August 18, 2019, 09:49:51 PM
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### Topic: Caffeine extraction from tea  (Read 1198 times)

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#### Mimic

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##### Caffeine extraction from tea
« on: February 25, 2018, 04:09:18 AM »
In tea leaves, caffeine is present along with other compounds such as tannins and cellulose. Tannins are a class of compounds forming part of the esters, and by hydrolysis they form the corresponding acid, the gallic acid, and the corresponding phenol, glucose. Cellulose, on the other hand, is a polymer of glucose, practically insoluble in water.
The derivatives of tannins hydrolysis  can be precipitated as little calcium-soluble salts with the addition of CaCO3. So, gallic acid can be preciptated by the reaction

$$2 \ce{R-COOH + CaCO_{3}} \rightarrow \ce{(R-COO)_{2}Ca\downarrow + \; CO_{2} + H_{2}O}$$

Glucose can precipitate in the same way? If can do it, what is the reaction?

#### Borek

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##### Re: Caffeine extraction from tea
« Reply #1 on: February 25, 2018, 07:36:56 AM »
Gallic acid precipitates as a salt, glucose in general is not acidic and doesn't form salts.
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#### Mimic

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##### Re: Caffeine extraction from tea
« Reply #2 on: February 25, 2018, 07:51:13 AM »
So, glucose will be separated together with the cellulose during the extraction with diethyl ether?

#### Arkcon

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##### Re: Caffeine extraction from tea
« Reply #3 on: February 25, 2018, 09:51:00 AM »
In tea leaves, caffeine is present along with other compounds such as tannins and cellulose.

A clear fact, as stated.

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Tannins are a class of compounds forming part of the esters, and by hydrolysis they form the corresponding acid, the gallic acid, and the corresponding phenol, glucose.

That is one way to explain the relation between gallic acid and tannins.  But tannins are generally defined as polyphenoic compounds, sometime made up of gallic acid.  https://en.wikipedia.org/wiki/Tannin#Structure_and_classes_of_tannins  I don't know why you mention esters here -- one ester group makes something an ester, but the properties of a large molecule, with meany other groups, isn't the same those of a simple ester.

There's nothing technically wrong with what you've written, but stung together, you may be heading to incorrect conclusions.

https://en.wikipedia.org/wiki/Tannin#Structure_and_classes_of_tannins

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Cellulose, on the other hand, is a polymer of glucose, practically insoluble in water.

A clear fact, as stated.

Quote
The derivatives of tannins hydrolysis  can be precipitated as little calcium-soluble salts with the addition of CaCO3. So, gallic acid can be preciptated by the reaction

$$2 \ce{R-COOH + CaCO_{3}} \rightarrow \ce{(R-COO)_{2}Ca\downarrow + \; CO_{2} + H_{2}O}$$

An interesting fact that I didn't know.

Quote
Glucose can precipitate in the same way? If can do it, what is the reaction?

No.  Can you tell us why you think you can?  Do you think you have explained why you think it should be so in this thread?  Because when I split each statement up, you should be able to see there are non sequiturs.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.