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Modern Definition of Organic Chemistry for IIT JEE

Last updated date: 05th Dec 2023
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Different Types of Organic Compounds

The word “Organic” implies concerning life. Compounds that are organic by nature are composed of only animals, plants or an extracted form of animals and plants. They are not manufactured in the laboratory.

Initially organic chemistry was referred to as the study of those compounds that were formed by life on the planet. The definition included all those compounds that occurred naturally and not from mineral origin. 


One of the examples of an inorganic form of compound is “table salt”. Another very popular organic compound is urea. Also, this chemical compound is produced by several different organisms. Its chemical formula is CO(NH2)2. It is the first recognized organic form of compound that is made in the laboratory.


As per the discovery done by the famous scientist Friedrich Wöhler in the year 1828, it was found that urea can be easily prepared from inorganic materials. That was believed to be a significant conceptual milestone of the entire chemical industry.

It showed that the substance was earlier known only “as a byproduct” that can be artificially prepared in the laboratory without using any biological devices and materials. This finding was contradictory to the broadly held “doctrine of vitalism.”


Thus, the definition of organic chemistry became more refined and improved. The above conclusion was added into the original definition of“organic chemistry”. Now the modern definition of organic chemistry is stated as:

“Organic chemistry is considered to be a subdiscipline in chemistry that involves the scientific analysis of the properties, reactions and structure of all organic compounds as well as organic materials (present in varying forms containing C (carbon) atoms.”


The entire analysis of the structure of an organic compound includes several chemical and physical methods to provide the chemical constitution and the chemical composition of the different organic materials and compounds. 


Study of properties of organic compounds includes chemical properties as well as physical properties. It makes use of the same type of methods and the ones needed to evaluate chemical reactivity. The basic purpose of carrying out an analysis is to effectively understand the varying behaviour of organic matter in the purest form and in mixtures, solutions, and fabricated forms. 


Analysis of organic reactions includes leaning about their scope by the use of information of resultant compounds such as drugs, polymers, natural products, etc. This study is performed by using chemical synthesis procedure, and the attentive analysis of the reactions of organic molecules practically in laboratories and also through theoretical study.


Organic chemistry is a stream of science that involves understanding the structure, composition, properties, preparation and reactions of compounds that contain carbon in them. This list of compounds not just includes hydrocarbons but also a few compounds that include hydrogen, oxygen, nitrogen, phosphorus, halogens, sulfur and silicon. Most of the compounds that are considered for the study have at least 1C-H or carbon–hydrogen bond.


As per the basic definition of organic chemistry, organic stream of chemistry was limited to only those compounds that are generated by living organisms. This definition has been revised with the discoveries of various scientists with regards to organic compounds. 


The modified and revised definition of organic chemistry covers a broad horizon that includes man-made substances like plastics too. The field of usage of organic compounds is vast. It is not just limited to petrochemicals, pharmaceuticals, explosives, food, cosmetics and paints.


(NH4Cl)+ 2(KCNO) = 2(NH4CNO) + KCl


(Ammonium Chloride) + (Potassium Cyanate) = Ammoniamcynate


NH4CNO is Urea. It can be shown in the form of chemical structure 2(NH2----C-----NH2)


Name of the scientist who performed this study was Friedrich Wohler. This study of organic chemistry was carried out in the year 1828.


Modern definition of Organic chemistry includes analysis of chemical properties, structures and reactions of all Carbon Compounds. Based on the study performed by scientists, it was concluded that organic compounds are made up of covalent bonds. Some of the compounds that are characterized as organic include clothes, food, drugs, petroleum, plastics, dyes, leather, rubber, perfumes, pesticides, explosives, and polymers.


Natural sources of organic compounds are mentioned below:


Plants based sources: sugar, starch, drugs obtained from natural dyes and plants, and cellulose. 


Animals based sources: Proteins, fats and urea,


Coal based sources: Fuels, gas and aromatic compounds


Different kinds of organic compounds:


The classification of organic compounds is done as:


1. Non-cyclic or Acyclic compounds


2. Closed Chain or Cyclic Compounds


Non-cyclic or Acyclic compounds


These compounds are defined as:


• Carbon atoms that are joined in a straight chain


• A branched chain and a long chain compound


• They are also known as Aliphatic Compounds


Closed chain or cyclic compounds;


These compounds are classified as:


1. Carbocyclic compounds


a. Alicyclic Compounds


b. Aromatic Compounds.


2. Heterocyclic Compounds.


Carbocyclic compounds


These are the compounds that are composed of carbon atoms in a ring-like structure. They are bifurcated into two categories:

One is Alicyclic Compounds or non-benzenoid compounds and another is Aromatic compounds or Benzenoid compounds.

Alicyclic Compounds or non-benzenoid


• Closed ring or ring-like structure


• Just carbon atoms.


• Carbon atom that are joined via a single bond


• Shows characteristic similar to an aliphatic compound for example cyclohexane, cyclobutane, cyclopantane etc.


Aromatic compounds or Benzenoid compounds


These types of compounds are characterized as:


• Closed Chain Compounds


• Resonance structure


• Alternative single as well as double bond


• Aromatic compounds for example Phenol, Benzene, naphthalene, toluene, etc.


Hetrocyclic compounds;


These compounds are closed ring or Cyclic Compounds. They are characterized as 


• Containing 1 or 2 atoms besides carbon for example O, S and N


• Furan (5 membered),


• Pyridine (6 membered)


• Thiophene (4 membered)


Modern classification in organic chemistry and associated ambiguities


The L-isoleucine molecule having a chemical formula “C6H13NO2” shows features that are typically found in any organic compound. Carbon atoms are generally black in colour, hydrogen is grey in colour, oxygen is red in colour, and nitrogen is blue in color. Though vitalism theory has been condemned, scientific nomenclature still retains the difference between inorganic and organic compounds. 


The modern definition of organic compound implies to any compound that consists of a major portion of carbon in it. Most of the organic compounds that are known today do not have any connection with any substance that is present in the living organisms. The term “carbogenic” was proposed by scientist E. J. Corey, as an innovative alternative to the original organic definition, but the neologism still remains unclear.


The organic compound “L-isoleucine” presents a few characteristics of organic compounds such as carbon–hydrogen bonds, carbon–carbon bonds, and covalent bonds from C (carbon to oxygen) and (carbon to nitrogen).


Any definition given to explain the nature of organic compounds makes use of simple and widely applicable criteria that ultimately comes out to be inacceptable, to a large extent. The contemporary and commonly accepted organic compound definition amounts to a carbon containing compound that excludes various classes of substances that are traditionally referred to as 'inorganic'. 


Looking at the list of carbon containing compounds, there are a few compounds that should not be put into the category of organic compounds. For example, almost all authorities need the elimination of alloys that have carbon in them. It can be in the form of steel (Fe3C), semi-metal carbides that includes "ionic" carbides, such as CaC2, Al4C3 and "covalent" carbides, such as SiC, B4C and a graphite intercalation compound KC8


Other materials and compounds that are referred to as 'inorganic' by several authorities include: simple oxides such as CO2

CO, and C3O2, the carbon allotropes, cyanide derivatives that do not contain an organic residue such as KCN, BrCN, (CN)2, CNO− etc., and heavy analogs such as CP− 'cyaphide anion', COS, CSe, carbon disulfide are mostly classified in the form of an organic solvent. 


Halides of C (carbon) without hydrogen such as CClF3 and CF4, carboranes, phosgene (COCl2), metal carbonyls like nickel carbonyl, exotic oxo-carbons and mellitic anhydride (C12O9) are considered as inorganic compounds by a few authorities.

Nickel carbonyl and various other metal carbonyls represent an interesting scenario. They are volatile liquids just like several other organic compounds, but still contain carbon bonding to oxygen and transition metal. They are mostly formed directly from carbon monoxide and metal. 


Nickel carbonyl is mostly regarded as an organometallic compound. Although several organometallic chemists still use a broader definition where any compound that contains a (carbon-metal) covalent bond is thought to be organometallic. This issue is debatable whether such organometallic compounds come under the category of an organic compound or not. 

Metal complexes with an organic ligand but without any carbon-metal bond are not considered to be organometallic in nature. They are classed as a metalorganic. In the same way, it is quite uncertain whether metalorganic compounds have to be automatically considered as an organic substance.


The narrow definition of an organic compound that contains C-H bonds excludes compounds that are considered as organic. So, this implies that neither oxalic acid not urea is an organic compound by this definition. There are a few compounds that do not have C-H bonds but are still traditionally referred to as organic compounds. These are mesoxalic acid, benzenehexol, mellitic acid and carbon tetrachloride which do not have C-H bonds but yet they are considered to be organic substances.