Alkanes and Aromatic Hydrocarbons Organic Compounds Bonding in Hydrocarbons Naming Alkanes Properties of Alkanes Timberlake LecturePLUS

Timberlake LecturePLUS “The most important hypothesis in all of biology…is that everything that animals do, atoms do. In other words, there is nothing that living things do that cannot be understood from the point of view that they are made of atoms acting according to the laws of physics.” Richard Feynman (1918-1988) Timberlake LecturePLUS

Timberlake LecturePLUS Organic Compounds Contain carbon Have covalent bonds Have low melting points Have low boiling points Burn in air (oxygen) Are soluble in nonpolar solvents Form large molecules Timberlake LecturePLUS

Timberlake LecturePLUS Alkanes Contain C and H only Contain single bonds C-C Have 4 bonds to every carbon (C) atom Are nonpolar Timberlake LecturePLUS

Complete Structural Formulas Show the bonds between each of the atoms H H   H  C  H H C H CH4 , methane In methane, CH4 the four valence electrons of carbon are shared with the single electrons of four hydrogen (H) atoms. Each pair of electrons is a single bond, which can be drawn as a line. When a structure is drawn to show each bond, it is called a complete structural formula. Timberlake LecturePLUS

Timberlake LecturePLUS More Alkanes H H Condensed Structural Formulas H C C H CH3 CH3 H H Ethane H H H H C C C H CH3 CH2 CH3 H H H Propane The complete structural formula for ethane shows the single bonds between two carbon atoms and six H atoms. The complete structural formula of propane shows the 3-carbon chain with single bonds to the attached H atoms. To write a condensed structural formula, the H atoms are written as a group next to their respective C atoms. Timberlake LecturePLUS

Timberlake LecturePLUS IUPAC Names Name # carbons Structural Formula Methane 1 CH4 Ethane 2 CH3CH3 Propane 3 CH3CH2CH3 Butane 4 CH3CH2CH2CH3 Pentane 5 CH3CH2CH2CH2CH3 The names of organic compounds are determined by the IUPAC rules (International Union of Pure and Applied Chemistry). The stem of the name states the number of carbon atoms in the carbon chain of the compounds. The suffix, in this case –ane, indicates the alkane family. Timberlake LecturePLUS

Timberlake LecturePLUS IUPAC NAMES Name # carbons Structural Formula Hexane 6 CH3CH2CH2CH2CH2CH3 Heptane 7 CH3CH2CH2CH2CH2CH2CH3 Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3 Nonane 9 CH3 CH2 CH2CH2CH2CH2CH2CH2CH3 Decane 10 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3 Timberlake LecturePLUS

Timberlake LecturePLUS Learning Check Alk1 A. What is the condensed formula for H H H H H C C C C H B. What is its molecular formula? C. What is its name? Timberlake LecturePLUS

Timberlake LecturePLUS Solution Alk1 A. CH3CH2CH2CH3 B. C4H10 C. butane Timberlake LecturePLUS

Timberlake LecturePLUS Reactions of Alkanes Combustion alkane + O2 CO2 + H2O + heat Timberlake LecturePLUS

Timberlake LecturePLUS Combustion In the Cell Metabolic oxidation is combustion C6H12 O6 + 6O2 6CO2 + 6H2O + heat glucose Timberlake LecturePLUS

Timberlake LecturePLUS Learning Check Alk2 Complete the combustion reaction for C3H8 + O2 + Balance your equation Timberlake LecturePLUS

Timberlake LecturePLUS Solution Alk2 Step 1 C3H8 + O2 CO2 + H2O Step 2 C3H8 + O2 3 CO2 + 4 H2O Step 3 C3H8 + 5 O2 3 CO2 + 4 H2O To balance the atoms in the formula C3H8, we place a coefficient of 3 in front of CO2 and a coefficient of 4 in front of H2O. The total O in the products is 10 O (6 O in 3CO2 and 4 O in 4 H2O). To balance the 10 O, a coefficient of 5 is placed in front of the O2. Timberlake LecturePLUS

Timberlake LecturePLUS Learning Check Alk3 Complete and balance the reaction for the complete combustion of C7H16 Timberlake LecturePLUS

Timberlake LecturePLUS Solution Alk3 Step 1 C7H16 + O2 CO2 + H2O Step 2 C7H16 + O2 7 CO2 + 8 H2O Step 3 C7H16 + 11 O2 7 CO2 + 8 H2O The carbon has a subscript 7, which means we need to place a coefficient of 7 in front of CO2. The H subscript 16 is balanced by placing a coefficient of 8 in front of H2O. Finally, the total O of 22 ( 14 + 8) indicates that a coefficient of 11 in front of O2 will balance the O atoms. Timberlake LecturePLUS