ALCOHOLS NOMENCLATURE

• Alcohols


  Characterized by one or more hydroxyl groups attached to a carbon atom of a hydrocarbon chain

  
• IUPAC nomenclature for alcohols

  The hydroxyl group is indicated by the ending —ol

  
• Common name for alcohols

  The separated word "alcohol" is placed after the name of the alkyl group
• Naming alcohols


  1. Name the longest chain to which the hydroxyl group is attached

  2. Drop the —e, then add —ol

  3. Number the longest chain to give the lower number to the carbon with the attached hydroxyl group

  4. Locate the position of the hydroxyl group

  5. Locate and name any branches attached to the chain

  
• Number of atoms and corresponding root word

  • 1 - METH-
  • 2 - ETH-
  • 3 - PROP-
  • 4 - BUT-
  • 5 - PENT-
  • 6 - HEX
  • 7 - HEPT-
  • 8 - OCT-
  • 9 - NON-
  • 10 - DEC-
• Classification of alcohols


  • Depending on whether one, two, or three organic groups are connected to the hydroxyl-bearing carbon atom
  • According to number of hydroxyl groups attached to their molecules
  • Allylic carbon atom (has an adjacent allyl)
  • Benzylic carbon atom (has benzene ring and carbon + OH attached to the ring)

  
• Physicochemical properties of alcohols

  • Most of the common alcohols are colorless liquids at room temperature
  • Higher alcohols: those containing 4-10 atoms, are somewhat viscous or oily, they have heavy fruity odors
  • Some of the highly branched alcohols containing more than 12 carbon atoms are solids at room temperature
  • The boiling points of alcohols are much higher than those of alkanes with similar molecular weights
  • The hydroxyl group is referred to as hydrophilic (water-loving) group, because it forms hydrogen bonds with water and enhances the solubility of an alcohol in water
  • Methanol, ethanol, n-propyl alcohol, isopropyl alcohol are all miscible with water
  • Alcohols with higher molecular weights tend to be less water-soluble, because the hydrocarbon part of the molecules, which is hydrophobic (water-hating), is larger with increased molecular weight
• Lower alcohols (up to 4 carbon atoms)

  • Methanol
  • Ethanol
  • Isopropyl alcohol
  • Ethylene glycol
  • Glycerol
• Methanol


  • Simplest alcohol (1 carbon containing)
  • Methanol was at one time produced from wood distillation and is still sometimes called wood alcohol
  • At present, methanol is manufactured from carbon monoxide and hydrogen
  • Most of it is used to produce formaldehyde and other chemicals, but some is used as a solvent and as an antifreeze
  • Methanol is highly toxic and can cause permanent blindness because when taken internally, it is oxidized to formaldehyde, which binds to opsin, preventing formation of rhodopsin, the light sensitive pigment needed for vision
  • Formaldehyde is also carcinogenic
• Ethanol


  • AKA grain alcohol
  • Ethyl alcohol has been produced mostly through the fermentation of fruit juices, the fermented juice could be stored in a sealed container, and this primitive wine remained safe drink throughout the winter
  • Many different sources can provide the sugars and starches that are broken down to simpler compounds during fermentation
  • Besides fermentation, ethanol is also manufactured by the acid-catalyzed hydration of ethylene
  • Since earlier times, ethanol has been known as an ingredient in fermented beverages (beer, wine, and whiskey)
  • The term proof, as used in the United States in reference to alcoholic beverages, is approximately twice the volume percentage of alcohol present
  • Ethanol is used as a solvent, as a topical antiseptic (for example, when drawing blood)
  • It also can be used as a fuel, often as a blend with gasoline
• Isopropyl alcohol


  • 2-Propanol (isopropyl alcohol) is manufactured commercially by the acid-catalyzed hydration of propene
  • AKA rubbing alcohol
  • It is the main component of rubbing alcohol and is used in many household and personal care products
• Ethylene glycol


  • The name ethylene glycol refers literally to "the glycol made from ethylene"
  • Ethylene glycol is commonly used as automotive antifreeze (found in air-conditioning units) and as an ingredient in hydraulic fluids, printing inks, and paint solvents
  • PEG: polyethylene glycol (another variety of ethylene glycol)

  
• Glycerol

  • Glycerol is a sweet syrupy substance with three alcohol hydroxyl groups
  • Glycerol was first obtained as a by-product of soap manufacture
  • Propan-1,2,3-triol

  
• Chemical reactions of alcohols

  1. Oxidation

  2. Dehydration

  3. Substitution

  4. Esterification

  
• Oxidation of alcohols

  • Alcohols may be oxidized to give ketones, aldehydes, and carboxylic acids
  • These functional groups are useful for further reactions; for example, ketones and aldehydes can be used in subsequent Grignard reactions, and carboxylic acids can be used for esterification
  • Whether alcohol is primary, secondary, or tertiary will determine if they will yield ketones and aldehydes
  • Primary: aldehyde —> carboxylic acid (if further oxidized)
  • Secondary: ketone
  • Tertiary: usually no further oxidation, and usually don't oxidize without breaking carbon-carbon bonds
  • At higher temperatures, a more concentrated acid like chromic acid can break carbon-carbon bonds, however, such strong oxidations are usually pulled
  • Addition of oxygen and loss of hydrogen
  • PCC: pyridinium chlorochromate (CrO3, pyridine with HCl)

  
• Dehydration of alcohols


  • Conversion of an alcohol to an alkene requires removal of the hydroxyl group and a hydrogen atom on the adjacent carbon atom
  • Removal of water
  • Dehydration reactions are most commonly carried out by warming the alcohol in the presence of a strong dehydrating acid (such as a concentrated sulfuric acid)
  • Yields alkenes
  • Dehydration of Alcohols to ethers: Simple alcohols can undergo intermolecular dehydration to give ethers, only effective with methanol and other simple primary alcohols, most economical method for making ethyl ether

  
• Substitution of alcohols

  • Alkyl halides are often synthesized from alcohol, in effect substituting a halogen atom for the hydroxyl group
  • Give their best yields with tertiary alcohols
  • HCl, HBr, and HI acids are useful for substitution reactions
  • Thionyl Chloride: useful in making alkyl chlorides
  • Phosphorus tribromide; in alkyl bromides
  • Phosphorus Triiodide: in alkyl iodides

  
• Esterification of alcohols


  • Alcohols can combine with acids to form carboxylic esters
  • Called as Fischer Esterification

  
• Phenols

  • Any of a family of organic compounds characterized by a hydroxyl group attached to a carbon atom that is a part of an aromatic ring
  • Simplest member, monohydroxybenzene
  • Also known as benzenol or carbolic acid

  
• Physical properties of phenols

  • Monohydroxy compounds are only slightly soluble in water but are miscible with organic solvents
  • Water solubility increases and solubility in organic solvents decreases with the introduction of additional hydroxyl groups
  • Simple monohydric phenols are either corrosive liquids or low melting solids
  • The dihydric and trihydric phenols are solids
  • Similar to alcohol, they form stronger hydrogen bonds, more soluble in water and higher MP than alcohols
  • In 1865 the British surgeon Joseph Lister used phenol as an antiseptic to sterilize his operating field, with phenol used in this manner, the mortality rate from surgical amputations fell from 45 to 15% in Lister's ward
  • Phenol is quite toxic, however, and concentrated solutions cause severe but painless burns of the skin and mucous membranes
  • Less toxic phenol, such as n-hexylresorcinol, have supplanter phenol itself in cough drops and other antiseptic applications
  • Butylated hydroxytoluene (BHT) has a much lower toxicity and is a common antioxidant in foods