PRPM112 LAB: EX 11

• CARBOXYLIC ACIDS


  organic compounds containing a carboxyl (R-COOH) functional group
• CARBOXYLIC ACIDS


  occur widely in nature, often combined with other functional groups, just like in fats, oils, and waxes
• CARBOXYLIC ACIDS

  contains an acyl group (RCO–) with a hydroxyl group attached to it
• CARBOXYLIC ACIDS

  nucleophilic substitution reaction, that is, replacing the hydroxyl group with substituents such as halo, alkoxyl, amino, and acyloxy
• SYNTHESIS OF CARBOXYLIC ACIDS

  • oxidation of primary alcohols (using potassium dichromate or potassium permanganate)
  • chemical process also occurs biologically in the liver on ethanol metabolism
• METABOLISM (OXIDATION OF ETHANOL)

  • ethanol is metabolized into acetaldehyde through an enzyme known as alcohol dehydrogenase (this process can also occur through CYP450 enzyme)
  • acetaldehyde is further metabolized into acetic acid through an enzyme known as aldehyde dehydrogenase
  • acetate metabolite is a more excretable form
  • prevents the accumulation of the toxic acetaldehyde metabolite
• TEST FOR CARBOXYLIC ACIDS

  REACTION WITH WATER AND INDICATOR

  REACTION WITH SODIUM HYDROXIDE

  REACTION WITH SODIUM CARBONATE

  ESTERIFICATION REACTION

  REACTION WITH NEUTRAL FERRIC CHLORIDE
• REACTION WITH WATER & INDICATOR

  • acetic acid

  1. blue to red
  2. pink solution

  • stearic acid

  1. blue to red
  2. orange solution
• carboxylic acids exhibit acidic property in aqueous solution
• acidity of carboxylic acids can be detected through pH measurement, the use of pH paper or pH indicators
• REACTION WITH SODIUM HYDROXIDE

  • acetic acid soluble,

  1. clear colorless solution

  • stearic acid insoluble,

  1. clear colorless solution with insoluble white layer
• carboxylic acids react with strong bases (such as sodium hydroxide or potassium hydroxide) forming water-soluble salts as products (neutralization)
• REACTION WITH SODIUM CARBONATE

  acetic acid

  1. positive FORMATION OF EFFERVESCENCE
  2. no change after heating
• REACTION WITH SODIUM CARBONATE


  the reaction is accompanied by the formation of effervescence
• ESTERIFICATION REACTION

  • acetic acid

  1. pear-like odor

  • benzoic acid

  1. nutty-like odor
• • alcohols react with carboxylic acid in the presence of an acid catalyst (Fischer esterification)
  • protonation of the carbonyl oxygen which makes the carbonyl carbon electrophilic
• production of an ester is indicated by the presence of characteristic fruity-like odor
• REACTION WITH NEUTRAL FERRIC CHLORIDE

  • acetic acid

  1. turbid orange solution
  2. reddish brown precipitate

  • tartaric acid

  1. turbid orange solution
  2. reddish brown precipitate
• REACTION WITH NEUTRAL FERRIC CHLORIDE

  • function of test: can be used to detect the presence of carboxylic acid
  • reagent: neutral ferric chloride (ferric chloride in sodium carbonate)
  • positive result: reddish brown/brick red precipitate
• SPECIAL TEST FOR CITRIC AND TARTARIC ACIDS

  • citric acid

  1. green solution
  2. brown precipitate

  • tartaric acid

  1. violet solution
  2. brown precipitate
• citric acid 


  is tricarboxylic acid and has no enantiomer form

  • yield a green solution of alkaline manganate
• tartaric acid 


  dicarboxylic acid that has two enantiomer forms:

  D-tartaric acid and L-tartaric acid

  • brown precipitate of manganese dioxide will be produced
• SPECIAL TEST FOR CITRIC AND TARTARIC ACIDS

  established by Chapman and Smith
• FERRIC HYDROXAMATE TEST

  PRELIMINARY TEST

  FINAL TEST
• FERRIC HYDROXAMATE TEST

  PRELIMINARY TEST

  • ethyl acetate

  1. pale yellow-green solution

  FINAL TEST

  • ethyl acetate

  1. dark maroon solution
• FERRIC HYDROXAMATE TEST


  test to identify esters

  • intensely colored complexes
• esters are organic compounds with the general formula of R1C=OOR2 , where R1 may be hydrogen, alkyl or aryl groups and R2 may be an alkyl or aryl group but must not be a hydrogen
• • esters are very common in nature and are known to have characteristic pleasant odors unlike carboxylic acids
  • this property enables esters to be utilized as perfuming or flavoring agents, aside from them being used as organic solvents
• HYDROLYSIS REACTION

  • acetic anhydride

  1. blue to red
  2. evolution of heat

  • acetamide

  1. red to blue
  2. evolution of gas
• acid anhydrides are organic compounds with two acyl groups (RC=O) joined together by an oxygen atom
• amides are organic compounds with general structure of a nitrogen atom bonded to the carbonyl carbon atom (RC=ONH2 )
• acetamide produces carboxylate salt and free ammonia
• acetic anhydride can be hydrolyzed into two molecules acetic acid