organic

• Alcohols


  Organic derivatives of water
• Phenols


  Alcohols with the hydroxyl group (-OH) bonded to an aromatic ring

  
• Structure of Alcohols


  • General formula: R-OH
  • Functional group: -OH (hydroxyl group)
  • alcohol: R = alkyl
  • phenol: Ar = aromatic ring

  
• IUPAC Nomenclature/Names


  1. Select the longest carbon chain containing the OH group. Change e (alkane) to ol

  2. Number the carbon chain to give the OH group the lowest number, and apply all other rules of nomenclature

  3. If a molecule contains both an -OH group and a C=C or CC bond, the -OH group takes preferences before the C=C or CC in getting the lower number

  
• Unsaturated Alcohols


  Priority goes to the hydroxyl group; assign that carbon the lowest number<|>Use alkene or alkyne name

  
• Unsaturated Alcohols


  • 4-penten-2-ol (pent-4-en-2-ol)
• Hydroxy Substituent


  When -OH is part of a higher priority class of compound, it is named as hydroxy

  
• Hydroxy Substituent


  • 4-hydroxybutanoic acid
• Naming Diols


  Two numbers are needed to locate the two -OH groups<|>Use -diol as suffix instead of -ol
• Glycols


  1, 2 diols (vicinal diols) are called glycols<|>Common names for glycols use the name of the alkene from which they were made

  
• Naming Phenols


  • OH group is assumed to be on carbon 1<|>For common names of disubstituted phenols, use ortho- for 1,2; meta- for 1,3; and para- for 1,4

  
• Physical Properties

  • Unusually high boiling points due to hydrogen bonding between molecules
  • Small alcohols are miscible in water, but solubility decreases as the size of the alkyl group increases

  
• Boiling Points

  Intermolecular forces involved: hydrogen bonding, dipole-dipole attractions<|>In increasing order: Propane < dimethyl ether < ethanol

  
• Boiling points reflect the strength of forces between molecules. The more they stick together, the more energy it will take to blast them into the atmosphere as gases.
• There are 3 important trends to consider: 1) The relative strength of the four intermolecular forces, 2) Boiling points increase as the number of carbons is increased, 3) Branching decreases boiling point.

  
• Solubility in Water

  Solubility decreases as the size of the alkyl group increases
• The longer the carbon chain, the higher the boiling point due to the increased Van der Waals attractive forces between molecules, and the lower the water solubility because the non-polar part is getting longer and hence a smaller proportion of the molecule is interacting in the water.

  
• The more spherical (branched) the molecules, the less surface area it has, resulting in a lower boiling point than other isomeric alcohols due to less Van der Waals attractive forces between molecules, and more soluble in water because the non-polar surface area is minimized.

  
• The extent of solubility of any alcohol in water depends on the capability of its molecule to form hydrogen bonds with water. But, within isomeric alcohols, solubility increases with branching due to the decrease in surface area of the non-polar hydrocarbon part.

  
• Acidity of Alcohols & Phenols

  pKa range: 15.5-18.0 (pKa water = 15.7)<|>Acidity decreases as alkyl group increases<|>Halogens increase the acidity (inductive effect)<|>Phenol (10.0) is 100 million times more acidic than cyclohexanol (18.0) (delocalization)

  
• Formation of Phenoxide Ion


  Phenols (pKa ~10) are much more acidic than alcohols (pKa ~ 16) due to resonance stabilization of the phenoxide ion<|>Phenols react with NaOH solutions (but alcohols do not), forming salts that are soluble in dilute aqueous solution

  
• Effect of electron-withdrawing groups on Acidity of Phenols

  Acidity increase; -ve charge is delocalize to the groups
• Effect of electron-donating groups on Acidity of Phenols

  Acidity decrease; -ve charge is localize to oxygen atom (ROH)
• Synthesis of Alcohols

  1. Alcohols from Alkene: a) Hydration, b) Oxymercuration-Demercuration, c) Hydroboration-Oxidation

  
• Hydration of Alkenes

  Water in Acid Solution, H2O/H+
• Oxymercuration - Demercuration

  1. Reagent is mercury(II) acetate which dissociates slightly to form +Hg(OAc) in H2O

  2. +Hg(OAc) is the electrophile, will be attacked by the pi bond

  3. Sodium borohydride (NaBH4), a reducing agent, replaces the mercury with hydrogen
• Electron-donating substituents


  Make the phenol less acidic by destabilizing the anion
• Electron-withdrawing substituents

  Make the phenol more acidic by stabilizing the phenoxide anion
• Hydration


  Markonikov product formed, water in acid solution (H2O, H+)
• Oxymercuration-Demercuration


  Markovnikov product formed, Anti addition of H-OH, No rearrangements
• Hydroboration-Oxidation


  Anti-Markovnikov product formed, Syn addition of H-OH
• Oxymercuration - demercuration


  Reagent is mercury(II) acetate which dissociates slightly to form +Hg(OAc) in H2O, +Hg(OAc) is the electrophile, will be attacked by the pi bond, Sodium borohydride (NaBH4), a reducing agent, replaces the mercury with hydrogen
• Hydroboration - Oxidation


  Borane, BH3, adds a hydrogen to the most substituted carbon in the double bond, The alkylborane is then oxidized to the alcohol which is the anti-Mark product

  
• Reduction of aldehyde


  Yields 1º alcohol
• Reduction of ketone

  Yields 2º alcohol
• Reducing agents

  • Sodium borohydride, NaBH4
  • Lithium aluminum hydride, LiAlH4
  • H2/ Raney nickel (Catalytic Hydrogenation)
• Sodium Borohydride (NaBH4)

  Hydride ion, H-, attacks the carbonyl carbon, forming an alkoxide ion, Then the alkoxide ion is protonated by dilute acid, Only reacts with carbonyl of aldehyde or ketone, not with carbonyls of esters or carboxylic acids

  
• Lithium Aluminum Hydride (LiAlH4)


  Stronger reducing agent than sodium borohydride, but dangerous to work with, Converts esters and acids to 1º alcohols
• Catalytic Hydrogenation

  Add H2 with Raney nickel catalyst, Also reduces any C=C bonds
• Grignard Reagents


  Formula R-Mg-X (reacts like R:- +MgX), Stabilized by anhydrous ether, Iodides most reactive, May be formed from any halide