[Chemistry Class Notes] on Carbon Compounds Pdf for Exam

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Carbon is the fourth element of the Periodic Table which is abundant in nature as well as the universe. It exists not only in atomic and crystalline forms but also as several compounds. Each carbon compound has distinctive properties and applications of its own.

An Overview

Carbon is such a versatile element that it is present in almost everything around us. From foods to clothes, medicines to books- carbon is the base of almost all structures including the living ones. Carbon is present in minerals in 0.02% amount and in the atmosphere, it is present as carbon dioxide in 0.03% amount. All products of coal and petroleum contain carbon in them. In fact, carbon continues to stay even in the organisms after death. Carbon is a non-metal element. 

Basic Information about Carbon

Symbol

C

Atomic number

6

Atomic structure

2, 4

Valence electrons

4, tetravalent

Nature

Non-metal

As carbon has a valency of four it refers to the fact that it can react with four atoms of elements (same or different) while forming a compound. 

How does Carbon Bond with Other Elements?

Carbon uses covalent bonds for achieving stability. By the use of this, carbon shares the valence electrons with other carbon atoms or different element atoms. If carbon did not use a covalent bond, it had two ways to attain stability one of them is gaining four electrons and the other being losing four electrons. But in the former way, it will be difficult for the six protons to carry on with ten electrons and in the latter way, a large amount of energy will be needed for removing four electrons. By forming a covalent bond, carbon uses shared electrons on the outermost shell and achieves the configuration of a noble gas. 

In covalent bonds, the intermolecular forces are less while the bonded molecules have strong bonds within the molecule. Also, no formation of charged particles is observed here. This contributes to the nature of being a poor electricity conductor. 

What are the Versatile Features of Carbon?

Carbon has two basic natures which make it the most extensively present element in organic compounds. These are catenation and tetravalent nature. 

  1.  Catenation 

Each and everything is surrounded by carbon compounds in the field of Organic Chemistry. Carbon compounds are one of the quintessential components of living organisms. Carbon consists of two stable isotopes namely 12C and 13C. Apart from these two isotopes there is another isotope of carbon existing in nature. It is 14C. Radiocarbon dating is done by the carbon and it is also a radioisotope with a half-life of 5770 years. 

  • One of the most unique properties of carbon is that it is able to make long carbon chains and rings. This unique feature of carbon is termed as catenation. 

  • Another amazing property of carbon is that carbon forms p-pπ bonds which are double and triple bonds with itself and with other electronegative atoms such as oxygen and nitrogen.

  • Carbon has a number of allotropic structures just because of these two properties of carbon i.e. catenation and multiple bond formation. 

The small size of the carbon atom and the carbon-carbon bond strength enables it to form stable multiple bonds too with itself and other element atoms. Propane and butane are two such straight-chain elements while 2-methylpropane and 2,2-dimethylpropane are two branched-chain elements. Cyclohexane and cyclobutane are two ring-structured elements.

  1.  Tetravalent Nature

This enables carbon bonds with four atoms of carbon itself or atoms of other elements with the help of a single, double or triple bond. 

What does the Allotrope of Carbon Actually Mean?

If an element is present in nature in various forms with various physical properties and similar chemical properties then its forms are termed as allotropes of allotropic forms. Two or more physical forms of one element actually define allotropes. Allotropes are formed on the basis of carbon atoms but exercise different physical properties, mainly with regard to hardness.

Diamond and graphite are the two most common crystalline allotropes of carbon. Recent researches reveal that all the amorphous carbons consist of microcrystal of graphite. In spite of the difference in the crystal structure and physical properties of these allotropes, their chemical properties are the same. Diamond and graphite bear the symbol C and both release carbon dioxide when strongly heated in the presence of oxygen.

What are Some Important Carbon Compounds?

Ethyl alcohol or ethanol and ethanoic acid are two of the most important carbon compounds. 

  1.  Ethanol

Its chemical formula is CH3CH2-OH or C2H5OH. It is a colorless inflammable liquid that, when added to water, forms a homogeneous mixture in all proportions. Litmus paper does not change color when brought in contact with ethanol. 

Some of its chemical properties are as follows:

  1.  It reacts with sodium to form sodium ethoxide

  2.  Ethanol reacts with concentrated H2SO4 which removes water from ethanol.

2.   Ethanoic Acid

This is commonly known as acetic acid with the chemical formula CH3COOH. When 5-8% of ethanoic acid is mixed with water, it is known as vinegar. Ethanoic acid freezes in an extremely cold climate and its melting point is 290K. Thus, it is also called glacial acetic acid. It is a pungent-smelling liquid devoid of any color. It is miscible with water and turns blue litmus red. 

Some of its Chemical Reactions are as Follow:

  • In the presence of concentrated H2SO4, ethanoic acid reacts with alcohol to give off a sweet-smelling ester. This is known as the esterification reaction. 

  • Ethanoic acid reacting with sodium carbonate or sodium bicarbonate produces carbon dioxide, water and sodium ethanoate salt. 

3.   Other Carbon Compounds

There are numerous carbon compounds. Among them, methane and carbon dioxide are of exceptional importance. 

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Name 

Methane 

Carbon dioxide

Chemical formula 

CH4

CO2

The atomic number of carbon 

6 (2, 4)

6 (2,4)

Number of valence electrons (of carbon)

4

4

The atomic number of hydrogen

1

Not applicable

Number of valence electrons (of hydrogen)

1

Not applicable

The atomic number of oxygen 

Not applicable

8 (2, 6)

Number of valence electrons (of oxygen)

Not applicable

6

What are the Chemical Properties of Carbon Compounds?

  1. Combustion 

When carbon compounds undergo complete combustion, carbon dioxide, water, heat and energy are produced. 

CH3CH2OH (I) + O2(g) → CO2(g) + H2O(I) + heat and light

Carbon itself burns in the presence of air to produce heat, light and carbon dioxide.

C (s) + O2 (g) → CO2(g) + heat and light

In the presence of air and oxygen, saturated hydrocarbons burn with a blue flame.

CH4(g) + O2(g) → CO2(g) + H2O(l) + heat and light

  1. Oxidation 

Ethanol is oxidized to ethanoic acid by oxidizing agents. When subjected to combustion, Carbon and its compounds get very easily oxidized.  For example, carboxylic acid is formed when alcohol gets oxidized. Oxidizing agents are those substances which can add oxygen to other compounds. Potassium dichromate and alkaline potassium permanganate are a few examples of oxidizing agents. In the presence of oxygen, carbon burns. After burning, Carbon gets oxidized to carbon monoxide or carbon dioxide. The end product depends on the availability of oxygen and the extent of the reaction. When it reacts with strong oxidizing agents, most compounds of carbon get oxidized. 

  1. Addition 

Unsaturated hydrocarbons and hydrogen undergo an additional reaction by the catalyst activity of nickel or platinum. This is a hydrogenation reaction. Saturated hydrocarbons are formed when, in the presence of catalysts, unsaturated hydrocarbons react with hydrogen. A substance that enhances the rate of a reaction without taking part in the reaction is known as a catalyst. An Additional reaction can only occur in those compounds that have multiple bonds (double bonds, triple bonds), that is, the compounds that are unsaturated. In the industry, an example of an additional reaction is the hydrogenation of vegetable oils. In this reaction, the addition of hydrogen in unsaturated vegetable oils occurs. This is done in presence of a catalyst to convert it into a saturated compound. 

  1. Substitution 

One or more hydrogen atoms of carbon compounds are replaced by another atom or group of atoms. 

Substitution reactions are those reactions where a less reactive molecule or element gets replaced by a more reactive molecule or element. In the case of saturated hydrocarbons, substitution reactions are mostly observed. Next, we are coming to an example of a substitution reaction in carbon and its compounds. When saturated hydrocarbons react with chlorine in the presence of sunlight, it is a substitution reaction. Chlorine is more reactive and hence has the ability to displace the hydrogen atom from saturated hydrocarbons. Higher homologs of the same hydrocarbons are generally the end products of this reaction.