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This document provides an introduction to hydrocarbons, which are organic compounds composed of hydrogen and carbon. It discusses the characteristics of hydrocarbons and defines different types including aliphatic hydrocarbons (alkanes, alkenes, alkynes), aromatic hydrocarbons, and introduces chemical bonding concepts like ionic bonds, covalent bonds, and coordinate covalent bonds. It provides examples and properties of different hydrocarbon groups and bond types.
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- 2. Course title: organic chemistry course code: chem-1204 session:2019-21 Andleeb Tariq Visiting Lecturer Govt. College Mirpur ajk
- 4. HYDROCARBONS: • A hydrocarbon is an organic chemical compound composed exclusively of hydrogen and carbon atoms. Hydrocarbons are naturally-occurring compounds and form the basis of crude oil, natural gas, coal, and other important energy sources. • Hydrocarbons are highly combustible and produce carbon dioxide, water, and heat when they are burned. Therefore, hydrocarbons are highly effective as a source of fuel.
- 5. • Characteristics of organic compounds • All organic compounds have the following characteristic properties • 1. Many organic compounds are flammable • 2. They are mostly covalent compounds • 3. They are generally soluble in non - polar solvents like carbon tetrachloride, benzene etc. • 4. They have generally low boiling point and melting point. • 5. They exhibit isomerism
- 7. • Hydrocarbons themselves are separated into two types: aliphatic hydrocarbons and aromatic hydrocarbons. Aliphatic hydrocarbon are hydrocarbons based on chains of C atoms. There are three types of aliphatic hydrocarbons. • Alkanes are aliphatic hydrocarbons with only single covalent bonds. • Alkenes are aliphatic hydrocarbons that contain at least one C–C double bond. • Alkynes are aliphatic hydrocarbons that contain a C–C triple bond. Occasionally, we find an aliphatic hydrocarbon with a ring of C atoms; these hydrocarbons are called cycloalkanes (or cycloalkenes or cycloalkynes)
- 8. • Aliphatic hydrocarbon: It is an Open chain hydrocarbon that is odourless. It is categorised into two groups- Aliphatic hydrocarbon may further be divided into groups- Saturated hydrocarbon or Alkane or Paraffin; Unsaturated hydrocarbon
- 9. Saturated hydrocarbons: • Saturated hydrocarbon or Alkane or Paraffin: This is also called alkane or paraffin. • Paraffin is a Latin word, which implies- less active and because of lesser activities of saturated hydrocarbons, these are called paraffin. • The general formula of the member series of saturated hydrocarbons is given by CnH2n+2; • where n is the number of members of the series. The organic compounds like methane, ethane, propane, butane, pentane, etc are saturated hydrocarbons in which all carbon atoms are attached with a single covalent bond to each other.
- 11. Unsaturated hydrocarbons: • Unsaturated hydrocarbon: Those compounds of aliphatic hydrocarbons in which carbon atoms have double or triple covalent bonds called unsaturated hydrocarbons. • This is also of two types- Alkenes or Olefin; Acetylene hydrocarbon or alkynes. • a) Alkenes or Olefin: Those compounds of unsaturated aliphatic hydrocarbon in which carbon atoms have double covalent bond called Ethylene hydrocarbons or olefin or alkenes. General formula for the members of this series is CnH2n. The organic compound Ethylene (C2H4) is the example of alkenes.
- 12. Unsaturated hydrocarbons • b) Acetylene hydrocarbon or alkynes: Those compounds of unsaturated aliphatic hydrocarbon in which carbon atoms have triple covalent bond are called acetylene or alkynes. • General formula for the members of this series is CnH2n_2. • The organic compound acetylene (C2H2) is the simplest example of this hydrocarbon.
- 13. Aromatic Hydrocarbons: • Aromatic hydrocarbon: It is closed chain hydrocarbon which has a special type of smell (odour). • Those compounds of hydrocarbon which are composed from hydrogen and carbon and have the branches like benzene, called aromatic hydrocarbons. • General formula of the members of this series is CnH2n-2. • There are various compounds like benzene; toluene, napthalene, anthracene etc are examples of aromatic hydrocarbon in which benzene is the simplest one. Sometimes aromatic hydrocarbons are also called Arenes.
- 14. Chemical Bonding
- 15. Chemical Bonding Bond : The force which hold atoms together in the molecule are described by the word Bond. Before the consideration of the electronic structure of atoms, the nature of forces binding atoms together to form molecules were considered to be due to their combining capacity called Valencies . Thus the valency was considered as the number of valence bonds formed by an atom of one element with other atoms. A stable molecule is a group of atoms held together by valence forces.
- 16. Nature and types of Chemical Bond • Ionic Bond or Electrovalent Bond • Covalent Bond or Electron pair Bond • Coordinate-covalent Bond Ionic Bond or Electrovalent bond: The bond formed by complete transfer of electrons from electropositive atom to more electronegative atom is called ionic or electrovalent bond. This type of bond is exhibited by atoms which can either lose electrons to form positively charged ions or gain electrons to form negatively charged ions. The two atoms are held together by electrostatic forces of attraction acting between such atoms.
- 17. Characteristics features of ionic compounds: The strong coulomb forces existing between ions in such compounds render special properties to them. These properties are: • High boiling and melting points : Because of the strong attractive forces ionic solids would be expected to have high melting and boiling points . These forces are distributed among all the ions of solid .e.g . NaCl boils at 1470 but a covalent compound boils at 77. • Electrical conductivity : The molten salts of ionic compounds are good conductors of electricity because cations and anions are free to move under the influence of electric field. • Solubility in polar solvents: Ionic solids tend to be soluble in polar solvents . Non polar solvents do not affect the ionic solids and would not be able to dissolve them. • Crystalline states: Ionic compounds are composed of clusters of ions in the crystal lattice and form definite structure or crystal shapes. • Isomorphism: Ionic crystals having the same crystalline structures are found to have identical electronic arrangements . • Dielectric constant: The ionic compounds show high values of dielectric constant. • Non directional bonds : ionic bonds are non directional
- 18. COVALENT OR ELECTRON PAIR BOND: The formation of a covalent bond involves the mutual sharing of pair of electrons between two atoms , each atom contributing one electron to the pair. For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full outer shell, corresponding to a stable electronic configuration. In organic chemistry, covalent bonds are much more common than ionic bonds
- 19. Types of Covalent Bond • Single covalent bond : formed by mutual sharing of one electron. • Double covalent bond: formed by mutual sharing of two electrons. • Triple covalent bond: formed by mutual sharing of three electrons.
- 20. Characteristic features of covalent: • Low melting and boiling points: Covalent compounds consist of molecules held by weak forces. These can be easily overcome by heat. Thus, covalent compounds have low melting points and low boiling points. • Non-conducting nature: Covalent compounds do not conduct electricity, i.e., electricity does not pass through the covalent compounds. This is because the covalent compounds do not contain ions, or free electrons. Sugar is a covalent compound, and its solution does not conduct electricity. Solutions of polar covalent compounds, e.g., HCl, conduct electricity due to the presence of ions in solutions. • Solubility: Covalent compounds are usually insoluble not polar solvents like water. The covalent compounds however, dissolve in non-polar solvents, like benzene, toluene, etc. • Slow rate of reaction : the reactions of the covalent compounds are quite slow. This is because the covalent compounds take part in reactions as molecules, and the molecular reactions are slow. • Isomerism: Covalent bonds are rigid and directional. Therefore, these can give different arrangements of atoms in space. So, a single molecular formula may represent a number of different compounds with different properties. This phenomenon is called isomerism
- 21. Comparison of ionic and covalent bond • An ionic bond essentially donates an electron to the other atom participating in the bond, while electrons in a covalent bond are shared equally between the atoms. • The only pure covalent bonds occur between identical atoms. Usually, there is some polarity (polar covalent bond) in which the electrons are shared, but spend more time with one atom than the other. • Ionic bonds form between a metal and a nonmetal. Covalent bonds form between two nonmetals.
- 22. Coordinate- Covalent Bond In a formation of a dative bond, other atom does not provide electron for sharing. It is one-sided sharing. The formation of the coordinate covalent bond belongs to the atoms that have lone pairs of electrons. the contributions of electrons towards combining the atoms in a covalent bond are generally equal. The atom that provides electron pair is termed as Donor and the other which takes the electron pair is called Acceptor. Representation: Dative bond is represented by an arrowhead that points from donor atom to the acceptor.
- 23. Coordinate -covalent Bond • Reaction between ammonia and boron trifluoride Boron trifluoride is a compound that does not have a noble gas structure around the boron atom . The boron only has three pairs of electrons in its bonding level, whereas there would be room for four pairs. BF3 is described as being electron deficient. The lone pair on the nitrogen of an ammonia molecule can be used to overcome that deficiency, and a compound is formed involving a coordinate bond.
- 24. • Characteristics of co-ordinate covalent compound • Their melting and boiling points are higher than purely covalent compounds and lower than purely ionic compounds. • These are sparingly soluble in polar solvent like water but readily soluble in non-polar solvents. • Like covalent compounds, these are also bad conductors of electricity. Their solutions or fused masses do not allow the passage to electricity. • The bond is rigid and directional. Thus, coordinate compounds show isomerism.
- 25. Course Title: Organic Chemistry Course code:CHEM-1204 Session:2019-23 Credit hours: 3+1
- 26. Chemical Bonding Bond : The force which hold atoms together in the molecule are described by the word Bond. Before the consideration of the electronic structure of atoms, the nature of forces binding atoms together to form molecules were considered to be due to their combining capacity called Valencies . Thus the valency was considered as the number of valence bonds formed by an atom of one element with other atoms. A stable molecule is a group of atoms held together by valence forces.
- 27. Nature and types of Chemical Bond • Ionic Bond or Electrovalent Bond • Covalent Bond or Electron pair Bond • Coordinate-covalent Bond Ionic Bond or Electrovalent bond: The bond formed by complete transfer of electrons from electropositive atom to more electronegative atom is called ionic or electrovalent bond. This type of bond is exhibited by atoms which can either lose electrons to form positively charged ions or gain electrons to form negatively charged ions. The two atoms are held together by electrostatic forces of attraction acting between such atoms.
- 28. Characteristics features of ionic compounds: The strong coulomb forces existing between ions in such compounds render special properties to them. These properties are: • High boiling and melting points : Because of the strong attractive forces ionic solids would be expected to have high melting and boiling points . These forces are distributed among all the ions of solid .e.g . NaCl boils at 1470 but a covalent compound boils at 77. • Electrical conductivity : The molten salts of ionic compounds are good conductors of electricity because cations and anions are free to move under the influence of electric field. • Solubility in polar solvents: Ionic solids tend to be soluble in polar solvents . Non polar solvents do not affect the ionic solids and would not be able to dissolve them. • Crystalline states: Ionic compounds are composed of clusters of ions in the crystal lattice and form definite structure or crystal shapes. • Isomorphism: Ionic crystals having the same crystalline structures are found to have identical electronic arrangements . • Dielectric constant: The ionic compounds show high values of dielectric constant. • Non directional bonds : ionic bonds are non directional
- 29. COVALENT OR ELECTRON PAIR BOND: The formation of a covalent bond involves the mutual sharing of pair of electrons between two atoms , each atom contributing one electron to the pair. For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full outer shell, corresponding to a stable electronic configuration. In organic chemistry, covalent bonds are much more common than ionic bonds
- 30. Types of Covalent Bond • Single covalent bond : formed by mutual sharing of one electron. • Double covalent bond: formed by mutual sharing of two electrons. • Triple covalent bond: formed by mutual sharing of three electrons.
- 31. Characteristic features of covalent: • Low melting and boiling points: Covalent compounds consist of molecules held by weak forces. These can be easily overcome by heat. Thus, covalent compounds have low melting points and low boiling points. • Non-conducting nature: Covalent compounds do not conduct electricity, i.e., electricity does not pass through the covalent compounds. This is because the covalent compounds do not contain ions, or free electrons. Sugar is a covalent compound, and its solution does not conduct electricity. Solutions of polar covalent compounds, e.g., HCl, conduct electricity due to the presence of ions in solutions. • Solubility: Covalent compounds are usually insoluble not polar solvents like water. The covalent compounds however, dissolve in non-polar solvents, like benzene, toluene, etc. • Slow rate of reaction : the reactions of the covalent compounds are quite slow. This is because the covalent compounds take part in reactions as molecules, and the molecular reactions are slow. • Isomerism: Covalent bonds are rigid and directional. Therefore, these can give different arrangements of atoms in space. So, a single molecular formula may represent a number of different compounds with different properties. This phenomenon is called isomerism
- 32. Comparison of ionic and covalent bond • An ionic bond essentially donates an electron to the other atom participating in the bond, while electrons in a covalent bond are shared equally between the atoms. • The only pure covalent bonds occur between identical atoms. Usually, there is some polarity (polar covalent bond) in which the electrons are shared, but spend more time with one atom than the other. • Ionic bonds form between a metal and a nonmetal. Covalent bonds form between two nonmetals.
- 33. Coordinate- Covalent Bond In a formation of a dative bond, other atom does not provide electron for sharing. It is one-sided sharing. The formation of the coordinate covalent bond belongs to the atoms that have lone pairs of electrons. the contributions of electrons towards combining the atoms in a covalent bond are generally equal. The atom that provides electron pair is termed as Donor and the other which takes the electron pair is called Acceptor. Representation: Dative bond is represented by an arrowhead that points from donor atom to the acceptor.
- 34. Coordinate -covalent Bond • Reaction between ammonia and boron trifluoride Boron trifluoride is a compound that does not have a noble gas structure around the boron atom . The boron only has three pairs of electrons in its bonding level, whereas there would be room for four pairs. BF3 is described as being electron deficient. The lone pair on the nitrogen of an ammonia molecule can be used to overcome that deficiency, and a compound is formed involving a coordinate bond.
- 35. • Characteristics of co-ordinate covalent compound • Their melting and boiling points are higher than purely covalent compounds and lower than purely ionic compounds. • These are sparingly soluble in polar solvent like water but readily soluble in non-polar solvents. • Like covalent compounds, these are also bad conductors of electricity. Their solutions or fused masses do not allow the passage to electricity. • The bond is rigid and directional. Thus, coordinate compounds show isomerism.
- 36. Course Title: Organic Chemistry Course code:CHEM-1204 Session:2019-23 Credit hours: 3+1
- 37. Chemical Bonding Bond : The force which hold atoms together in the molecule are described by the word Bond. Before the consideration of the electronic structure of atoms, the nature of forces binding atoms together to form molecules were considered to be due to their combining capacity called Valencies . Thus the valency was considered as the number of valence bonds formed by an atom of one element with other atoms. A stable molecule is a group of atoms held together by valence forces.
- 38. Nature and types of Chemical Bond • Ionic Bond or Electrovalent Bond • Covalent Bond or Electron pair Bond • Coordinate-covalent Bond Ionic Bond or Electrovalent bond: The bond formed by complete transfer of electrons from electropositive atom to more electronegative atom is called ionic or electrovalent bond. This type of bond is exhibited by atoms which can either lose electrons to form positively charged ions or gain electrons to form negatively charged ions. The two atoms are held together by electrostatic forces of attraction acting between such atoms.
- 39. Characteristics features of ionic compounds: The strong coulomb forces existing between ions in such compounds render special properties to them. These properties are: • High boiling and melting points : Because of the strong attractive forces ionic solids would be expected to have high melting and boiling points . These forces are distributed among all the ions of solid .e.g . NaCl boils at 1470 but a covalent compound boils at 77. • Electrical conductivity : The molten salts of ionic compounds are good conductors of electricity because cations and anions are free to move under the influence of electric field. • Solubility in polar solvents: Ionic solids tend to be insoluble in polar solvents . Non polar solvents do not affect the ionic solids and would not be able to dissolve them. • Crystalline states: Ionic compounds are composed of clusters of ions in the crystal lattice and form definite structure or crystal shapes. • Isomorphism: Ionic crystals having the same crystalline structures are found to have identical electronic arrangements . • Dielectric constant: The ionic compounds show high values of dielectric constant. • Non directional bonds : ionic bonds are non directional
- 40. COVALENT OR ELECTRON PAIR BOND: The formation of a covalent bond involves the mutual sharing of pair of electrons between two atoms , each atom contributing one electron to the pair. For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full outer shell, corresponding to a stable electronic configuration. In organic chemistry, covalent bonds are much more common than ionic bonds
- 41. Types of Covalent Bond • Single covalent bond : formed by mutual sharing of one electron. • Double covalent bond: formed by mutual sharing of two electrons. • Triple covalent bond: formed by mutual sharing of three electrons.
- 42. Characteristic features of covalent: • Low melting and boiling points: Covalent compounds consist of molecules held by weak forces. These can be easily overcome by heat. Thus, covalent compounds have low melting points and low boiling points. • Non-conducting nature: Covalent compounds do not conduct electricity, i.e., electricity does not pass through the covalent compounds. This is because the covalent compounds do not contain ions, or free electrons. Sugar is a covalent compound, and its solution does not conduct electricity. Solutions of polar covalent compounds, e.g., HCl, conduct electricity due to the presence of ions in solutions. • Solubility: Covalent compounds are usually insoluble not polar solvents like water. The covalent compounds however, dissolve in non-polar solvents, like benzene, toluene, etc. • Slow rate of reaction : the reactions of the covalent compounds are quite slow. This is because the covalent compounds take part in reactions as molecules, and the molecular reactions are slow. • Isomerism: Covalent bonds are rigid and directional. Therefore, these can give different arrangements of atoms in space. So, a single molecular formula may represent a number of different compounds with different properties. This phenomenon is called isomerism
- 43. Comparison of ionic and covalent bond • An ionic bond essentially donates an electron to the other atom participating in the bond, while electrons in a covalent bond are shared equally between the atoms. • The only pure covalent bonds occur between identical atoms. Usually, there is some polarity (polar covalent bond) in which the electrons are shared, but spend more time with one atom than the other. • Ionic bonds form between a metal and a nonmetal. Covalent bonds form between two nonmetals.
- 44. Coordinate- Covalent Bond In a formation of a dative bond, other atom does not provide electron for sharing. It is one-sided sharing. The formation of the coordinate covalent bond belongs to the atoms that have lone pairs of electrons. the contributions of electrons towards combining the atoms in a covalent bond are generally equal. The atom that provides electron pair is termed as Donor and the other which takes the electron pair is called Acceptor. Representation: Dative bond is represented by an arrowhead that points from donor atom to the acceptor.
- 45. Coordinate -covalent Bond • Reaction between ammonia and boron trifluoride Boron trifluoride is a compound that does not have a noble gas structure around the boron atom . The boron only has three pairs of electrons in its bonding level, whereas there would be room for four pairs. BF3 is described as being electron deficient. The lone pair on the nitrogen of an ammonia molecule can be used to overcome that deficiency, and a compound is formed involving a coordinate bond.
- 46. • Characteristics of co-ordinate covalent compound • Their melting and boiling points are higher than purely covalent compounds and lower than purely ionic compounds. • These are sparingly soluble in polar solvent like water but readily soluble in non-polar solvents. • Like covalent compounds, these are also bad conductors of electricity. Their solutions or fused masses do not allow the passage to electricity. • The bond is rigid and directional. Thus, coordinate compounds show isomerism.
- 48. LOCALIZED AND DELOCALIZED TYPES OF BONDIND Chemical bonds are formed when two nuclei share a pair of electrons between them .These bonds are considered combinations of overlapping one-electron atomic orbitals .The bond is strongest when two electrons are confined to a region between the two nuclei .This type of bond is described as a localized bond . Delocalized bonding electrons are electrons in a molecule , ion or solid metal that are not associated with a single atom or a covalent bond. For example , in Benzene molecule , the delocalization of electrons is indicated by circle. A molecule with delocalized bonding is more stable than a molecule with localized bonding.
- 51. What are Localized Chemical Bonds? Localized chemical bonds are normal sigma and pi bonds or lone electron pairs that exist on a single atom. These bonds are concentrated on a limited region of a molecule. These regions have a concentrated electron distribution. In other words, the electron density of this region is very high. A localized bond forms when two molecular orbitals of two separate atoms overlap with each other. Sigma bonds may form due to the overlap of two s orbitals, two p orbitals or s-p overlap
- 52. What are Delocalized Chemical Bonds? Delocalized chemical bonds are the chemical bonds that do not associate with only a single atom but with several atoms or other chemical bonds. We call the electrons in these bonds as ‘delocalized electrons’. Delocalization occurs in the conjugated pi system. A conjugated pi system has double bonds and single bonds in an alternating pattern.
- 53. For example, the benzene ring has three single bonds and three double bonds in an alternating pattern. Each carbon atom in this ring has a p orbital that does not undergo frontal overlapping. Therefore these p orbitals can have side overlapping. This kind of overlapping is the delocalization. We can indicate this as two circles on the top of the benzene ring and the bottom of the ring. These electrons are free to move throughout the molecule because they do not have a permanent binding to a single atom or a covalent bond.
- 54. What is the Difference Between Localized and Delocalized Chemical Bonds? Localized chemical bonds are normal sigma and pi bonds or lone electron pairs that exists on a single atom. These bonds form due to frontal overlapping between s orbitals, p orbitals or s and p orbitals. Moreover, these electrons are limited to a particular region between two separate atoms. Delocalized chemical bonds are the chemical bonds that do not associate with only a single atom but with several atoms or other chemical bonds. These bonds have electrons spread throughout the molecule that are free to move. These bonds form due to side overlapping of p orbitals. This is the main difference between localized and delocalized chemical bonds.
- 56. Summary Localized vs Delocalized Chemical Bonds A chemical bond is a connection between two atoms. There are two forms of chemical bonds as localized and delocalized chemical bonds. The difference between localized and delocalized chemical bonds is that a localized chemical bond is a specific bond or a lone electron pair on a specific atom whereas a delocalized chemical bond is a specific bond that is not associated with a single atom or a covalent bond.
- 57. Hybridization: The hypothetical process of mixing of two or more pure atomic orbital from nearly equal energy to give equal number of hybrid orbital. The orbitals formed are called hybrid orbitals. •RULES: •Only orbital of similar energy belong to same atom or ions can hybridize together. •Number of hybridized orbital produced is equal to the number of orbitals undergoing hybridization. •Hybrid bond are stronger than single non-hybridized bonds of compounds . •Most of hybridized orbitals are similar but they are not necessary identical in shape . They differ from one another in orientation in space. •From the type of hybridization one can predict the geometry and bond angles of molecules. •An orbital which has been use to built up a hybrid orbital is no longer available to whole electron in its pure form.
- 61. • The purpose of hybridization is to see the types of bonds that the atoms share with each other, whether it be sigma or pi bonds. The different types of bonds allow different properties, like how pi bonds do not allow rotation whereas sigma bonds are rotational. Hybrid orbitals are mixtures of atomic orbitals in various proportions. • For example, the hybrid orbitals on the C atom of methane consist of one- fourth s character and three-fourths p character. • We say they are sp3 ("s-p-three") hybridized.
- 62. • The four new hybridized orbitals have both s and p character. • The dumbbell shape reflects the p character and the big lobe is nearly spherical like an s orbital. • The new orbitals all have the same energy but they point in different directions (towards the corners of a tetrahedron). • This leads to the most stable molecules when the C atom forms bonds to four other The concept of hybridization was introduced because it was the best explanation for the fact that all the C - H bonds in molecules like methane are identical. Example In their ground state, carbon atoms naturally have electron configuration 1s2 2s2 2p2. The four outermost electrons, i.e. those in the 2s and 2p sublevels are available to form chemical bonds with other atoms. The 2s orbital is capable of holding up to two electrons, and there are three 2p orbitals, each capable of holding up to two electrons, which means the 2p orbitals can hold up to six electrons. Individually, these electron orbitals look something like this. (Each is centered on carbon's nucleus and the p orbitals make angles of 90° with one another.)
- 63. • Key Features of Hybridization • Atomic orbitals with equal energies undergo hybridization. • The number of hybrid orbitals formed is equal to the number of atomic orbitals mixing. • It is not necessary that all the half-filled orbitals must participate in hybridization. Even completely filled orbitals with slightly different energies can also participate. • Hybridization happens only during the bond formation and not in an isolated gaseous atom. • The shape of the molecule can be predicted if hybridization of the molecule is known.