L7. Saponification

Introduction:

Saponification is a reaction that produces soap when you mix and ester and NaOH. 

Material:

- 900 mL beaker.
- Spoon.
- Clock Glass.
- Balance
- stirring rod
- safety goggles
- gloves
- heating plate 
- 32 g NaOH.
- 90 mL H2O.
- 270 g recycled oil.

Procedure:

We mixed in a 600 ml beaker 32 grams NaOH with 90 ml of water, slowly, we noticed that the beaker heated up (it is a endotermic reaction) After that we slowly started to drop the olive oil in the beaker, at the same time mixing the mixture with the stirring rod. We mixed it for 20 minutes, also we heated the beaker on the heating plate to accelerate the reaction. Then we put a couple of drops of aroma and finally we put the soap mixture in a mold. 

L6. Lipids properties

Introduction: 

These compounds are characterized as natural substances that do not mix with water but dissolve in organic solvents, C, H and O are the principal elements of lipids. There are several classes of lipids including: fatty acids, waxes, triacylglycerols, phospholipids, terpens and steroids. Lipids are made in general of long chains of hydrocarbons with relatively little oxygen.  

Material: 

- test tube rack
- 250 mL beaker
- water
- 6 test tube 
- cellulose paper
- dropper
- glass rod
- oil 
- soap 
- milk (semi-skimmed, skimmed, without lactose) 
- petroleum ether
- ethanol 
- sudan III

Procedure: 

Solubility of some lipids:

1. Clean and dry three test tube. Label as W (water), ethanol (E) and PE (ether)
2. Add 3 drops of oleic acid to 3 small test tubes.
3. Add 1 mL of water in teh first test tube (W).
4. Add 1 mL of ethanol in the second test tube (E).
5. Add 1 mL of petroleum ether in the third test tube (PE).

Shake carefully each test tube and record solubility and observations in your worksheet.

Lipids identification:

      

 Translucent Mark:

1. Cut two pieces (10x10cm) of cellulose paper.
2. Put 1 drop of water in the first squared piece. You will see a transluced spot. Wait for a while and observe what is happening.
3. Put 1 Drop of olive oil in the second suqred piece of cellulose papaer. You will see a transluced spot. Wait for while and observe what is happening. Has the spot dissapered? Why?

Sudann III dye: 

(Sudan III is a red fat-soluble dye that is utilized in the identification of the presence of lipids, triglycerids and lipoproteins in liquids.)

1. Take the W test tube of the first experiment and add 2 drops of Sudan III.
2. Prepare four test tubes: 3 with milk with different fat content (M1, M2, M3) and soda (S). Add two drops of Suddan III and observe the results.

Permament emulsion:

1. Take a 250 mL beaker and put 100 mL water.
2. Add 1  mL of olive oil. With a glass rod stir the mixture vigorously and let it stand for a few minutes.
3. Make note of What is happening.
4. Add 2 drops of soap and stir the mixture again. Let it stand for a few minutes and notice the differences between both mixtures.

 Conclusions:

1. Solubility of lipids:

1. First test tube: water and oil didn't mix.
2. Second test tube: oil and and ethanol formed micelles
3. Third test tube:  oil and  ether (organic dissolvent) can dissolve.

2. Identification of Lipids
1. Translucent mark results: If we can see a mark in the celulose paper it's a lipid.
2. Sudan III: It doesn't work

3. Permanent emulsion formation

Water and oil form a monocape of

Questions
1- From your observation, wich compunds can dissolev lipids?

Ether

2- Do the oil and water mix? What can you conclude about the polarity of the oil if you know that water is polar? 

No, the oil is non polar

3- Why is liquid the olive oil at room temperature? And why not the lard?

Because oil is formed by unsaturated fatty acids. On the other hand lard is formed by saturated fatty acids.

4- Why does the lipid leave a translucent spot on paper?

Because the lipid does not evaporate.

5- Wich type of milk contains more lipids? Why?

Milk full-cream, because they take away the semi-skimmed milk fats.

6- Did the oil and water mix when you added the soap?

No, but a monolayer and a micelles separated oil from water formed.

7- What did the soap do to the fat?

Separated in micelles.

8- Can you think about process and locations were compounds like the soap would be important to an animal? 

Biliar acids.

L5. Fehling's test reducing sugars

Introduction:

Fehling's solution is a chemical test used to different between reducing and non-reducing sugars. This test is based on the reaction of a functional group of sugar molecules with Fehling's reagent.

Fehling's A: is a blue aqueous solution of copper (II) sulphate. 
Fehling's B: clear and colourless solution of potassium sodium tartrate and sodium hydroxide.

When a sugar has reducing ability, the mixture turns from deep blue colour to green colour suspension with a red precipitate. Some sugars are capable of reducing copper II ions to copper I ions. This reducing ability is useful in classifying sugars. When the sugar to be tested is added to the Fehling's solution and the mixture is heated, some sugars can be oxidized (to lose electrons) and the Fehling's mixture can obtain this electrons (reduced)

Material: 

- Test tube rack
- 10 ml pipet
- Distilled water
- 5 test tubes
- 5 spatula
- Lactose
- Maltose
- Glucose
- Sucrose
- Starch
- Fehling's A and B
- HCl

Procedure: 

In this experiment you will first determine with sugars give a positive test Fehling's reagent and then, by testing the reaction of some organic molecules containing onlya single functional group, you should be able to deduce which functional group of sugar is reacting with Fehling's reagent:

1. Take 5 test tubes and label: G, M, S, L, ST.
2. Put 2 mL of distilled water inside each tuve.
3. With different spatulas put a small amount of each sugar. Dissolve the sugar.
4. Add 2mL of Fehling's A solution and then Fehling's B.
5. Place each test-tuve in a boiling water bath (250mLbeaker on a hotplate stirrer).
6. Observe what is happening.

Starch Hydrolysis:
Hydrolysis is the reaction of a compound with water. As you know, starch is a polymer, consisting of many units of α-D-glucose covalently linked together.

1. Place 2mL of 1% starch in a test tuve and add 0.5mL of 3M HCl. Mix and place this mixture in a boiling water bath for 10 minutes.
2. After 10 minutes, remove the tuve from the water bath and let it cool. Neutralize this solution with 1M NaOH and mix well.
3. Transfer 8-10 drops of this solution to a small test tuve.
4. Add 1mL of Fehling's A solution and 1mL of Fehling's B.
5. Heat for a few minutes in a boiling water bath.
6. Record your observations. Compare the results of this test with your results for unhydrolyzed starch in the step 1 of this experiment.
7. You can test the absence of starch with iodine solution too.       

Questions:

1-From your observations and the structures of the sugars given above, indicate which functional group in the sugar molecules reacts with Fehling's reagent.

 

The OH group is the one that reacts with Fehling's reagent because when it is free the sacharide will have the reducing power.

If the bond is monocarbonilic the sacharide will have reducing power, that's why all monosacharides have it (the OH from the C1 is always free).

 

2-Compare the results you obtained for the Fehling's test of starch and Fehling's test of hydrolyzed starch. Explain your results.

I haven't done the Fehling's test of hydrolized starch but i can deduce it:

In the Fehling's experiment the starch doesn't have a reducing power because the OH is not free but when the starch is hydrolyzed it turns into glucose and glucose has a free OH because it's a monosacharide. Also the last glucose of the starch chain will have a reducing power (the ones that are in the ends).

The starch components are alfa D glucoses: amylose alfa (1 -> 4) linear chain, and amylopectine alfa (1->6) ramifications.

3- Would have you obyined a Fehling's positive test if you had hydrolyzed the sucrose (as you have done with starch9? Why?  

If we hydrolize the sucrose, we break the o-glycosidic bond. The two monosaccharides that formed sucrose (glucose and fructose) would react with Fehling reagent and then the reaction will be positive becuase monosaccharides have reducing power.

4-  What does "reducing sugars" term mean?

A reducing sugar is the one that reacts positive to the Fehling's test. This means that they are capable of reducing coper II ions to copeer I ions. When the sugar to be tested is added to the Fehling's solution and the mixture is heated, some sugars can be oxidized (to lose electrons) and the Fehling's mixture can obtain the electrons (reduced).  


 

L4. Saccharides properties

Introduction: 

Saccharides are organic molecules consisting of C, H and O atoms. Usually the empirical formula is CnH2nOn. Are divided into three groups:

Monosaccharides: formed by a linear carbon chain, are the building blocks of oligo and polysacchariedes. They have a one functional group: cetone (C=O) or aldehyde (COH). Pentoses and hexoses can switch from acyciclic to cyclic forms called furanoses and pyranoses.

Oligosaccharides: small plymer containing between 2 and 10 monosacharides.

Polysaccharides: big polymers with more than 10 monosaccharides.

These molecules perform numerous roles in living organisms like storage if energy, structural components.  Saccharides yield 4,2 kcal/g and are abundant in fruits, sweets, honey, beans, tubers, rice...

Material:

- Test tube rack
- 10 mL pipet
- Distilled water
- 5 test tubes
- 1 dropper
- 5 spatula
- lactose
- maltose
- glucose
- sucrose
- starch
- lugol's iodine

Procedure:

From Liza's blog

1. In the first part of the experiment we're going to test some physical properities of the saccharides you have in the lab: flavour, crystal structure and colour.

test solubility

1. Clean and dry 5 test tubes and label them "G, M, L, SU, S"
2. Put 5mL of water in each test tube.
3. With the aid of spatula, put a small amount of each saccharide inside the labelled test tube and test if they are soluble or insoluble.
4. Observe if each saccharide forms a mixture called dissolution or a colloidal suspension.

Lugol's iodine test:

1.  Finally, add 2 drops of Lugol's iodine to each test tube and test if the reaction positive or negative. Lugol's is a solution of elemental iodine and potassium iodine in water that is use to test a saccharide. The reaction is positive when iodine reacts by turning from yellow to purple, dark-blue/black colour.

Qüestions: 

1. Write the empirical formula of each saccharide that you have use. Show structures of the five saccharides. Classify each one in one group: mono, oligo or polysaccharide.

Starch: (C6H1006)n  polysaccharide
Glucose: C6H1006   monosaccharide
Maltose: C12H22011 disaccharide
Sucrose: C12H22011 disaccharide
Lactose:  C12H22011 disaccharide

2. Which of the monosaccharides are aldoses and which are ketoses?

Starch: aldose
Glucose: aldose
Maltose: aldose
Sucrose: ketoses
Lactose: aldose

3. Which bond links monosaccharides?

O-glycosidic

4- Which saccaharides are sweet?  Is this property related to the structure of the molecule?

glucose, maltose, sucrose. Yes becouse monosaccharides and saccharides are sweet.

5-  Which saccharides are insoluble? Is this property related to the structure of the molecule?

Starch is insoluble. If it's a big molecule is insoluble becouse it has a high molecular weight. 

6- Wich saccharide has reacted with Lugol's iodine solution?  

Starch.

7-  Which kind of food contains starch? 

 Flour, cereal, pasta, rice, legums...

8- Caculate the energy that comes from the saccharides 

23 g x 4,2 kcal= 96,6 kcal