Organic Chemistry Chapter 1: Alkanes and Chemical Bonds

Chemical Bonds

• Ionic bonds result from the transfer of electrons
• Covalent bonds result from the sharing of electrons
• Covalent bonds are typical of carbon compounds and are of chief importance in organic chemistry

Hybrid Orbitals

• Hybrid orbitals are formed by mixing (hybridizing) carbon's atomic orbitals
• When carbon bonds to 4 other atoms, the 2s orbital and all three 2p orbitals in the valence shell combine to produce four sp3 hybrid orbitals
• Hybrid orbitals are used to describe the bonds between carbon atoms

sp Hybridization

• Carbon has sp hybridization when bound to two other atoms with the help of two double bonds or one single and one triple bond
• sp hybridization results in a linear arrangement of atoms with a bond angle of 180°

sp2 Hybridization

• Carbon is sp2 hybridized when bonding takes place between 1 s-orbital with two p orbitals
• sp2 hybridization results in a triangular arrangement of atoms with 120° angles between bonds

sp3 Hybridization

• Carbon has sp3 hybridization when bonded to four other atoms
• sp3 hybridization results in a tetrahedral arrangement of atoms with a bond angle of 109.5°
• Example: Hybridization of CH4 (Methane)

Properties of Alkanes

• Alkanes are nonpolar, making them insoluble in water but soluble in nonpolar solvents
• Alkanes have densities from 0.62 g/mL to about 0.79 g/mL, which is less than the density of water (1.0 g/mL)
• Alkanes with 1-4 carbon atoms are gases at room temperature and are widely used as heating fuels
• Alkanes with 5-9 carbon atoms are liquids at room temperature and are used in fuels such as gasoline
• Alkanes with 9-17 carbon atoms have higher boiling points and are found in kerosene, diesel, and jet fuels
• Alkanes with 18 and more carbon atoms are waxy solids at room temperature and are used in waxy coatings
• Alkanes with 25 and more carbon atoms are semi-solid mixtures of hydrocarbons used in ointments, cosmetics, and as a lubricant (e.g. Vaseline)