ORG CHEM LAB

• Covalent bonding


  Occurs between two non-metallic atoms, characterized by the sharing of electron pairs between the atoms
• Berzelius proposed that compounds derived from living things were organic and that all others were inorganic


  1807
• Common elements in organic compounds

  • Carbon
  • Hydrogen
  • Oxygen
  • Nitrogen
  • Sulfur
  • Phosphorous
• Recrystallization


  Usually employed for purification of crystalline substances. The percentage yield of the recrystallized substance can be calculated
• Results: yellow precipitate - Test for Phosphorous
• Ionic bonding


  Complete transfer of valence electron(s) between atoms, generating two oppositely charged ions. In ionic bonds, the metal loses electrons to become a positively charged cation, whereas the nonmetal accepts those electrons to become a negatively charged anion
• Vital Force Theory - living things possessed a vital force as a result of their origin
• Results: white precipitate - Test for Sulfur
• Organic chemistry


  Study of carbon and its derivatives
• Chromatography


  Good for separating mixtures of dissolved substances with different colors. Paper chromatography is a technique for separating dissolved chemical substances by taking advantage of their different rates of migration across sheets of paper
• Separation by solubility differences

  One component of a mixture may be readily soluble in a given solvent, whereas the other component may be insoluble. The mixture is shaken with the solvent and filtered
• Paper chromatography


  Technique for separating dissolved chemical substances by taking advantage of their different rates of migration across sheets of paper
• Liquid-liquid extraction


  Involves the exchange of compounds between two solvents that are immiscible or only partially miscible
• All hydrocarbons can be halogenated under certain conditions
• Distillation

  Simple distillation is good for separating a volatile liquid from non-volatile substances in a solution
• Baeyer’s test for unsaturated hydrocarbons results in a dark brown precipitate for a positive result
• Complete combustion produces carbon dioxide and water with energy, incomplete combustion produces carbon and carbon monoxide
• Hydrocarbons, in general, are volatile. The rate of evaporation is related to the molar mass of the substance
• Chromatography


  • Good for separating mixtures of dissolved substances that have different colors, such as inks and plant dyes
• Chromatography

  Based on the principle where molecules in a mixture applied onto the surface or into the solid, and stationary phase is separating from each other while moving with the aid of a mobile phase
• Positive result of reaction with KMnO4 is a purple color change to brown, negative result is no reaction
• Bromine test for unsaturated hydrocarbons results in a color change from yellow to clear solution for a positive result
• Fermentation


  Chemical process by which molecules such as glucose (sugar) are broken down anaerobically
• Fermentation is a metabolic process that releases energy from sugar or other organic substrates through various enzyme actions
• Louis Pasteur


  Described the change brought by yeast and other microorganisms in the absence of air, recognized that ethyl alcohol and carbon dioxide are produced during fermentation together with other byproducts
• Industrial ethyl alcohol produced from fermentation is a source of biofuel
• Different types of fermented products


  • Wine
  • Beer
  • Biofuels
  • Yoghurt
  • Pickles
  • Bread
  • Sour foods containing lactic acid
  • Some antibiotics and vitamins
• Pros of eating fermented foods


  • Improves digestion and helps to maintain intestinal bacteria
  • Has anti-cancer effect
  • Improves immune system
  • Reduces lactose intolerance
• Tollens' test procedure


  1. Put 1 mL of silver nitrate in test tube

  2. Add 1 drop of sodium hydroxide solution

  3. Shake the test tube

  4. Observe dark brown precipitate

  5. Add ammonium hydroxide dropwise until solution becomes colourless

  6. Add 2-3 drops of the sample

  7. Put the test tube in the water bath for 5 minutes

  8. Observe formation of silver mirror

  9. Add dilute nitric acid and drain off the solution
• Tollens' test


  Qualitative laboratory test used to distinguish between an aldehyde and a ketone
• Tollens' reagent


  Colorless, basic, aqueous solution containing silver ions coordinated to ammonia [Ag(NH3)2+]
• Preparation of Tollens' reagent


  1. Aqueous silver nitrate is mixed with aqueous sodium hydroxide

  2. Aqueous ammonia is added drop-wise until the precipitated silver oxide completely dissolves
• Benedict's test


  Chemical test that can be used to check for the presence of reducing sugars in a given analyte
• Benedict's reagent


  Complex mixture of sodium citrate, sodium carbonate, and the pentahydrate of copper (II) sulfate
• When exposed to reducing sugars, the reactions undergone by Benedict's reagent result in the formation of a brick-red precipitate, which indicates a positive Benedict's test
• Saponification


  Hydrolysis of fats and oils by a strong base such as NaOH and KOH, forming glycerol and salts of fatty acids
• Soaps


  Metallic salts of fatty acids
• Saponification of low molecular weight esters produces salts which do not possess the properties of soap
• Detergents


  Substances constituting a mixture of the sodium salts of the sulphuric acid esters of lauryl and acetyl alcohols
• Detergent action of soaps


  Attributed to the presence of a polar end (water soluble) and a non-polar end which is oil soluble