Organic Chemistry: Structures of Organic Compounds, Study notes of Chemistry

Download Organic Chemistry: Structures of Organic Compounds and more Study notes Chemistry in PDF only on Docsity! ORGANIC CHEMISTRY NOTES STRUCTURES OF ORGANIC COMPOUNDS PREPARED BY DEBASISH GANGULY ORGANIC CHEMISTRY: STRUCTURES OF ORGANIC COMPOUNDS 3 chemical bonds. The Lewis structure and chemical formula are two of the most crucial ways to represent a molecule's structure. The number and types of atoms in a molecule are represented informally by the chemical formula, such as H2O for water. The Lewis structure is a more thorough illustration of the molecule that demonstrates the atoms and chemical bonds between them. Two single sigma bonds are visible in the Lewis structure between the hydrogen and oxygen atoms. Additionally, these bonds leave the oxygen atom with two lone electron pairs. The H2O molecule hybridizes as sp3 because it has four hybrid orbitals made up of one s orbital, three p orbitals, and one p orbital. Using a molecule's three-dimensional conformation as a representation of its structure is an essential additional method. The bond angles and torsional angles between atoms determine the conformation of a molecule, which is the spatial arrangement of its atoms. It's crucial to comprehend a molecule's conformation in order to predict its reactivity and solubility. A molecule's structure has a direct impact on its characteristics. For instance, the arrangement of the electrons within a molecule affects its polarity. Polar molecules have a separation of charge, with a slight positive charge on one end and a slight negative charge on the other. ORGANIC CHEMISTRY: STRUCTURES OF ORGANIC COMPOUNDS 4 This polarity has an impact on the molecule's solubility in various solvents and its capacity for hydrogen bonding. A molecule's structure and reactivity are closely related to one another. A molecule's reactivity and the kinds of reactions it can undergo are determined by the functional groups within it, such as - OH, -COOH, and -NH2. A carboxylic acid, for instance, will go through a neutralization reaction with a base, whereas an alcohol will go through an oxidation reaction to form a carbonyl compound. Understanding the interactions between molecules is a crucial part of organic chemistry, in addition to comprehending the structure and characteristics of individual molecules. This includes ideas like chemical equilibria, which describes the balance of reactants and products in a reaction, and intermolecular forces, such as hydrogen bonding and dipole-dipole interactions. Stereochemistry, which examines the three-dimensional arrangements of atoms in a molecule, is another key idea in organic chemistry. Stereoisomers are molecules with different spatial arrangements of atoms but the same chemical formula and bond connectivity. Enantiomers and diastereomers are the two most typical kinds of stereoisomers. Predicting a molecule's reactivity and properties requires an understanding of stereochemistry. The study of reaction mechanisms, which outline the detailed steps involved in a chemical reaction, is also a part of organic chemistry. Foreseeing reaction products and creating synthetic pathways require an understanding of the mechanism of the reaction. In organic chemistry, comprehending the structures and characteristics of molecules is a fundamental idea. While a molecule's properties include its physical and chemical traits like solubility, melting point, and reactivity, its structure refers to how its atoms are arranged and their chemical bonds. Understanding molecular interactions like intermolecular forces and chemical equilibria are crucial because the properties of molecules are closely related to their ORGANIC CHEMISTRY: STRUCTURES OF ORGANIC COMPOUNDS 5 structure. Additionally, designing synthetic pathways and predicting a molecule's reactivity and properties depend on an understanding of reaction mechanisms and stereochemistry. 1.3 Isomerism Chemistry's concept of isomerism describes situations in which two or more compounds share the same molecular formula but have different atomic arrangements. This indicates that although the atoms in the compounds are the same in terms of quantity and type, they are arranged differently in space. Isomerism is significant in organic chemistry because it has an impact on a compound's reactivity as well as its physical and chemical characteristics. There are various kinds of isomers, such as: Structural Isomers: Isomers with a different atomic structure but the same molecular formula is known as structural isomers. For instance, the molecules butane and isobutane, with the molecular formula C4H10, are structural isomers. Stereoisomers: Stereoisomers are isomers that share the same molecular formula and atomic structural arrangement but differ in their atomic spatial arrangements. They go by the name geometric isomers as well. Enantiomers and diastereomers are the two main categories of stereoisomers. Enantiomers are not superimposable and are mirror images of one another. Additionally, they rotate plane- polarized light in opposing directions and are optically active. On the other hand, diastereomers are not identical to one another and are not mirror images of one another. Constitutional isomers: Although the atoms in these isomers are connected differently, they have the same molecular formula. They go by the name skeletal isomers as well. Tautomers: Although these isomers share the same molecular structure, they have various functional groups. They go by the name ORGANIC CHEMISTRY: STRUCTURES OF ORGANIC COMPOUNDS 8 naming compounds:  Identify the longest continuous carbon chain in the compound. This is known as the parent chain.  Number the carbon atoms in the parent chain, beginning at the end closest to a functional group.  Identify the functional groups present in the compound, such as alcohols, carboxylic acids, or alkanes.  Based on the functional groups, name the compound using the appropriate prefixes and suffixes.  In case of multiple functional groups, the name of the compound is determined by the highest priority functional group.  If there are two or more of the same functional groups, use prefixes such as di, tri, etc.  Use of commas, hyphens, and brackets to indicate the position of substituents in the compound. For instance, propanoic acid would be the name given to the compound CH3CH2CH2COOH. Propanoic acid is named as such because it contains a carboxylic acid functional group and has the longest continuous chain with three carbons. It is a molecule with a carboxylic acid functional group (-COOH) and a hydrocarbon chain with 3 carbon atoms (CH3CH2CH2). The molecular formula of CH3CH2CH2COOH is C4H8O2. If the parent chain has several branches or substituents, they are ORGANIC CHEMISTRY: STRUCTURES OF ORGANIC COMPOUNDS 9 known as alkyl or other pertinent groups and are denoted by prefixes like methyl, ethyl, propyl, etc. For instance, the name 3-methylbutanoic acid would be given to the compound CH3CH2CH(CH3) CH2COOH. In this case, 3-methyl denotes the presence of a methyl group attached to the third carbon atom in the parent chain, while butanoic denotes the presence of a carboxylic acid functional group. Because the longest continuous chain in this compound has four carbons, it is called 3-methylbutanoic acid. The molecule has a carboxylic acid functional group (-COOH) and a hydrocarbon chain with 5 carbon atoms and one methyl group (CH3) at the 3rd position. The structural formula of CH3CH2CH(CH3) CH2COOH is H3C-CH2-CH-CH3-CH-COOH. Note that this is a branched alkanoic acid and the methyl group is attached to the 3rd carbon. When it comes to cyclic compounds, the parent chain is the one with the most substituents and is numbered so that the substituents are in the lowest numbers possible. For instance, the name 2-ethyl-1-cyclobutane would be given to the compound CH3CH2CH(CH3) CCH3. Here, 2-ethyl indicates that the second carbon atom in the cyclic parent chain has an ethyl group attached to it, while 1-cyclobutane denotes the presence of a cyclic parent chain with four carbons. These are the basic rules for the IUPAC nomenclature of organic compounds, and there may be some variations depending on the specific compound and the nature of the functional groups present in it. The name for the substance CH3CH2C(CH3) CH(CH3) CH2OH is 2-ethyl-3,4-dimethyl-1-hexanol. The parent chain, which is the longest continuous carbon chain in this instance, is number six, and alcohol is the functional group, as denoted by the -ol suffix. The parent chain's second carbon atom has an ethyl group attached, and its third and ORGANIC CHEMISTRY: STRUCTURES OF ORGANIC COMPOUNDS 10 fourth carbon atoms each have two methyl groups, according to the prefixes 2,4-dimethyl and 3,4-ethyl. The compound CH3CH2CH(CH3) C(O)C(CH3) CH3 would be named as 2-ethyl-3-methyl-3-propoxybutane. Here, the longest continuous carbon chain is 4, which is the parent chain, and the functional group is ether, indicated by the -oxy prefix. The 2-ethyl and 3-methyl prefixes indicate that an ethyl group is attached to the second carbon atom and a methyl group is attached to the 3rd carbon atom of the parent chain. The name 2-methylpropanoic acid would be given to the compound CH3CH(COOH)C(CH3) C(CH2) CH3. Here, the functional group is a carboxylic acid, denoted by the suffix -oic acid, and the longest continuous carbon chain is 5, which is the parent chain. The 2-methyl prefix denotes the presence of a methyl group on the parent chain's second carbon atom. The name for the substance CH3CH2C(CH3) CH(C(=O) NH2) CH2CH3 is 2-ethyl-3,4-dimethyl-1-aminohexane. Here, the functional group is an amine, denoted by the suffix -amine, and the longest continuous carbon chain is 6, which is the parent chain. The parent chain's second carbon atom has an ethyl group attached, and its third and fourth carbon atoms each have two methyl groups, according to the prefixes 2,4-dimethyl and 3,4-ethyl. 2-Ethyl-3,4-dimethyl-1-formylhexane is the name given to the compound CH3CH2C(CH3) CH(C(=O) OCH3) CH2CH3. The functional group in this instance is an aldehyde, denoted by the -al suffix, and the longest continuous carbon chain is 6, which is also known as the parent chain. The parent chain's second carbon atom has an ethyl group attached, and its third and fourth carbon atoms each have two methyl groups, according to the prefixes 2,4-dimethyl and 3,4-ethyl. It is crucial to remember that the IUPAC system is not always the only or most popular way to name a compound, particularly when it ORGANIC CHEMISTRY: STRUCTURES OF ORGANIC COMPOUNDS 13  IUPAC nomenclature provides a standardized and consistent way to name compounds, allowing for clear communication and easy identification of compounds in research and industry.  The IUPAC system helps in understanding the structure of the compound, the functional group present, and the reactivity of the molecule.  The parent hydrocarbon is named based on the number of carbon atoms in the chain.  Functional groups are specific groups of atoms within a molecule that are responsible for the chemical properties and reactivity of the molecule.  The presence of a functional group in a molecule gives it specific chemical properties and reactivity.  Understanding the role of functional groups in organic chemistry is crucial for understanding the reactivity and properties of organic compounds, as well as for predicting and controlling chemical reactions. QUESTION TIME I. Multiple-Choice Questions 1. What types of isomers have the same structural arrangement of atoms but different spatial arrangements of atoms? a) Structural isomers b) Stereoisomers c) Constitutional isomers d) Tautomers 2. What types of isomers have the same molecular formula but different structural arrangements of atoms? a) Structural isomers b) Stereoisomers ORGANIC CHEMISTRY: STRUCTURES OF ORGANIC COMPOUNDS 14 c) Constitutional isomers d) Tautomers 3. What types of isomers have the same molecular formula but different functional groups? a) Structural isomers b) Stereoisomers c) Constitutional isomers d) Tautomers 4. What types of isomers have the same molecular formula and bond connectivity but different arrangements of atoms in space? a) Structural isomers b) Stereoisomers c) Constitutional isomers d) Tautomers 5. What types of isomers have the same molecular formula but different connectivity of atoms? a) Structural isomers b) Stereoisomers c) Constitutional isomers d) Tautomers 6. What type of isomers are mirror images of each other? a) Structural isomers b) Enantiomers c) Diastereomers d) Constitutional isomers 7. What types of isomers are non-identical? a) Structural isomers b) Enantiomers c) Diastereomers d) Constitutional isomers 8. What type of isomers rotate plane-polarized light in opposite directions? ORGANIC CHEMISTRY: STRUCTURES OF ORGANIC COMPOUNDS 15 a) Structural isomers b) Enantiomers c) Diastereomers d) Constitutional isomers 9. What types of isomers is non-superimposable? a) Structural isomers b) Enantiomers c) Diastereomers d) Constitutional isomers 10. What is the systematic naming of organic compounds according to specific rules and conventions called? a) Structural nomenclature b) Isomeric nomenclature c) Functional nomenclature d) IUPAC nomenclature 11. What is the most widely used and recognized system of nomenclature in organic chemistry? a) Common name system b) Functional class system c) IUPAC system d) Structural class system 12. What is the longest continuous chain of carbon atoms within a molecule called? a) Parent hydrocarbon b) Functional group c) Substituent d) Isomeric chain 13. What is the parent hydrocarbon named based on? a) The number of carbon atoms in the chain b) The number of functional groups present c) The number of substituents present d) The spatial arrangements of atoms ORGANIC CHEMISTRY: STRUCTURES OF ORGANIC COMPOUNDS 18 b) Alkynes c) Alkanes d) Arenes (Answer: c) 26. What type of compound contains an aromatic ring? a) Alkenes b) Alkynes c) Alkanes d) Arenes 27. What type of compound contains a carbon-carbon bond and a carbon-oxygen bond? a) Alkenes b) Alkynes c) Alkanes d) Esters 28. What type of compound contains a carbon-carbon bond and a carbon-nitrogen bond? a) Amides b) Amines c) Nitriles d) both (a) and (b) 29. What type of compound contains a carbon-carbon bond and a carbon-hydrogen bond? a) Hydrocarbons b) Inorganic compounds c) Organic compounds d) both (a) and (c) 30. What type of compound contains a carbon-carbon bond and a carbon-halogen bond? a) Alkyl halides b) Halocarbons c) Organohalides d) both (a) and (b) ORGANIC CHEMISTRY: STRUCTURES OF ORGANIC COMPOUNDS 19 31. What type of compound contains a carbon-carbon bond and a carbon-metal bond? a) Organometallics b) Inorganic compounds c) Organic compounds d) both (a) and (b) 32. What type of bond is formed when two carbon atoms share electrons? a) Covalent bond b) Ionic bond c) Hydrogen bond d) Metallic bond 33. What type of chemical reaction results in the formation of a new molecule? a) Synthesis reaction b) Decomposition reaction c) Neutralization reaction d) Oxidation reaction 34. What type of chemical reaction results in the breaking down of a molecule into simpler compounds or elements? a) Synthesis reaction b) Decomposition reaction c) Neutralization reaction d) Oxidation reaction 35. What type of chemical reaction results in the transfer of electrons from one molecule to another? a) Synthesis reaction b) Decomposition reaction c) Redox reaction d) Neutralization reaction 36. What is the study of the chemical and physical properties of compounds and their interactions with the environment called? ORGANIC CHEMISTRY: STRUCTURES OF ORGANIC COMPOUNDS 20 a) Organic chemistry b) Biochemistry c) Analytical chemistry d) Environmental chemistry 37. What is the study of the chemical reactions and processes that occur in the natural environment called? a) Organic chemistry b) Biochemistry c) Analytical chemistry d) Environmental chemistry II. Short Answer type Questions 1. What types of isomers have the same structural arrangement of atoms but different spatial arrangements of atoms? 2. What types of isomers have the same molecular formula but different structural arrangements of atoms? 3. What types of isomers have the same molecular formula but different functional groups? 4. What types of isomers have the same molecular formula and bond connectivity but different arrangements of atoms in space? 5. What type of isomers have the same molecular formula but different connectivity of atoms? 6. What type of isomers are mirror images of each other? 7. What type of isomers are non-identical? 8. What type of isomers rotate plane-polarized light in opposite directions? ORGANIC CHEMISTRY: STRUCTURES OF ORGANIC COMPOUNDS 23 how do they affect the properties and reactivity of a molecule? ANSWERS TO THE QUESTION TIME I. Multiple-Choice Questions 1. b) Stereoisomers 2. a) Structural isomers 3. d) Tautomers 4. b) Stereoisomers 5. c) Constitutional isomers 6. b) Enantiomers 7. c) Diastereomers 8. b) Enantiomers 9. b) Enantiomers 10. d) IUPAC nomenclature 11. c) IUPAC system 12. a) Parent hydrocarbon 13. a) The number of carbon atoms in the chain 14. c) Its conformation 15. a) The distribution of electrons within the molecule 16. a) Substitution reaction 17. b) Elimination reaction 18. b) Biochemistry 19. c) Medicinal chemistry 20. d) Both (a) and (c) 21. c) Carboxylic acids 22. d) Both (a) and (b) 23. b) Alkynes 24. a) Alkenes 25. c) Alkanes 26. d) Arenes ORGANIC CHEMISTRY: STRUCTURES OF ORGANIC COMPOUNDS 24 27. d) Esters 28. a) Amides 29. a) Hydrocarbons 30. d) both (a) and (b) 31. a) Organometallics 32. a) Covalent bond 33. a) Synthesis reaction 34. b) Decomposition reaction 35. c) Redox reaction 36. c) Analytical chemistry 37. d) Environmental chemistry II. Short Answer type Questions 1. Stereoisomers 2. Structural isomers 3. Tautomers 4. Stereoisomers 5. Constitutional isomers 6. Enantiomers 7. Diastereomers 8. Enantiomers 9. Enantiomers 10. IUPAC nomenclature 11. IUPAC system 12. Parent hydrocarbon 13. The number of carbon atoms in the chain 14. Its conformation 15. The distribution of electrons within the molecule 16. Substitution reaction 17. Elimination reaction 18. Biochemistry 19. Medicinal chemistry ORGANIC CHEMISTRY: STRUCTURES OF ORGANIC COMPOUNDS 25 20. Organic compounds and Hydrocarbons 21. Covalent bond 22. Synthesis reaction 23. Decomposition reaction 24. Redox reaction 25. Analytical Chemistry 26. Environmental Chemistry 27. Hydrocarbons 28. Neutralization reaction 29. Oxidation reaction 30. Constitutional isomers III. Long Answer Type Questions 1. Isomers are molecules that have the same molecular formula but different structural arrangements of atoms. There are several types of isomers, including structural isomers, which have the same molecular formula but different structural arrangements of atoms, stereoisomers, which have the same structural arrangement of atoms but different spatial arrangements of atoms, constitutional isomers, which have the same molecular formula but different connectivity of atoms, and tautomers, which have the same molecular formula but different functional groups. 2. IUPAC (International Union of Pure and Applied Chemistry) nomenclature is the systematic naming of organic compounds according to specific rules and conventions. It is important in organic chemistry because it provides a standardized and consistent way to name compounds, which allows for clear communication and easy identification of compounds in research and industry. Additionally, the IUPAC system helps in understanding the structure of the compound, the functional group present, and the reactivity