Chemistry:

Chemistry is the science of molecules and their transformations. It is the science not so much of the one hundred elements but of the infinite variety of molecules that may be built from them.Chemistry deals with the composition, structure and properties of matter. These aspects can be best described and understood in terms of basic constituents of matter: atoms and molecules. That is why chemistry is called the science of atoms and molecules. Can we see, weigh and perceive these entities? Is it possible to count the number of atoms and molecules in a given mass of matter and have a quantitative relationship between the mass and number of these particles (atoms and molecules)? We will like to answer some of these questions in this Unit. We would further describe how physical properties of matter can be quantitatively described using numerical values with suitable units.

Importance Of Chemistry:

Science can be viewed as a continuing human effort to systematize knowledge for describing and understanding nature. For the sake of convenience science is sub-divided into various disciplines: chemistry, physics, biology, geology etc. Chemistry is the branch of science that studies the composition, properties and interaction of matter. Chemists are interested in knowing how chemical transformations occur. Chemistry plays a central role in science and is often intertwined with other branches of science like physics, biology, geology etc. Chemistry also plays an important role in daily life. Chemical principles are important in diverse areas, such as: weather patterns, functioning of brain and operation of a computer.

Chemical industries manufacturing fertilizers, alkalis, acids, salts, dyes, polymers, drugs, soaps, detergents, metals, alloys and other inorganic and organic chemicals, including new materials, contribute in a big way to the national economy. Chemistry plays an important role in meeting human needs for food, health care products and other materials aimed at improving the quality of life. This is exemplified by the large scale production of a variety of fertilizers, improved varieties of pesticides and insecticides. Similarly many life saving drugs such as cisplatin and taxol, are effective in cancer therapy and AZT (Azidothymidine) used for helping AIDS victims, have been isolated from plant and animal sources or prepared by synthetic methods. With a better understanding of chemical principles it has now become possible to design and synthesize new materials having specific magnetic, electric and optical properties. This has lead to the production of superconducting ceramics, conducting polymers, optical fibres and large scale miniaturization of solid state devices.

In recent years chemistry has tackled with a fair degree of success some of the pressing aspects of environmental degradation. Safer alternatives to environmentally hazardous refrigerants like CFCs (chlorofluorocarbons), responsible for ozone depletion in the stratosphere, have been successfully synthesised. However, many big environmental problems continue to be matters of grave concern to the chemists. One such problem is the management of the Green House gases like methane, carbon dioxide etc. Understanding of bio-chemical processes, use of enzymes for large-scale production of chemicals and synthesis of new exotic materials are some of the intellectual challenges for the future generation of chemists.

Organic Chemistry:

Organic compounds are vital for sustaining life on earth and include complex molecules like genetic information bearing deoxyribonucleic acid (DNA) and proteins that constitute essential compounds of our blood, muscles and skin. Organic chemicals appear in materials like clothing, fuels, polymers, dyes and medicines. These are some of the important areas of application of these compounds. Science of organic chemistry is about two hundred years old. Around the year 1780, chemists began to distinguish between organic compounds obtained from plants and animals and inorganic compounds prepared from mineral sources. Berzilius, a Swedish chemist proposed that a ‘vital force’ was responsible for the formation of organic compounds.rganic sources in a laboratory.

Organic chemistry describes the structures, properties, preparation, and reactions of a vast array of molecules that we call organic compounds. There are many different types of organic compounds, but all have carbon as their principal constituent atom. These carbon atoms form a carbon skeleton or carbon backbone that has other bonded atoms such as H, N, O, S, and the halogens (F, Cl, Br, and I).

Organic Molecules:

All organic molecules contain carbon (C), virtually all of them contain hydrogen (H), and most contain oxygen (O) and/or nitrogen (N) atoms. Many organic molecules also have halogen atoms such as fluorine (F), chlorine (Cl), bromine (Br), or iodine (I). Other atoms in organic compounds include sulfur (S), phosphorous (P), and even boron (B), aluminum (Al), and magnesium (Mg). The number of different types of atoms in organic compounds suggests they are structurally complex. Fortunately, we find these atoms in a relatively few specific arrangements because of their preferred bonding characteristics.

For example, C atoms primarily bond to each other to form the molecular skeleton or backbone of organic molecules, while H atoms bond to the various C atoms, or to other atoms such as N and O, almost like a "skin" surrounding the molecule. You can see some of these features in the organic molecule lauric acid that is one of a group of molecules called fatty acids. [graphic 1.1] Since atoms such as N, O, and the halogens (generally referred to as X) connect to the carbon skeleton in characteristic ways that determine the properties of a molecule, we call these groups of atoms functional groups. Functional groups define the class to which the organic molecule belongs.

Stereochemistry:

Stereochemistry is the study of the relative arrangement of atoms or groups in a molecule in three dimensional space.Stereochemistry, a subdiscipline of chemistry, involves the study of the relative spatial arrangement of atoms that form the structure of molecules and their manipulation.The study of stereochemistry focuses on stereoisomers, which by definition have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in space. For this reason, it is also known as 3D chemistry—the prefix "stereo-" means "three-dimensionality".An important branch of stereochemistry is the study of chiral molecules.

Stereochemistry spans the entire spectrum of organic, inorganic, biological, physical and especially supramolecule chemistry. Stereochemistry includes methods for determining and describing these relationships; the effect on the physical or biological  properties these relationships impart upon the molecules in question, and the manner in which these relationships influence the reactivity of the molecules in question.Stereochemistry is an important issue in any synthesis.

This artical illustrates two key points. First, disconnection should be done at a CC bond where one of the carbon atoms is a stereogenic center. Disconnection of a bond away from the stereogenic center usually leads to a less efficient and less desirable retrosynthesis, and often more difficult. The second issue deals with search engines. Searching exact structures with all sterochemistry intact  may return no hits, whereas the same search for the racemic structure may return many hits or at least related structures that can help with the planning. The main lesson is that one should not limit the search to the structure with all “wedges” and “dashes” incorporated, but also search using the racemic structure.Indeed, it maybe more useful to begin the search with the racemic compound and use that information to guide any search with the enantiopure compound.

The central atom is a stereogenic carbon because it has four distinct groups: Br, Me, Et, and H. A chiral object is one with a non-superimposable mirror image. The two versions of 2-bromobutane on either side of the mirror here are enantiomers. Note that there is no such thing as a “chiral carbon”; rather, we say that stereogeniccarbons cause the whole molecule to be chiral. (Note, however, that it is possible for a molecule to have stereogenic carbons and yet be achiral). The two molecules above have the same properties in almost every possible way.

Importance of Stereochemistry:

Stereochemistry aims to explain the natural phenomena of spatial arrangements of these organic molecules. Stereocenter: Any atom in a molecule that is attached to 4 different atoms. Also known as chiral center.For example, a molecule with 3 stereocenters would give rise to a molecule with 8 stereoisomers.Using stereochemistry, chemists can work out the relationships between different molecules that are made up from the same atoms. They can also study the effect on the physical or biological properties these relationships give molecules. ... An important part of stereochemistry is the study of chiral molecules.

Importance of Organic chemistry:

Organic chemistry is important because it is the study of life and all of the chemical reactions related to life. Several careers apply an understanding of organic chemistry, such as doctors, veterinarians, dentists, pharmacologists, chemical engineers, and chemists.Organic chemistry plays an important part in our daily life because food, clothes, paper, ink, rubber, soap, perfumes, medicines etc. are indispensable to us for properliving. Organic compounds are important constituents of many products e.g., paint, food, plastic, explosive, medicine, petrochemical, pesticide etc.Organic chemistry is a highly creative science in which chemists create new molecules and explore the properties of existingcompounds. It is the most popular field of study for ACS chemists and Ph.D.chemists. Organic compounds are all around us.