161: #5 Saponification and Iodine Number

Lipids

Heterogenous tissue components

Lipids

Bulk of organic matter of living cells with protein and carbohydrates

Esters

Lipids are actual or potential ____ of fatty acids.

Carboxylic acid; Alcohol

Many lipids result from the chemical reaction oof a ____ with an _____

Triglycerides

Esters formed from one molecule of glycerol (an alcohol) and three fatty acid molecules (carboxylic acids)

Insoluble

Lipids are ___ in water

Soluble

Lipids are ___ in fat solvents (ether, chloroform, hot alcohol, and benzene)

Simple Lipids

Esters of fatty acids with various alcohols

Compound Lipids

Esters of fatty acids with alcohols and a phosphate, carbohydrate or nitrogenous component

Derived Lipids

Derivatives obtained by the hydrolysis of simple and compound lipids.

Detection of certain characteristic groups

Analysis of lipids includes _____ based on their reactions with various reagents.

Saponification Number and the Iodine Number

Two determinations applied to fats demonstrating following properties of fats:

• Solubility in organic solvents

• Formation of emulsion

• Hydrolysis of fats to their constituent substances

Saponification

Process wherein fats are boiled with

alkali, producing glycerol and the metallic salt of the fatty acid (i.e., soaps).

Sodium

→ Hard Soaps

Potassium

→ Soft Soaps

RCOOH + KOH

Fatty acid + Potassium hydroxide

(Palmitic acid)

→ RCOOK + H2O

→ K salt of fatty acid + H2O

(Potassium palmitate)

Saponification Number

Number of mg of KOH required to neutralize the fatty acid liberated in the saponification of 1g fat or oil.

Saponification Number

It is a measure of the mean molecular weight (or

chain length) of all the fatty acids present in the

sample in the form of triglycerides.

True

TRUE OR FALSE: The 3 moles of fatty acids in a mole of triglyceride will neutralize 3 moles of KOH per mole of triglyceride split.

↑ Saponification Number

= ↓ Average Molecular Weight of Fatty Acid

Saponification Number

The average molecular weight of the fatty acid may be calculated directly from the ____.

known amount of KOH in alcohol

In the determination of the saponification number, a _________ is used to split the ester linkages of the triglycerides.

neutralize the freed fatty acids

The excess KOH over and above required to ______ is determined by titrating to a phenolphthalein end point.

difference

The saponification number is then calculated from the _____ in the amount of standard HCl needed to neutralize a known volume of KOH in the blank and the excess KOH in the solution containing the sample of fat.

Saponification Number Formula

(𝑉𝑜𝑙. 𝑜𝑓 𝐻𝐶𝑙 𝑖𝑛 𝑏𝑙𝑎𝑛𝑘 − 𝑉𝑜𝑙. 𝑜𝑓 𝐻𝐶𝑙 𝑖𝑛 𝑠𝑝𝑒𝑐𝑖𝑚𝑒𝑛) × 𝑁 𝑜𝑓 𝐻𝐶𝑙 × 56.1 / 1.5 × 𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝑔𝑟𝑎𝑣𝑖𝑡𝑦 𝑜𝑓 𝑠𝑝𝑒𝑐𝑖𝑚𝑒𝑛

1st Step of Identifying the Unknown Oil Sample

Compute for the saponification number using the specific gravity of each possible oil. If the given specific gravity is in a range, try random values within the range.

Castor Oil

179 - 185 Saponification Number

Corn Oil

188 - 193 Saponification Number

Olive Oil

190 - 195 Saponification Number

Coconut Oil

255 - 258 Saponification Number

2nd Step of Identifying the Unknown Oil Sample

Compare the computed saponification number with the theoretical range of saponification number for each type of oil.

3rd Step of Identifying the Unknown Oil Sample

Choose the type of oil where the computed saponification number is closest to or falls within its theoretical range.

Double bonds (unsaturated lipids/fats); point of unsaturation

When fats containing ____ are treated with iodine, bromine, iodine bromide or iodine chloride, the double bonds become halogenated. They will add a halogen at the.

Iodine Number

Number of grams of iodine required to saturate 100g of unsaturated fat.

Iodine Number

A measure of the relative degree

of unsaturation of a fatty acid.

Wijs Method

Uses Iodine Chloride (ICl) as a carrier

Rosenmund-Kuhnhenn Method

Uses a pyridine sulfate dibromide solution

Hanus Method

Uses Iodine Bromide as carrier. Mainly determines the excess bromine remaining in the solution after the sample was reacted with a known amount of bromine (blank).

TITRATION SUMMARY

Amber/Brown → Light Yellow → Add starch → Blue → Colorless

Iodine Number Formula

(𝑉𝑜𝑙𝑜𝑓𝑁𝑎 𝑆 𝑂 𝑖𝑛𝑏𝑙𝑎𝑛𝑘−𝑉𝑜𝑙𝑜𝑓𝑁𝑎2𝑆2𝑂3 𝑖𝑛𝑠𝑝𝑒𝑐𝑖𝑚𝑒𝑛)×𝑁 o𝑓 𝑡𝑖𝑡𝑟𝑎𝑛𝑡 × 12.69 / 0.3 × 𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝑔𝑟𝑎𝑣𝑖𝑡𝑦 𝑜𝑓 𝑠𝑝𝑒𝑐𝑖𝑚𝑒𝑛

1st Step in Identifying the Unknown Oil Sample of Iodine Number

Compute for the iodine number using the specific gravity of each possible oil. If the given specific gravity is in a range, try random values within the range.

2nd Step in Identifying the Unknown Oil Sample of Iodine Number

Compare the computed iodine number with the theoretical range of iodine number for each type of oil.

3rd Step in Identifying the Unknown Oil Sample of Iodine Number

Choose the type of oil where the computed saponification number is closest to or falls within its theoretical range.

Olive Oil

75 - 95 Iodine Number

Coconut Oil

8 - 9.5 Iodine Number

a)  Solubility in water

Which of the following is NOT a characteristic of lipids?

1. a)  Solubility in water

2. b)  Insolubility in water

3. c)  Solubility in fat solvents

4. d)  Esters of fatty acids

b)  Simple lipids, compound lipids, and derived lipids

What are the three types of lipids based on their composition?

1. a)  Fats, oils, and waxes

2. b)  Simple lipids, compound lipids, and derived lipids

3. c)  Phospholipids, glycolipids, and sterols

4. d)  Saturated, unsaturated, and trans fats

d)  Nitrogenous base

Which component is NOT included in the structure of compound lipids?

1. a)  Fatty acids

2. b)  Alcohols

3. c)  Phosphate

4. d)  Nitrogenous base

c)  Derived lipids

Which type of lipid is formed by derivatives obtained by the hydrolysis of simple and compound lipids?

1. a)  Simple lipids

2. b)  Compound lipids

3. c)  Derived lipids

4. d)  Phospholipids

c)  Solubility in organic solvents and hydrolysis of fats

Which properties of fats are demonstrated in the determination of saponification number and iodine number?

1. a)  Solubility in water and formation of emulsion

2. b)  Formation of emulsion and hydrolysis of fats

3. c)  Solubility in organic solvents and hydrolysis of fats

4. d)  Solubility in organic solvents and formation of

   emulsion

a)  Wijs Method

Which method for determining iodine number uses iodine monochloride (ICl) as a carrier?

1. a)  Wijs Method

2. b)  Rossenmund-Kuhnhenn Method

3. c)  Hanus Method

4. d)  None of the above

b)  Iodine number

In the Hanus Method, what is primarily determined by measuring the excess bromine remaining in the solution after the sample reacts?

1. a)  Amount of saturated fats

2. b)  Iodine number

3. c)  Unsaturated fatty acids

4. d)  Presence of impurities

a)  Position of the double bond

Which factor primarily determines a double bond's ability to add halogen in the determination of iodine number?

1. a)  Position of the double bond

2. b)  Temperature of the reaction

3. c)  Length of the fatty acid chain

4. d)  Concentration of the halogen reagent

c)  To avoid interference from light-sensitive reagents

Why is the reaction and titration in the Hanus Method performed in relatively dark conditions?

1. a)  To prevent excess bromine

2. b)  To stabilize iodine radicals

3. c)  To avoid interference from light-sensitive reagents

4. d)  To accelerate the reaction rate