The reaction is exothermic?

(c)The substance needs to be poured from one container into another?

Ways of reducing risk

2. Taking specific precautions or using alternative techniques depending on the properties of the hazardous substances used.

e.g. concentrated acids and alkalis are corrosive, whereas their diluted solutions are irritants.

Many reactions can be performed using diluted reagents, however there are certain reactions where the concentrated chemical must be used, what precautions could you take to minimise the risk?

Ways of reducing risk

3. Careful use of fume cupboards and personal protection, considerably reduce the risk of carrying out reactions using hazardous chemicals

(a) What are the benefits of carrying out a reaction in a fume cupboard?

(b) Make a list of personal protection items that you could use while performing an experiment.

Ways of reducing risk

4. Changing the conditions under which a reaction takes place

How would lowering the temperature of a reacting mixture reduce risk?

Less chance of overheating

Less chance of harmful fumes being released

Ways of reducing risk

5. Using alternative methods with less harmful substances

Sometimes it is possible to substitute a hazardous chemical with one that is less hazardous. However, In many cases the replacement chemicals are less effective (e.g. slower reaction, lower yield of product). Suggest why these methods are still used?

The risk is lower and so the disadvantages are worthwhile.

See active book pp98/99 HSW pesticides and comparative risks

Summary Questions

1. What is the difference between hazard and risk?

2. Why are chemical and explosives laboratories relatively safe places to work?

3. What ethical issues would you need to consider when deciding whether to use natural or synthetic pesticides on a large scale?