Organic Chemistry class 1

Introduction to Organic Chemistry

Organic chemistry is the study of carbon containing compounds and their properties. This includes the great majority of chemical compounds on the planet, but some substances such as carbonates and oxides of carbon are considered to be inorganic substances even though they contain carbon.Organic chemicals are continually released into the environment in large quantities. For example, global production of mineral oil exceeds 3 billion tonnes a year and the amount of new organic chemicals made each year in research laboratories and industry is increasing exponentially. There is a need to understand how these organic molecules will interact with the environment in order to minimise their impact. To achieve this the type of reactions that organic molecules undergo needs to be understood.

 How do you tell the difference between an Organic and an Inorganic Compound?

 Probably the best way is to compare the chemical and physical properties of substances to the table below. If they concur with those properties on the left column of the table then the substance is probably organic, whilst if they compare to the properties listed in the right column then the substance is most likely inorganic. 

Organic Compounds

1. Use mostly covalent bonding
2. Are gases, liquids or solids with low melting points Mostly insoluble in water 
3. Many are soluble in organic solvents such as petroleum, benzene and hexane
4. Solution in water generally do not conduct electricity Almost all burn
5. Slow to react with other chemicals 

Inorganic Compounds

1. Mostly ionic bonding 
2. Are generally solids with high melting points Many are water soluble
3. Most are not soluble in organic solvents
4. When dissolved in water conducts electrical current Most not combustible 
5. Often undergo fast chemical reactions

Table 1: Comparison of the properties of organic and inorganic compounds

The vast majority of organic compounds are typically chains or rings of carbon atoms that contain other elements such as O, N, P, S, Cl, Br and I. There are over five million of these compounds known today and an almost infinite number of new compounds could possibly be synthesized. This can be compared to the total number of inorganic compounds, which is approximately half a million.

Why does carbon form so many compounds?

Carbon has the ability to bond with itself to form long chains and ring structures; hence it can form molecules that contain from one to an infinite number of C atoms.

Additionally C atoms may:

• be bonded by multiple bonds (i.e. double and triple) as well as single

• contain branches of other carbon chains

• need additional atoms attached to them to make them stable. The most common of these is H, but, N, O, X, P and S also commonly occurs attached to C and may even be attached in several different ways.

 Note X is the symbol for any of the halides – F, Cl, Br or I

The Rules for Drawing Organic Molecules

1. C always has four bonds. This may consist of:

• 4 single

• 1 double and 2 single

• 1 triple and 1 single
• 2 double

2. H always has one bond.

3. O always has two bonds. This may consist of:

• 2 single
• 1 double

4. X always has one bond. X =  F, Cl, Br or I

5. N always has three bonds. This may consist of:

• 3 single

• 1 single and 1 double
• 1 triple

6. S may have 2, 4 or 6 bonds, but for this course it has 2 bonds.