UNIT 4: Alcohols, Phenols and Ethers

12.1 Alcohols: Structure & Physical Properties Alcohol- organic compound that contains a hydroxyl group (-OH) attached to an alkyl group. Has similar bond angle to water. -OH groups are very polar because the O and H have different electronegativities. H bonds hold alcohol molecules together. Very high boiling points because of the H bonds. The smaller the molecule, the more soluble in water (much more insoluble past 6 carbons) Solubility has to do with the alcohol being able to form the intermolecular H bonds with water molecules. As the nonpolar portion of the alcohol grows (carbon chain), solubility decreases. Think hydrophobic/hydrophilic (from biology)

12.2 Alcohols: Nomenclature Using the IUPAC system 1. Determine the name of the parent compound (the longest carbon chain with the –OH group) 2. Replace the –e ending of the alkane parent name with –ol ending for alcohol. Ex. Ethane becomes ethanol, Propane becomes propanol 3. Number the parent chain to give the carbon with the hydroxyl group the lowest number. Name & number all substituents & add them as prefixes to the alcohol parent name.

Nomenclature Continued 5. Alcohols with 2 hydroxyl groups are named –diols (-triols). A number giving the position of each of the hydroxyl groups is needed in these cases. 1, 2- propanediol Using Common Names Common names come from the alkyl group corresponding to the parent compound. Name the alkyl group followed by “alcohol.” Some alcohols come from historical names

Nomenclature Continued IUPAC- 1,2,3-propanetriol Common- glycerol

12.3 Medically Important Alcohols 1. Methanol (Methyl alcohol) - colorless, odorless, liquid, toxic - used as a solvent for other organic compounds -used to make methanal (formaldehyde) -can be made by heating wood in the absence of air -can be used as fuel

Medically Important Alcohols 2. Ethanol (Ethyl alcohol) -colorless, odorless, liquid -drinkable alcohol OR can be used as a solvent for other organic compounds -comes from fermentation of carbohydrates (sugars/ starches) -type of beverage depends on the starting material (scotch- grain, bourbon-corn, red wine- red/purple grapes) C6H12O6 → 2CH3CH2OH + 2CO2 Glucose enzyme Ethanol (sugar) action

Medically Important Alcohols Beverages can have diff. concentrations. Beverages with high concentrations must be distilled. Pure ethanol (100%) is for lab use only and is denatured (not drinkable). Does not change chemical composition, mixed with other chemicals to make toxic.

Medically Important Alcohols 3. 2-Propanol (isopropyl alcohol) -called “rubbing alcohol” because it was once used to give patients baths who had high fevers -used as disinfectant and astringent -colorless, slight odor, toxic 4. 1, 2-Ethanediol (ethylene glycol) -antifreeze -when added to water, decreases freezing point and increases boiling point -sweet taste, poisonous -colorless, so dye is added

Medically Important Alcohols 5. 1,2,3-propantriol (glycerol) -viscous (thick, less fluid), sweet, non-toxic, liquid -soluble in water -used in make-up, lubricants and pharmaceuticals -comes from the hydrolysis of fats (the addition of water causes the formation of soap)

12.4 Classification of Alcohols Based on the number of alkyl groups attached to the carbinol carbon (the carbon bonded to the –OH group) Primary (1°)- single alkyl group Secondary (2°)- 2 alkyl groups Tertiary (3°)- 3 alkyl groups No alkyl groups- Methyl alcohol

12.5 Reactions Involving Alcohols Preparation of Alcohols Alcohol is created by adding a water molecule to the carbon- carbon double bond of an alkene (addition reaction) -called hydration -requires small amount of acid as a catalyst -can also be created through the hydrogenation of an aldehyde of ketone (adding H, therefore reducing the aldehyde or ketone) -catalyst also needed

Preparation of Alcohols Other examples: Reduction of an aldehyde by adding H2 Propanal Hydrogen Propanol Reduction of a ketone by adding H2 + H2 → Propanone Hydrogen 2-Propanol

Reactions Involving Alcohols Dehydration of Alcohols -loss of water when heated with acid (sulfuric acid or phosphoric acid) -elimination reaction because losing atoms or ions from structure (-OH and –H) -water and alkene produced -reverse of hydration

Dehydration of Alcohols Sometimes you can produce multiple products. Recall major and minor products. The major product in an elimination reaction is the alkene with the greatest number of alkyl groups on the double bonded carbon. (Zaitsev’s Rule)

Oxidation Reactions Oxidation Reactions -gain of oxygen or loss of hydrogen -need oxidizing agent to complete reaction (potassium permanganate or chromic acid) -in book, the symbol [O] is used over the arrow to show that an oxidizing agent is being used -creates an aldehyde or ketone

Oxidation Reactions

Oxidation Reactions Oxidation of methanol or a 1° alcohol produces an aldehyde, 2° produces ketone, 3° cannot be oxidized Side note on oxidation- Ethanol is oxidized in the liver to become ethanol (acetaldehyde). If too much ethanol in the blood, then too much ethanol will be formed. This causes the effects of the “hangover.” Continued oxidation makes ethanoic acid (acetic acid) which is used as energy in the body. It is then oxidized to carbon dioxide and water.

12.6 Oxidation and Reduction in Living Systems LEO the lion says GER Lose electrons- oxidation Gain electrons- reduction   This occurs in inorganic compounds (Recall from Chemistry) Ex. Ag° → Ag+ + 1e- oxidation Br + 1e- → Br- reduction

Oxidation and Reduction With organic compounds it is hard to tell whether Oxidation or Reduction has occurred because there may not be a change in charge.   Oxidation = gain of O or loss of H Reduction = loss of O or gain of H oxidize alkane + oxygen  alcohol – hydrogen  aldehyde + oxygen  carboxylic acid   reduce

12.7 Phenols Compounds in which a hydroxyl group is attached to a benzene ring. -polar like alcohols because of the –OH -simpler phenols are somewhat soluble in water -found in flavorings, used as preservatives, used in germicides -dilute solutions of phenol used as antiseptics and disinfectants -concentrated phenols can cause severe burns

12.8 Ethers -2 alkyl groups bonded to an oxygen (center) -polar -no –OH group so they do not bond together using H bonds -lower boiling points than alcohol of a similar molar mass, but higher boiling points than that of alkanes of similar molar mass.

Nomenclature of Ethers IUPAC -Name is based on alkoxy group (alkyl group bonded to oxygen atom)- substituent Ex. CH3 - O methoxy CH3CH2 - O ethoxy Ex. IUPAC- Ethoxyethane Common- Diethyl ether Common System Name both alkyl groups as prefixes in front of the ether Can name alphabetically or by size

Ether Properties -Chemically inert -do not react under normal conditions -extremely volatile, highly flammable Prepared in synthesis of 2 alcohols which removes water (dehydration) H+ + → + H2O Heat Methanol Methanol Dimethyl ether Diethyl ether first general anesthetic