Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chapter 12 Organic Compounds with Oxygen and Sulfur 12.2 Properties of Alcohols, Ethers, and Thiols Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 1 Boiling Points of Alcohols Alcohols • contain polar OH groups. • form hydrogen bonds with other alcohol molecules. • have higher boiling points than alkanes and ethers of similar mass. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 2 Boiling Points of Ethers Ethers • do not have a polar group. • have an O atom, but there is no H attached. • cannot form hydrogen bonds between ether molecules. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings 3 Solubility of Alcohols and Ethers in Water Alcohols and ethers • are more soluble in water than alkanes because the oxygen atom can hydrogen bond with water. • with 1-4 C atoms are soluble, but not with 5 or more C atoms. 4 Comparing Solubility and Boiling Points Compound Alkane CH3─CH2─CH3 Ether CH3─O─CH3 Alcohol CH3─CH2─OH Molar Mass Boiling Point (°C) Soluble in Water? 44 -42 No 46 -23 Yes 46 78 Yes 5 Reactivity of Alkanes vs. Alcohols Hydrocarbon + O2 carbon dioxide + water + heat energy D Ex. CH4 + 2O2 CO2 + 2H2O D Heat released is 802 kJ/mol of methane Effect of partially oxidizing a hydrocarbon, let’s look at the combustion reaction of CH3OH (methanol), in which 1 H has been replaced by an –OH group. 2CH3OH + 3O2 2CO2 + 4H2O D Heat released is 640 kJ/mol of methanol (1.5 moles of O2 required to with 1 mole of CH3OH!) 6 These reactions illustrates two important principles. 1st, the more reduced a molecule, the more energy is released during oxidation on a molar basis. Methane is fully reduced and gives off more energy during combustion than methanol. 2nd, the number of oxygen molecules required to react with a fuel molecule can give an estimate of how much energy is available. More highly reduced molecules require more oxygen during combustion and produces more energy. 7 Reduction of hydrocarbons vs. their oxidation OH CH3OH Partially Oxidized 8 Solubility of Phenol Phenol • is soluble in water. • has a hydroxyl group that ionizes slightly (weak acid). • is corrosive and irritating to skin. OH O- + H2O + H3O+ 9