Organic and Inorganic Compounds

The modern definition of organic compounds is generally based upon the idea that they contain the element carbon.  However, defining organic compounds also includes those inorganic compounds which contain carbon (exceptions). Some of the carbon-containing inorganic compounds are carbonates, cyanides, cyanates, carbides, thiocyanates, carbon monoxide and carbon dioxide. A broader definition takes into account that organic compounds don’t just contain carbon. They contain carbon atoms covalently bonded to hydrogen.

History

For many centuries, scientists had believed in the idea of vitalism. According to this idea, all living organisms contained a life force, which differentiated them from non-living organisms. This force enabled the living organisms to produce certain chemical compounds. Scientists called these organic compounds. The belief in vitalism propagated the idea that organic compounds are unique to living organisms and only they are able to produce them. However, this belief was eventually refuted by modern experiments conducted on organic compounds. One of the modern scientists Friedrich Wohler managed to successfully prepare urea, which was considered an inorganic compound, from inorganic salts such as potassium cyanate and ammonium sulphate.

Classification of Organic Compounds

Organic compounds have been known to exist for thousands of years. At present, there might be more than 3 million organic compounds in existence.  For the sake of convenience, organic compounds have been classified into two main groups. The first group consists of compounds that contain only carbon and hydrogen atoms and are called hydrocarbons. They can be grouped into alkanes(single carbon bond), alkenes(double carbon bond), alkynes(triple carbon bond) and arenes(carbons formed into a cyclic ring called benzene). The second group consists of organic compounds which have replaced one of the hydrogen atoms with a functional group such as single atoms of F, Cl, Br or a combination of atoms like NH₂ and OH. These functional groups influence the chemical reactivity of the organic molecules and are an essential part of organic synthesis. Some examples are oxygen-containing groups (alcohols, ethers, aldehydes etc.), nitrogen-containing groups (amines and amides) and sulphur-containing groups (thiols, thioethers and thioesters).

Another method of classification of organic compounds is based on their structure. They are classified into three main groups based on the nature of their carbon chains. These groups are as follows:

1. Acyclic/Aliphatic Compounds- Organic compounds with open chin processing are called aliphatic compounds.
2. Carbocyclic Compounds-Organic compounds with rings consisting of sole carbon atoms are called carbocyclic compounds. These are further classified into:
3. Alicyclic Compounds- The organic compounds belonging to the class of carbocyclic compounds which behave like aliphatic compounds. Examples are cycloalkanes, cycloalkynes etc.
4. Aromatic Compounds-These organic compounds have benzene rings with a characteristic defining smell. Examples are benzene, toluene etc.
5. Non-Benzenoid Aromatic Compounds- These organic compounds do not possess benzenoid rings but still have a characteristic, defining smell. Examples are tetraphenyl chlorobutanol fluoroborate, potassium cyclopentadienide etc.
6. Heterocyclic Compounds- These are organic compounds that possess rings with carbon and other elements, usually oxygen, nitrogen or sulphur. These rings do have a characteristic aroma. These have five or six-membered stable heterocyclic rings which contain conjugated double bonds. Examples are furan, thiophene etc.

Classification of Inorganic Compounds

The classification of inorganic compounds is simpler. They are divided into acids, bases, salts and water.

1. Bases are compounds with a pH level above 7. Bases dissolved in water are referred to as alkaline. Also, bases can be used to neutralise acids. When bases react with acids, they produce byproducts of salt and water. Examples are sodium hydroxide and copper oxide.
2. Acids contain a hydrogen atom and an acid radical. They have their pH level below 7. They can also be formed using oxygen instead of hydrogen. Examples are hydrochloric acid and nitric acid.
3. Salts are formed from the residue of an acid and a metal. They are grouped into six different classes- medium, acid, basic, double, mixed and complex. Examples are sodium chloride and magnesium chloride.
4. Water, the most abundant compound on earth, is actually an inorganic compound. One strange fact about water is that it expands on freezing instead of contracting as seen in other cases.

Properties of Inorganic Compounds

The following are the properties of inorganic compounds:

• They have high melting and boiling points.
• They are soluble in water.
• They are good conductors of electricity.
• They are commonly not combustible.
• They are characterised by low volatility.

Properties of Organic Compound

The general characteristics of organic compounds are as follows:

• They can be isolated or prepared in laboratories.
• They encompass close to 90 per cent of all the known compounds.
• They are commonly made up of carbon, nitrogen and oxygen to a large extent. 

However, other elements also constitute a few organic compounds.

• They contain complex structures and have high molecular weight.
•  They are usually insoluble in water, but dissolve in organic solvents and are combustible.

Comparison and Differences

Constituent Element:

1. Organic Compounds- Carbon is a common constituent.
2. Inorganic Compounds- Carbon is usually absent.

Chemical Bonds:

1. Organic  Compounds- Covalent Bonds
2. Inorganic Compounds- Ionic, Covalent or Metallic Bonds.

Reactivity

1. Organic Compounds-Extremely reactive and combustible.
2. Inorganic Compounds- Non-reactive and inflammable.

Occurrence

1. Organic Compounds- Usually in living organisms.
2. Inorganic Compounds- This usually occur in non-living organisms.

Melting and Boiling Points

1. Organic Compounds-  Low
2. Inorganic Compounds- High

Conclusion

The chemical compounds can be distinguished on the basis of the presence of carbon. The two categories formed are named as organic and inorganic compounds. Organic compounds are the ones that have carbon atoms bonding covalently with hydrogen or other elements and are usually found in living organisms. Inorganic compounds usually have carbon absent in them and are commonly found in nonliving sources.