Author Topic: Preparation of Methane (PolytheneSam's pic transc)  (Read 2637 times)

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Aurelius

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Preparation of Methane (PolytheneSam's pic transc)
« on: January 17, 2003, 11:22:00 PM »
This is from PolytheneSam's pictures- aurelius has transcribed it.

Hydrocarbons of the Methane Series

Preparation of Methane from Sodium Acetate: Properties of Methane


Preparation of Methane:

Grind and mix thoroughly in a mortar 8g of fused sodium acetate (1) and 8g of soda-lime. (2)  Transfer the mixture to an 8” test tube provided with a rubber stopper fitted with a short piece of glass tubing.  Connect to the latter by means of a short rubber tubing a delivery tube arranged to collect gas over water.  Support the test tube, by means of a clamp, in such a position that the end containing the stopper is slightly lower than the other end; this prevents any water given off during the heating from running back into the hot tube and cracking it.  Heat the tube cautiously, keeping the flame in motion, in order to avoid local overheating.  Collect three 250cc bottles of the gas.  Prepare a mixture of the gas with air by putting into a fourth 250cc bottle 25cc of water; cover the bottle with glass plate, insert it in the pneumatic trough, and pass the gas into the bottle until the water has just been displaced.  Caution! :  Remove the delivery tube from the water before the heating of the tube is stopped.  If during the heating the water begins to go back into the test tube, the breaking of the latter can be prevented by separating the test tube from the delivery tube where they are joined together.

1.  Commercial fused sodium acetate is generally not anhydrous; it is well to fuse it before use.  If the compound is to be prepared from the hydrated salt (CH3COONa-3H2O) proceed as follows:  Heat cautiously about 15g of the crystalline salt contained in an iron pan over a small flame.  Stir continuously with a glass rod.  The salt melts at first in its water of crystallization, as the dehydration continues, it solidifies, and, finally, when anhydrous it melts again.  Care should be taken to avoid heating the dehydrated salt much above its melting point as it undergoes decomposition when strongly heated.

2.   The soda-lime can be replaced with and intimate mix of 4g of sodiumhydroxide and 4g of quicklime.

SPISSHAK

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You are a dedicated chemist
« Reply #1 on: January 18, 2003, 01:08:00 AM »

PolytheneSam

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What if you replaced the sodium acetate with...
« Reply #2 on: January 18, 2003, 01:17:00 AM »
What if you replaced the sodium acetate with the sodium salt of glycine, alanine, benzoic acid or para-aminobenzoic acid, to name a few?


SPISSHAK

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you know you
« Reply #3 on: January 18, 2003, 01:47:00 AM »
may be onto something sam, it looks like a facile procedure decarboxylating all kinds of amino acids, and carboxyl groups, I never could figure out where that extra hydrogen atom comes from that saturates whatever it is being decarboxylated as an alkali, or alkaline earth salt using an alkali base.
For example when you decarboxylate nicotinic acid with calcium oxide and heat to form pyridine.
Ok a carboxylic acid salt forms (removing the hydrogen atom from the acid function) and CO2 is given off leaving an unsaturated carbon where does that hydrogen atom come from?

PolytheneSam

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Maybe the hydrogen comes from a hydroxide in...
« Reply #4 on: January 18, 2003, 03:25:00 PM »
Maybe the hydrogen comes from a hydroxide in the mixture and the Na and Ca end up as carbonates (containing no hydrogen).  Notice that the process for making fused sodium acetate is there, too. 
PAA + AA  ---Na(OOCCH3)---> P2P