Properties Of Carbohydrates

DATA COLLECTION

a) Dehydration

GLUCOSE

m = 0.5 g

OBSERVATION Change of state Color Viscosity Smell

Start Solid state. White color. No. No smell.

Action of heat Liquid state. Amber color. Yes. Smell of caramel.

Sulphuric acid Liquid state. White color. Yes. No smell.

Sulphuric acid + heat Liquid state. Black color. Yes. Smell of rotten eggs.

Sulphuric acid + strongly heated Solid state. Black color.

(Because of the gases volumen raises – we get charcoal.) No. Like setting on fire, because of SO2.

Table 1: Data collection from glucose in reaction known as dehydration

SUCROSE

m = 0.5 g

OBSERVATION Change of state Color Viscosity Smell

Start Solid state. White color. No. No smell.

Action of heat Liquid state. Amber color. Yes. Smell of caramel.

Sulphuric acid Liquid state. White color. Yes. No smell.

Sulphuric acid + heat Liquid state. Black color. Yes. Smell of rotten eggs.

Sulphuric acid + strongly heated Solid state. Black color. (Because of the gases volumen raises – we get charcoal.) No. Like setting on fire, because of SO2.

Table 2: Data collection from sucrose in reaction known as dehydration

In this part of experiment we should make also tests for CO, CO2, SO2. We did not do it but we told how we can do them:

- CO2 test: we put the mixture in lime-pit and blow inside. After that we should see white precipitation if CO2 is inside.

- CO and SO2 test we make so that we conduct them in water and then measure pH.

b) Oxidation

Carbohydrate Fehling 1 and 2 Observations at Fehling reaction Tollen`s reagent Observations at Tollens reaction

Sucrose Negative Stays blue Negative Colorless

Fructose Positive Orange- green Positive Silver mirror

Maltose Positive Orange- green Positive Silver mirror

Glucose Positive Orange- green Positive Silver mirror

Table 3: Data collection for carbohydrates in reaction known as oxidation

msucrose = 0.1 g

mglucose = 0.1 g

mmaltose = 0.1 g

mfructose = 0.1 g

c) Carbonyl derivates

GLUCOSE

m = 0.5g

The yellow crystals were formed immediately.

The white crystals were formed after 1 minute in the second part of the experiment.

FRUCTOSE

m = 0.5g

The yellow crystals were formed immediately.

The white crystals were formed after 1 minute in the second part of the experiment.

d) Hydrolysis of sucrose

Sucrose gives positive reaction with TollenÐ'Ò's reagent, because it is made of glucose and fructose and they give positive reaction – aldehyde and ketone.

e) Hydrolysis of starch

All test tubes give positive reaction with Fehling and Tollen`s reagent.

They also give positive reaction with iodine.

In this case the substance in test tube C became brown immediately, because it was already glucose in it.

In A, B, D test tubes, substance became first purple-blue when we add iodine (proof for starch contained), but after heating hydrolysis occurs and as a product we get glucose, which gives brown color with iodine.

CONCLUSION

Questions

a) DEHYDRATION

1. What are the main products when concentrated sulphuric acid reacts with glucose?

2. Why this reaction is called dehydration?