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# Organic Chemistry

The root word of organic chemistry, 'Organic' means that the compounds were synthesized from living organisms in the past.

Still now organic chemistry reactions involve the synthesis of organic compounds from living organism like starch, cellulose etc.

### Introduction to Organic Chemistry

1. Organic Chemistry is a sub division of Chemistry and it deals with the scientific study of structure, properties and the compositions of compounds. This is also considered as the chemistry of carbon containing compounds.
2. Every living organisms, irrespective of plants and animals are composed of organic compounds and anyone with an interest in life would definitely like to know more about the molecules involved in these life processes, which would require a basic understanding of organic chemistry.

## What is Organic Chemistry?

Organic chemistry is the branch of chemistry dealing with compounds containing carbon-carbon bonds. These carbon compounds are special in nature because most of them covalent in nature and they are highly volatile. As organic compounds have some distinguishing characters they are differentiated from rest of the chemistry and studies separately.
The next interesting thing is the number of organic compounds. As carbon can form a long chain due to its catenation ability (an ability to form long chains with itself and with other atoms) it can form many number of compounds. Hence we have to study the properties of organic compounds separately.

## Organic Chemistry Definition

Organic chemistry is the branch of chemistry dealing with organic compounds made up of covalent carbon chain. This branch is unique in studying the properties of organic compounds as all of them are covalent and they undergo different set of reactions from Inorganic compounds.

## Organic Chemistry Functional Groups

One of the special feature of organic chemistry which differentiates it from Inorganic chemistry is the compounds will form a pattern called homologous series. Every organic compound will have a specific part or group where the reactivity is more. This part is called as functional group in the organic compound.All the organic compounds with same functional group will fall under the same homologous series. They will have same chemical properties which make the study of organic chemistry much more easier.
For example in the following compounds the hydroxy (-OH) is the functional group and all the compounds are called as alcohols with same physical and chemical properties.

The special nature of functional group is all the compounds with same functional group will have same chemical properties. But the physical properties may differ with the number and nature of carbon chain.

For example both methanol and butanol will fall under alcohol series. Both will react with sodium to liberate hydrogen gas.

2CH3OH + 2Na $\rightarrow$ 2CH3ONa + H2
2CH3CH2CH2OH + 2Na
$\rightarrow$ 2CH3CH2CH2ONa + H2

## Organic Chemistry Reactions

Organic chemistry reactions are different from inorganic chemistry reactions. As most of the organic compounds are covalent in nature, the organic chemistry reactions involves the cleavage of the covalent bonds and forming of new bonds.

A covalent bond is made up of two electrons and cleavage of such bond may happen in such a way that both the electrons are taken away by one atom resulting in formation of ions.

On the other hand the bonding electrons may be equally divided between atom giving rise to free radicals. Hence organic chemistry reactions proceed by the formation of ions or free radicals.

### 1. Hence the organic chemistry reaction may be classified as

• Free radical reaction where radicals are formed and initiate the reaction, For example bromination of methane involves formation of bromine free radical to proceed the reaction. Hence the reaction is free radical reaction.
CH4 + Br. $\rightarrow$ CH3Br
• Nucleophilic reaction where negative ions are produced and attack on positive sides. For example the carbonyl carbon is partially positive charged and negative ions will attack on the carbon easily. Hence all the reactions in aldehyde and ketone are nucleophilic reactions involving negative ions.
• Electrophilic reaction where positive ions are produced and attack on negative sides. For example benzene ring is a rich source of Î electrons. Hence all the reactions will proceed with the attack of this electron by positively charged ions. Hence all the reactions in the benzene ring are electrophilic reactions.

### 2. The organic chemistry reactions may also further divided as

• Addition reaction: where an atom or group is added across an unsaturated bond. For example addition of bromine with ethylene gives di-bromo ethane.
CH2=CH2 + Br2 $\rightarrow$ CH2Br-CH2Br
• Elimination reaction: where a molecule is eliminated from an organic compound to give unsaturated compound. For example ethyl bromide on elimination in the presence of alcoholic KOH gives ethene.
CH3-CH2-Br $\rightarrow$ CH2=CH2 + HBr
• Oxidation reaction: It is the type of reaction where oxygen is added or hydrogen is removed from an organic compound. For example ethyl alcohol on strong oxidation in the presence of acidified potassium permanganate gives acetic acid.

• Reduction reaction: It is the type of reaction where oxygen is removed or hydrogen is added to an organic compound. For example acetone on reduction with lithium aluminum hydride gives 2-propanol.

• Condensation reaction: It is the type of reaction where two organic compounds combine together to give one compound by elimination of simple molecules like water, HCl etc. For example condensation of acid and alcohol gives ester.
CH3-CH2-OH + CH3COOH $\rightarrow$ CH3CH2OCOCH3 + H2O
• Polymerization reaction: It is the reaction in which small organic molecules called as monomers combined together to give a large chain of macro molecule called as polymer. Polymerization of vinyl chloride gives polyvinyl chloride, shortly called as PVC.

• Substitution reaction: It is the reaction in which an atom or group is replaced by another atom or group in an organic compound. For example, chloro methane reacts with potassium hydroxide to give methanol and potassium chloride.
CH3-Cl + KOH $\rightarrow$ CH3OH + KCl

Organic chemistry holds a central place in chemical studies because its fundamental principles and its applications touch virtually all other disciplines. Organic chemistry became a defined science in the nineteenth century, but organic compounds have been known and used for millennium.

Humans have used practical application of chemistry for thousands of years. The discovery of folk medicines, the development of metallurgical techniques and the use of natural dyes are simple organic chemistry examples.

## Organic Chemistry Nomenclature

Nomenclature the set of accepted conventions for organic chemistry naming compounds, is crucial to a discussion of organic chemistry. The rules of nomenclature presented only for general cases. The emphasis on nomenclature varies greatly from one course or examination to another.

There are two kinds of nomenclature in organic chemistry. One type involves being given the name of a compound and having to draw its structure. Alternatively one may be given a structural drawing and be expected to provide a correct name for the molecule.

## Physical Organic Chemistry

Physical organic chemistry is a relatively modern field with deep roots in chemistry. The subject is concerned with investigations of organic chemistry by quantitative and mathematical methods. Physical organic chemist are interested in understanding the underlying principles that determine why atoms behave as they do so.

## Organic Chemistry Problems

Some of the organic chemistry solved problems are given below.

### Solved Examples

Question 1: CH3CH2CHO $\xrightarrow[NaOH]{\Delta}$ product A. Find the product A
Solution:

During aldol condensation reaction the base abstracts the $\alpha$ - H atom of CH3CH2CHO molecule to produce nucleophile. So the product of the above reaction is CH3CH2CH=C(CH3)-CHO

Question 2: In the following reaction
CH3COCH3 $\overset{SeO_{2}}{\rightarrow}$ B.
Find the product B.
Solution:

SeO2 can oxidizes at the $\alpha$ - carbon.
So the correct answer is CHO-CO-CH3

 More topics in Organic Chemistry Alcohols Hydrocarbons Nitro Group Organic Chemistry Reactions Organic Chemistry Nomenclature Chemical Bonds VSEPR Model Hybrid Orbitals Models of Chemical Bonding Cycloalkane Alkenes Alkyne Amines Benzene Phenol Aryl Halide Carbohydrates Carboxylic Acid Aldehydes and Ketones Ester Carbon Compounds Organic Chemistry Practice Problems Acetal
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