Physical & Chemical Properties of Alcohols PDF

Alcohols  Physical Properties 1. One of the most important physical properties of alcohols is that they form hydrogen bonds. The oxygen, in the functional group (OH), has greater electronegativity than carbon and hydrogen. So the C-O and O-H bonds are polar & create the hydrogen bond....

Alcohols  Physical Properties 1. One of the most important physical properties of alcohols is that they form hydrogen bonds. The oxygen, in the functional group (OH), has greater electronegativity than carbon and hydrogen. So the C-O and O-H bonds are polar & create the hydrogen bond. Thus alcohol molecules are capable of forming hydrogen bonds with each other.  Physical Properties Boiling Points °C 2. Boiling points :. a) Increase because of the hydrogen bonds. b) Increase also with the number of carbon atoms. c) Increase if more than one hydroxyl group. d) Decrease with branching Penthane between isomers. Physical Properties Density Solubility in water Kg/L g/100mL 3. The Density of alcohols increases with the molecular weight of the alcohol. Physical Properties 4. Soluble in water: The hydrogen bonds also cause them to be able to dissolve in water. Uses of Alcohols Methanol.  It is used as a solvent.  It is used as a raw material for the production of formaldehyde. Ethanol.  It is the main component of alcoholic Ethanol beverages.  Also used as antifreeze since its freezing point is -114°.  Used in perfumes, lubricants and sweeteners.  Uses of Alcohols Ethanol (cont.) Is also used as fuel by mixing it with gasoline to produce gasohol. The world's top ethanol fuel producers in 2011 were the United States and Brazil, accounting together for 87.1% of world production. Uses of Ethanol  Uses of Alcohols Glycerin or glycerol or Propane-1,2,3-triol. Due to its moisturizing capacity it is used: a) In cosmetic creams b) In liquid medicines c) In suppositories Uses of Alcohols Glycol is 1,2 ethane diol. It is used as antifreeze in car radiators, because it has an extremely low freezing temperature. It is also used to make Coolant that is a mixture of antifreeze and water at a 50:50 ratio Uses of Alcohols Isopropyl alcohol. Because it is antiseptic, it is used as rubbing alcohol. Uses of Alcohols Cetyl Alcohol (has 16 C) It is a solid substance, used in the manufacture of cosmetics and creams. It lubricates & softens the skin. Sources of Alcohols  Obtaining Alcohols 1. Industrially: Fermentation of carbohydrates. From sugar cane, barley or corn that are fermented with yeast to produce ethanol. Yeast 3 Glucose Ethanol Whiskey is made from fermented grains (most often Beer is produced by the rye, wheat, corn, or barley. fermentation malted barley. Obtaining Alcohols 2. In the Laboratory: Addition of water to an alkene. The alkene with water, in an acid medium as a catalyst, produces alcohol. H2SO4 Chemical Properties 1. Dehydration of an alcohol 2. Alcohols reacting as an acid 3. Alcohols reacting as a base 4. Oxidation of different types of alcohols 5. Combustion Chemical Properties Dehydration of an alcohol Chemical Properties of Alcohols Alcohols are amphoteric. An amphoteric substance is a substance that can react as either an acid or a base. Chemical Properties of Alcohols Alcohols as acids. Against metallic sodium, the alcohol reacts as an acid to form an alkoxide. Sodium Methoxide This white solid, obtained from methanol, is a widely used reagent in industry and the laboratory. Chemical Properties of Alcohols An Alkoxide is an organic functional group formed when a hydrogen atom is removed from the -OH group and is substituted by a metal. Alkoxides are strong bases. The general formula of alkoxides is: Chemical Properties of Alcohols Alcohols as a base. Against a hydracid (HX) they react as bases to form an alkyl halide. Chloroethane Alkyl halides are an organic function where hydrocarbons contain halogen atoms in their molecule. Their general formula is RX. The X represents the halogen. Chemical Properties of Alcohols Oxidation of alcohols The most commonly used oxidizing agents are: Potassium permanganate Chromic acid Potassium dichromate Either one can be represented with the symbol below: Chemical Properties of Alcohols: Oxidation of alcohols Primary alcohols are first oxidized to aldehydes. If the oxidation does not stop, it continues until a carboxylic acid is formed. Chemical Properties of Alcohols Secondary alcohols are oxidized to ketones. Secondary alcohol Ketone Chemical Properties of Alcohols Tertiary alcohols are resistant to oxidation. Are NOT oxidized! Chemical Properties of Alcohols Combustion The combustion of methanol is an exothermic reaction because heat is released.