Organic Chemistry

Definition 

Organic Chemistry is that branch of chemistry that deals with the compounds that have carbon in them. Matters that have Carbon then are called organic compounds. Organic chemistry studies the features characteristics, structure and reactions of these organic compounds.

By definition, we call those compounds organic that have carbon in them. However, there are certain Carbon compounds that are not organic. Why? Because in these compounds the carbon atom is not bonded with a hydrogen atom. Take the example of CO2. Here, we see that carbon dioxide has carbon but no hydrogen. Hence, the true definition of organic would be like this - Compounds that have carbon and hydrogen ( and other elements) are called organic compounds. But then again Carbon tetrachloride is considered as organic despite having no hydrogen. The organic vs inorganic debate will thus see no end.

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The Theory of Vitalism 

In the early days - as early as the 17th century - organic compounds were thought to be created only in the bodies of living beings. This is how early chemists used to differentiate between organic and inorganic compounds.

However, in 1828 Frederick Woehler accidentally obtained urea from ammonium cyanate - an inorganic compound. Now if you look at the chemical symbol of urea - CH4N2O - is a classic example of an organic compound. It has Hydrogen and Carbon. It is produced in our intestines. At the same time, it can be produced artificially as proven by Woehler. So the theory of vitalism is basically an incorrect theory.

Importance of Organic Chemistry 

In order to understand the importance of organic chemistry, you need to understand how we are engulfed by carbon-based materials all around. Literally - you are engulfed by your skin and this skin is made up of carbon. We live in a carbon word - as you have heard this many times.

Carbon has Three Properties:

  • Carbon is tetravalent. It has 4 electrons in its valence shell. So it is always on the lookout filling up this shell and making the total number of electrons reach 8.

  • Since the carbon electrons are too much attracted by the neutron, it cannot lose electrons easily. Neither can it take electrons from others because of its small size. What it does is, it shares its electrons with other atoms. The two (or more) atoms use each other’s electrons.

  • Since carbon’s neutron(s) has a strong attraction force, it also attracts the electron of the atom whose electrons it is sharing. This strong attraction force keeps the bond between the carbon atom and the other atom strong and stable. As a result, the carbon atom is able to go on making long chains of compounds.

These three features of carbon - particularly its long chain-forming nature - is what enables it to form so many compounds.

The clothes you wear are made of carbon. The food you eat is made of carbon. That pet dog that you are caressing is also made of carbon. Your school bus needs carbon to run - petrol is made of carbon. The medicines that people need to get healthy are made of carbon. And things that are made of carbon are all organic materials. So the uses and application of organic materials are vast. Without organic compounds, humanity and human society would not have been there. To deal with these materials, improve them and figure how we can use these materials for our benefit, we need organic chemistry to examine them closely.

Classification of Organic Compounds  

Organic compounds are mainly classified into two groups: 

  • Aliphatic/Acyclic Compounds

  • Cyclic Compounds

Aliphatic compounds are those compounds in which atoms are bonded together to form chain-like structure. Since the atoms in these compounds do not form a closed loop, the compounds are sometimes called open-chain compounds. Cyclic compounds are those compounds in which the atoms are bonded together in a cyclical form.

Aliphatic Compounds are Further Divided Into -

  • Straight chain compounds

  • Branched-chain compounds

Straight chain compounds are those that have no atoms (or chemical group as you may call it) attached to the parent chain or the main chain. In other words, the chain of atoms is straight without having any extra branch of atoms replacing some of the hydrogen atoms.

Branched-chain compounds have side chains - extra atoms (or chemical groups) attached to the core body of the compound. The chemical group replaces some of the hydrogen atoms in the core chain and gets attached to it.

Cyclic Compounds are Further Divided into Two Groups - 

  • Heterocyclic Compounds - That have other atoms apart from the carbon atoms.

  • Homocyclic Compounds -  That are made up of only carbon atoms.

The above Two Compounds are Further Divided into Two Groups -

  • Alicyclic Compounds - That have no pi electrons and no aroma.

  • Aromatic Compounds - That have an aroma and (4n + 2) pi electrons.

Heterocyclic Aromatic Compounds can Further be Divided into -

  • Benzenoid  - Having at least one Benzene ring.

  • Non-Benzenoid - Having no Benzene ring but does have aligned P orbitals.

The Hybridisation of Organic Compounds 

We know that the carbon has two electrons in the S subshell and two electrons in the P subshell. (Remember when we are talking about the S subshell, we are actually mentioning the 2S subshell or the outer subshell. The inner S subshell should always have 2 electrons) In its original form, the carbon has two S has electrons and two P electrons. So if it were to be bound with another atom - there would be 2 bonds from the S orbital and 2 bonds pertaining to the P orbital.

The thing is, evidence shows that bonds pertaining to carbon do not happen that way. In the excited state, the 2S subshell donates 1 electron to the P subshell. This gives rise to the following scenario -

  • The S2P2 configuration is changed to S1P3 configuration and we have a combination of 1S electron and 3P electrons. These electrons are similar or homogeneous in nature. This kind of scenario results in pure sigma bonds.

  • Although the S subshell donates one electron to the P subshell, there is one P electron that is unavailable. So in case of the bonding of two of these kinds of atoms, the two P electrons and one S electrons of each of these atoms will act usually, but the unavailable P electrons in the two will overlap each other’s orbits forming a pi bond.

  • If two of the P electrons are unavailable, the single P electron from each of the atom and the single S electron from each of the atom will act usually and there will be sigma bond between the combined S and P shells but there will be the pi bond between the each of the unavailable P electrons of each of the atoms.

These scenarios are called the hybridization of the carbon.

You have seen the movie, Antman. We know you were excited about the ability of the Antman to go subatomic. If you read this chapter well, you can actually understand how atomic particles in reality work. Just think about the intricate things that are going on at the atomic level - it is just astounding.

FAQ (Frequently Asked Questions)

1. Tell me Something about the Representation of Organic Compounds.

Ans. Organic compounds are represented in 4 ways:

  • Complete Structural Formula- In this representation, we mention the whole atomic structure of the compound.

  • Condensed Structural Formula- In this representation, we do not write the whole atomic structure. We do not write the symbol of the element as many times as it is present in the compound. We just mention how many of each of the elements is present in the compound by writing the number beside the chemical symbol of the element.

  • Bond Line Formula- Here bonds are represented with a line connecting two atoms.

  • 3 Dimensional Formula- Here the structure shows exactly where the elements or electrons are. The angle between the two-electron, the height of the atoms - all can be identified with the help of 3-dimensional formula

2. What is the Rule Pertaining to the Nomenclature of Organic Compounds?

Ans. The International Union of Pure and Applied Chemistry is the one behind the formulation of the rules of nomenclature. This nomenclature system is quite robust and logical. The functional group is denoted by the suffix. The number of carbon atoms is denoted by the prefix of the compound’s name. There are rules for the branched groups, there are rules for the alkyl halides - mo aspect has been left out.

3. What are the Functional Groups?

Ans. Functional groups are those groups of atoms that are attached to the core molecular framework of a compound. This functional group gives the molecule its unique characteristics.

4. What are Homologous Series?

Ans. A group of organic compounds that contain the same kind of functional group is called the homologous series. Example - Methane, Ethane, Propane, Butane.

5. What is Isomerism?

Ans. The case of having two or more organic compounds that possess the same molecular formula but different properties is known as isomerism. This difference of properties is because of the different arrangements of the atoms.