ORGANIC CHEMISTRY
Experiment Fats and Oils
Aim
To estimate and compare the degree of saturation of sunflower oil and of olive oil.
Research Question
What are the relative amounts of KmnO4 (aq) required to oxidize the double bonds in olive oil and sunflower oil?
Introduction, Abstract and Hypothesis
When an organic compound has one or more double and/or triple bonds between two or more carbon atoms in its carbon chain, it is said to be unsaturated.
The higher the number of these double or triple bonds, the more the degree of unsaturation. Olive oil is mainly composed of oleic acid.
CH3(CH2)7CHñCH(CH2)7COOH
Sunflower mainly has in it linoleic acid.
CH3(CH2)4CHñCHCH3CHñCH(CH2)7COOH
Sunflower oil has two pairs of double bonds in its structure while olive oil has only one.
Acidified potassium manganate (VII) solution has the capability to oxidize such double bonds in ‘-ene’ groups. So it can oxidize the CñC bonds in these oils also.
In a reaction of these oils with acidified potassium manganate (VII) solution, sunflower oil would need more oxidizing agent that olive oil for a complete reaction since it has more number of double bonds than the oleic acid in olive oil.
In all probability, since sunflower oil has double the number of double bonds, it would need double the amount of the oxidizing agent as that required by olive oil.
So the hypothesis for this experiment was that in same volumes, sunflower oil would need more KmnO4 (aq) than olive oil to react completely.
Variables
Controlled
- Oil used
- Oxidizing agent
- Concentration the acid used
Independent
- Volume of the oil used
- Number of the double bonds in the oil
Dependant
- Volume of the potassium manganate (VII)
- The degree of unsaturation of the oils
Apparatus Used
| Sl. No. | Apparatus | Quantity |
| 1. | Conical flask (250 cm3) | 1 |
| 2. | Measuring cylinder (10 cm3) | 3 |
| 3. | Burette (50 cm3) | 1 |
| 4. | Retort stand | 1 |
Materials Used
| Sl. No. | Apparatus | Quantity |
| 1. | Cyclohexane | 60 cm3 |
| 2. | Sunflower oil | 60 cm3 |
| 3. | Olive oil | 60 cm3 |
| 4. | H2SO4 (aq) (2 mol dm-3) | 60 cm3 |
| 5. | KMnO4 (aq) | 50 cm3 |
Procedure
The burette was first filled with potassium manganate (VII) solution, its tap was ensured to be full, and the level of the upper meniscus of the liquid was kept at the 0 cm3 mark. The burette was then mounted on the retort stand.
Two sets of 3 experimental runs were carried out, the first set being for sunflower oil and the second one being for olive oil.
For each run the following were done in that order:
- The conical flask was properly washed.
- Cyclohexane, the oil and the H2SO4 (aq) (each 10 cm3) were added to the conical flask (in that order). The mixture was shaken well without spilling it.
- The initial reading of the burette was noted.
- The KMnO4 (aq) from the burette was added to the contents of the conical flask, a few drops at a time, while the flask was continuously being shaken vigorously, yet carefully.
- The tap of the burette was closed as soon as the contents of the conical flask were seen to remain pink permanently.
- The final reading of the burette was recorded.
The data for the sunflower oil was recorded in Table 18.1C and the data for the olive oil was recorded in Table 18.2C.
The data was collected in the following format.
| Sl. No. | Initial reading of the burette(v1/ cm3) (±0.05 cm3) | Final reading of the burette(v2/ cm3) (±0.05 cm3) |
| 1. | ||
| 2. | ||
| 3. |
Data Collection
Table 18.1C (for sunflower oil)
| Sl. No. | Initial reading of the burette (v1/ cm3) (±0.05 cm3) | Final reading of the burette (v2/ cm3) (±0.05 cm3) |
| 1. | 0.0 | 7.6 |
| 2. | 7.6 | 15.3 |
| 3. | 15.3 | 23.1 |
Table 18.2C (for olive oil)
| Sl. No. | Initial reading of the burette (v3/ cm3) (±0.05 cm3) | Final reading of the burette (v4/ cm3) (±0.05 cm3) |
| 1. | 23.1 | 30.0 |
| 2. | 30.0 | 37.0 |
| 3. | 37.0 | 43.9 |
Data Processing and Presentation
The titre values for each run were calculated.
Table 18.1P (for sunflower oil)
| Sl. No. | Initial reading of the burette (v1/ cm3) (±0.05 cm3) | Final reading of the burette (v1/ cm3) (±0.05 cm3) | Amount of KMnO4 (aq) used (v2-v1/ cm3) (0.05 + 0.05 = ±0.1 cm3) |
| 1. | 0.0 | 7.6 | 7.6 |
| 2. | 7.6 | 15.3 | 7.7 |
| 3. | 15.3 | 23.1 | 7.8 |
Table 18.2C (for olive oil)
| Sl. No. | Initial reading of the burette (v3/ cm3) (±0.05 cm3) | Final reading of the burette (v4/ cm3) (±0.05 cm3) | Amount of KMnO4 (aq) used (v4-v3/ cm3) (0.05 + 0.05 = ±0.1 cm3) |
| 1. | 23.1 | 30.0 | 6.9 |
| 2. | 30.0 | 37.0 | 7.0 |
| 3. | 37.0 | 43.9 | 6.9 |
Mean amount of KMnO4 (aq) used for sunflower oil = = 7.7±0.1 cm3
Mean amount of KMnO4 (aq) used for olive oil = = 6.93±0.1 cm3 ≈ 6.9±0.1 cm3
Conclusion and Evaluation
The results obtained from the titration runs showed that sunflower oil used up more KMnO4 (aq) than olive oil. This was consistent with a part of the proposed hypothesis. But the part of the hypothesis which stated that sunflower oil will use up double the amount of KMnO4 (aq) that olive oil was not proven. This may be due to the presence of some unbroken bonds in the linoleic acid in the sunflower oil. Using acid of a higher concentration and gently heating the reactants in a water bath could have helped these bonds to be broken.
It was necessary to add the KMnO4 (aq) drop-wise because the redox reaction involved was slow and required continuous mixing.
Courtesy: Mr.Balasubramanian – Teacher in Chemistry – HOD
For more IB chem. Exp contact balasb1234@yahoo.com
Filed under: Organic Chemistry
