Types of Titration

 

1. Aqueous Titration: 

 

Neutralization Reaction or Acid-Base Titration: It involves the titration of either acid with base (pH increases) or base with acid (pH decreases). It is of two types:

• Acidimetry: It is a measurement of the quantity of base by titration with a suitable standard acid (example: potassium hydrogen phthalate, oxalic acid, benzoic acid)

• Alkalimetry: It is a measurement of the quantity of acid by titration with suitable standard bases.  

Examples of Aqeous Titration of Organic Compound:

Titration of Monoprotic Organic Acids with NaOH (strong Base)

 

• Titration of benzoic acid with NaOH

• Titration of acetic acid with NaOH

2. Oxidation-Reduction Titration:

 

Example: Determination of Vitamin C Concentration by Titration (Redox Titration Using Iodine Solution)

Organic Compounds which generate free radical ions:

Compounds which does not contain electroactive substituents (Cation generation)

• Aromatic Hydrocarbons example: except benzene, radicals ions have been obtained from diphenyl and stilbene

• Heterocyclic compounds example: nitrogen heterocylces example pydridazine, tetrazine

Compounds contating electroactive substituents (Anion generation)

• Quinone

• Aromatic carbonyl compounds

• Carboxylic acid derivative

• Amines

• Nitrile
 

Electrochemical Methods in Organic Chemistry are used for:

• Oxidation and Reduction of organic compounds

3. Non-Aqueous Titration

       • Neither weak nor weak base can be easily titrated in aqeous solution due to dual behaviour of water as competing acid or base. The simple solution to this problem is to replace water as solvent. Hence, this type of titation is designed as non-aqeous titarion.

  

Acidimetry in Non-aqueous Titrations: It can be further sub-divided into two heads, namely:

•Titration of primary, secondary and tertiary amines with standard perchloric acid , and

• Titration of halogen acid salts of bases. 

Alkalimetry in Non-aqueous Titrations: titration of acidic substances

•Factors for performing non-aqeous titration: If

•Reactant is insoluble in water,

•Reactant is reactive with water 

Factors: for performing non-aqeous titration: If

•Reactant is insoluble in water,

•Reactant is reactive with water

Solvents Examples: Glycerin, Polyethelene glycol, alcohol

 Measuring the Endpoint or Equivalence of a Titration

 

•Indicator:

•pH Indicators

•Potentiometer

•pH meter

•Conductivity

•Color change

•Isothermal titration calorimeter

•Thermometric titrimetry

•Spectroscopy

•Amperometry

 

 Application

 

Particular Uses of TItration for Estimation Organic Compounds

Acid–base titrations

 

•In biodiesel: waste vegetable oil (WVO) must be neutralized before a batch may be processed. A portion of WVO is titrated with a base to determine acidity, so the rest of the batch may be properly neutralized. This removes free fatty acids from the WVO that would normally react to make soap instead of biodiesel. 

•Kjeldahl method: a measure of nitrogen content in a sample. Organic nitrogen is digested into ammonia with sulfuric acid and potassium sulfate. Finally, ammonia is back titrated with boric acid and then sodium carbonate. 

•Acid value: the mass in milligrams of potassium hydroxide (KOH) required to titrate fully an acid in one gram of sample. An example is the determination of free fatty acid content.

•Saponification value: the mass in milligrams of KOH required to saponify a fatty acid in one gram of sample. Saponification is used to determine average chain length of fatty acids in fat.

•Ester value (or ester index): a calculated index. Ester value = Saponification value – Acid value.

•Amine value: the mass in milligrams of KOH equal to the amine content in one gram of sample.

•Hydroxyl value: the mass in milligrams of KOH corresponding to hydroxyl groups in one gram of sample. The analyte is acetylated using acetic anhydride then titrated with KOH.

Redox titrations

•Vitamin C: Also known as ascorbic acid, vitamin C is a powerful reducing agent. Its concentration can easily be identified when titrated with the blue dye l.

Miscellaneous

•Karl Fischer titration: A potentiometric method to analyze trace amounts of water in a substance. A sample is dissolved in methanol, and titrated with Karl Fischer reagent. The reagent contains iodine, which reacts proportionally with water. Thus, the water content can be determined by monitoring the potential of excess iodine.

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