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Organic chemistry, Organic chemistry is the study of the structure, properties, composition, reactions, and, preparation of carbon-containing compounds. Most organic compounds contain carbon and, hydrogen, but they may also include any number of other elements (e.g., nitrogen, oxygen,, halogens, phosphorus, silicon, sulphur)., Or, Organic chemistry limited to the study of compounds produced by living organisms, organic, chemistry has been broadened to include human-made substances (e.g., plastics)., Organic compounds are all around us. Many modern materials are at least partially composed of organic, compounds. They’re central to economic growth, and are foundational to the fields of biochemistry,, biotechnology, and medicine. Examples of where you can find organic compounds include, agrichemicals, coatings, cosmetics, detergent, dyestuff, food, fuel, petrochemicals, pharmaceuticals,, plastics, and rubber., , Tetravalency of Carbon Shapes of Organic Compounds, 1. Catenation – Catenation can be defined as the selflinking of atoms of an element to form chains and rings., This definition can be extended to include the formation, of layers (two-dimensional catenation) and space lattices, (three-dimensional catenation)., 2. Tetravalency and small size – Carbon exhibits’, tetravalency. The tetravalency of carbon can be satisfied, by forming bonds with carbon, hydrogen or other atoms., The carbon atom has 4 electrons in its valence shell. In, order to account tetravalency it is believed during the, process of bond formation which is energy-releasing, process the two electrons in the 2s orbital get unpaired, and out of them, one is promoted to empty orbital., , Structural Representations of Organic Compounds, 1. Complete, Structural, Formula – Full structural, equations show all the, atoms in a molecule, the, types of bonds that bind, them, and how they are, interconnected., 2. Condensed, Structural, Formula – The Condensed, structural formula is used to, save space; structural, formulas are conveniently
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abbreviated as condensed structural formulas., , 3. Bond Line Structural Formula – A bond-line structure, is a less cluttered drawing than a condensed structural, formula. However, to understand the simplified bond-line, structure, the reader has to mentally add many more features, to comprehend the overall structure., , Classification of Organic Compounds, 1. Acyclic or Open Chain Compounds & Alicyclic or Closed Chain or Ring Compounds, – Organic compounds are classified as open-chain compounds and closed chain compounds in terms, of the carbon chain. Also termed as Organic Compounds Acyclic or Open Chain or Aliphatic, Compounds Cyclic or Closed Chain or Ring Compounds Alkanes Alkenes Alkynes, 2. Aromatic Compounds – Plants and micro-organisms have an exclusive route to benzene-ring, compounds. The great majority of aromatic compounds in nature, therefore, are produced by plants, and microorganisms, and animals are dependent upon plants for many aromatic compounds either, directly or indirectly., 3. Heterocyclic Aromatic Compounds – In the twentieth century it is witnessed that the first, inorganic heteroaromatic compound produced in the laboratory. Some of these heterocyclic, aromatic compounds are very important in biochemical processes, drugs, and agrochemicals., , IUPAC Nomenclature, IUPAC nomenclature of organic compounds refers to the systematic approach taken, for the nomenclature of organic compounds as per the recommendation of, the International Union of Pure and Applied Chemistry (often abbreviated to IUPAC).
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The necessity for such a systematic approach arose due to the sheer quantity of new discoveries of organic, compounds which made the trivial nomenclature of organic compounds highly inconvenient., However, the IUPAC nomenclature guidelines are not always followed by chemists since some compounds, have very long and extremely tedious names as per the IUPAC nomenclature guidelines. These compounds, are assigned more trivial names., Ideally any conceivable organic compound should have a name from which to construct an unmistakable, structural formula. Inorganic chemistry also has an IUPAC nomenclature., In order to avoid long and tedious names in normal communication, the official recommendations for naming, IUPAC are not always followed in practice, except when a compound has to be given an unambiguous and, absolute definition. Sometimes, IUPAC names may be simpler than older names, as with ethanol, rather than, ethyl alcohol., They can be more easily understood for relatively simple molecules than non-systematic names which have, to be learned or looked over. The common or trivial name, however, is often considerably shorter and clearer,, and so preferred. Such non-systematic names are often derived from an original compound source., Furthermore, very long names may be less obvious than structural formulas., According to the Guidelines set by IUPAC, the nomenclature of compounds must follow these steps:, 1. The Longest Chain Rule: The parent hydrocarbon must be identified and subsequently named., The parent chain belonging to the compound in question is generally the longest chain of carbon, atoms, be it in the form of a straight chain or a chain of any other shape., 2. The Lowest Set of Locants: The carbon atoms belonging to the parent hydrocarbon chain must be, numbered using natural numbers and beginning from the end in which the lowest number is assigned, to the carbon atom which carries the substituents., 3. Multiple instances of the same substituent: Prefixes which indicate the total number of the same, substituent in the given organic compounds are given, such as di, tri, etc., 4. Naming of different substituents: In the organic compounds containing multiple substituents, the, corresponding substituents are arranged in alphabetical order of names in the IUPAC nomenclature, of organic compounds in question., 5. The naming of different substituents presents at the same positions: In the scenario wherein two, differing substituent groups are present at the same position of the organic compound, the, substituents are named in ascending alphabetical order., 6. Naming Complex Substituents: Complex substituents of organic compounds having branched, structures must be named as substituted alkyl groups whereas the carbon which is attached to the, substituent group is numbered as one. These branched and complex substituents must be written in, brackets in the IUPAC nomenclature of the corresponding compounds., The format of the IUPAC Name of the Compound can be written as: Locant + Prefix + Root + Locant +, Suffix, , 1. Root, The Word root indicates the total number of carbon atoms present in the longest carbon chain belonging to, the compound. For example, ‘Meth’ refers to a chain with 1 carbon atom and ‘Pent’ refers to a chain with, 5 carbon atoms., , 2. Suffix, The suffix in IUPAC nomenclature is usually a functional group belonging to the molecule which follows, the root of the name. It can be further divided into the following types., •, , A Primary Suffix, which is written immediately after the word root as in the case of alkanes, where, the suffix is ‘ane’.
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•, , A Secondary Suffix, which is generally written after the primary suffix is written. For example,, compounds having an alkane and alcohol group attached to it will be named as an alkanol, with ‘ol’, being the secondary suffix for the alcohol group., , In accordance with these norms, the suffix of a compound can be written as a part of the IUPAC name of the, given compound., , 3. Prefix, Prefixes are added prior to the root of the compounds IUPAC nomenclature. Prefixes are very useful since, they indicate the presence of side chains or substituent groups in the given organic molecule. These prefixes, also offer insight into the cyclic or acyclic natures of the compounds in question., •, , Primary Prefixes Indicate the cyclic or acyclic nature of the given compound. The prefix ‘cyclo’, is used for cyclic compounds, for example., , •, , Secondary Prefixes Indicate the presence of side chains or substituent groups. An example of these, types of prefixes would be the ‘CH3’ group, which is called the methyl group., Thus, prefixes in IUPAC nomenclature can be broadly classified into primary prefixes and secondary, prefixes., , IUPAC Nomenclature Methods, 1. Compositional Nomenclature, Compositional Nomenclature is used to name compounds based on the composition of the species or, substances against systems involving structural information or composition, in accordance with IUPAC, nomenclature., •, , The generalized stoichiometric name is involved in the compositional nomenclature of compounds., Substances are named using multiple prefixes so that the overall stoichiometry of the compound is, made clear from the name., , •, , In cases wherein multiple components are present, the components are divided into two classes –, electronegative components and electropositive components., , •, , These names are similar to the names of salts. However, this does not predict or suggest the, behaviour or chemical nature of the species named in such a way., , •, , The usage of multiple prefixes along with the ordering of components and the usage of the more, electronegative component towards the end of the name must be kept in mind while naming these, compounds via IUPAC norms. An example of such a name for a compound would be the, name phosphorus trichloride used to refer to the compound PCl3, , 2. Substitutive Nomenclature, Substitutive Nomenclature is used in the IUPAC nomenclature of compounds wherein the parent hydride is, altered by the replacement of hydrogen atoms with a substituent group., •, , In this nomenclature system, organic compounds are named with the use of functional groups as the, prefix or suffix to the parent compounds name., , •, , Compounds derived from the hydrides of specific elements can also be named using this method., These elements may also from ring structured or chain structured compounds, , •, , Hydrides that belong to groups 13 to 17 of the modern periodic table are named with the suffix, ‘ane’. Examples of this include Borane, Phosphane, and oxidane, etc.
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An example of the use of substitutive nomenclature can be observed in the usage of the name, Trichlorophosphine to refer to the compound PCl3, , 3. Additive Nomenclature, This method was formulated primarily for its applications in the nomenclature of coordination, compounds. It has a wide range of applications. An example for such nomenclature can be observed in name, Penta-ammine-chloro-cobalt (III) chloride used to describe the coordination compound given by the, chemical formula [CoCl (NH3)5] Cl2., “The prefix ‘chloro’ corresponds to a Chloride, whereas the prefix ‘chlorido’ corresponds to the ligand.”, An example of this nomenclature can be observed in the name tri-chlorido-phosphorus which is used to, describe, the, compound, with, the, formula, PCl3, , IUPAC Nomenclature of a Few Important Aliphatic Compounds, The IUPAC nomenclature of alkanes, alkenes, and alkynes are discussed in the subsections below., , 1. Alkanes, The General formula of alkanes corresponds to CnH2n+2, The suffix ‘ane’ is generally used to describe alkanes. Examples for the nomenclature of alkanes as per, IUPAC guidelines include methane for the compound CH4 and Butane for the compound C4H10, , 2. Alkenes, The General formula of alkenes is described as, CnH2n, The suffix ‘ene’ is used to describe alkenes via, IUPAC norms. Examples for the nomenclature, of alkenes include the name ethene used to, describe the compound given by C2H4 and, Propene used to describe the compound given, by C3H6, , 3. Alkynes, The General formula of alkynes is CnH2n-2, The suffix ‘yne’ is generally used to describe, alkynes. An example of the IUPAC, nomenclature of alkynes is: ethyne used to, describe the compound given by C2H2, , Example of IUPAC Nomenclature, Considering the following Example:
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•, , There exist 9 carbon atoms on the straight chain and the 5th carbon atom (from both ends of the, chain) consists of a substituent group which in turn has 3 carbon atoms in a chain., , •, , Furthermore, there the first and second carbons of this substituent chain have an additional CH, group attached to them., , •, , In the nomenclature of this compound, the 9 membered carbon chain is identified as the parent chain, and is numbered., , •, , The substituent chain attached to position 5 of the parent chain is 3 members long, with 2 methyl, groups attached at positions 1 and 2., , •, , Thus, the carbon chain substituent group on the parent chain can be called 1,2 dimethyl propane., The name for the substituent chain containing this compound would be 1,2 dimethyl propyl., , •, , Substituting this name on the parent chain, the IUPAC name of the compound in question is found, to be: 5-(1,2 dimethyl propyl) nonane., , Isomerism, 1. Structural Isomerism – Structural Isomerism arises due to different arrangement of atoms within, the molecule. Two molecules are structural isomers if they share the same molecular formula., 2. Stereoisomerism – Stereo-isomers are isomeric molecules having the same molecular formula and, the same sequence of bonded atoms, but are only different in the 3D orientations of their atoms in, space. Stereoisomerism may be of two types viz. geometrical (or c\s-trans) isomerism and optical, (or d-1 or mirror-image) isomerism., , Structural Isomerism, Structural isomerism is commonly referred to as constitutional isomerism. The functional groups and the, atoms in the molecules of these isomers are linked in different ways. Different structural isomers are assigned, different IUPAC names since they may or may not contain the same functional group., The different types of structural isomerism are discussed in this subsection., , Chain Isomerism, •, , It is also known as skeletal isomerism., , •, , The components of these isomers display differently branched structures., , •, , Commonly, chain isomers differ in the branching of carbon, , •, , An example of chain isomerism can be observed in the compound C5H12, as illustrated below., , Position Isomerism, •, , The positions of the functional groups or substituent atoms are different in position isomers.
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•, , Typically, this isomerism involves the attachment of the functional groups to different carbon atoms, in the carbon chain., , •, , An example of this type of isomerism can be observed in the compounds having the formula C3H7Cl., , Functional Isomerism, •, , It is also known as functional group isomerism., , •, , As the name suggests, it refers to the compounds that have the same chemical formula but, different functional groups attached to them., , •, , An example of functional isomerism can be observed in the compound C3H6O., , Metamerism, •, , This type of isomerism arises due to the presence of different alkyl chains on each side of the, functional group., , •, , It is a rare type of isomerism and is generally limited to molecules that contain a divalent atom (such, as sulfur or oxygen), surrounded by alkyl groups., , •, , Example: C4H10O can be represented as ethoxyethane (C2H5OC2H5) and methoxy-propane, (CH3OC3H7)., , Tautomerism, •, , A tautomer of a compound refers to the isomer of the compound which only differs in the position, of protons and electrons., , •, , Typically, the tautomers of a compound exist together in equilibrium and easily interchange., , •, , It occurs via an intramolecular proton transfer., , •, , An important example of this phenomenon is Keto-enol tautomerism., , Ring-Chain Isomerism, •, , In ring-chain isomerism, one of the isomers has an open-chain structure whereas the other has a ring, structure., , •, , They generally contain a different number of pi bonds., , •, , A great example of this type of isomerism can be observed in C3H6. Propene and cyclopropane are, the resulting isomers, as illustrated below., , Methods of Purification of Organic Compounds, 1. Simple crystallization – Crystallization is one of the most effective purification techniques for, solids. Simple crystallization involves the selection of the solvent and preparation of the solution., 2. Fractional crystallization – Fractional crystallization is used for the purification of a single, substance contaminated with small quantities of impurities., 3. Sublimation – Sublimation is an excellent method for purifying relatively volatile organic solids, on scales ranging from a few milligrams to tens of grams., 4. Simple distillation – Simple distillation is the process of converting a liquid into its vapour,, transferring the vapour to another place, and recovering the liquid by condensing the vapour.
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5. Fractional distillation – Fractional distillation is the separation procedure of a mixture into sections, or fractions of its material. By heating them to a temperature at which one or more parts of the, mixture vaporize, chemical compounds are isolated., 6. Steam distillation – A steam distillation is simply a distillation in which steam is involved as a, process component. Steam distillation and organic solvent extraction have both been widely used, to extract compounds from spices., 7. Azeotropic distillation – Azeotropic distillation is accomplished by adding to the liquid phase, a, volatile third component that changes the volatility of one of the two components more than the, other so that the components are separated by distillation., 8. Chromatography – The purpose of preparative chromatography is to separate the components of, a mixture for further use (and is thus a form of purification).
