Photosynthesis, a demonstration

It puzzled me: what made photosynthesis work?  The compound Chlorophyll is complex, was there a simpler system?  Chlorophyll contains a Magnesium ion complexed by a group similar to the haem group in haemoglobulin. The important point of this group is that it contains a carbon-nitrogen heterocycle.  So what simple compound has this, I chanced apon Pyridine which is a simple carbon-nitrogen heterocycle.

I made up a solution of roughly 300 ml distilled water and about 10 ml pyridine.  I then added about 5 grams of magnesium metal.

The magnesium metal dissolved in the solution with the evolution of hydrogen.  After a while all the metal had dissolved but the gas production in the form of bubbles continued.  On shading from the light of the sun the gas evolution stopped, starting again when the light was restored.

The solution was photo-lysing water with the formation of Hydrogen gas and Oxygen gas.

No further examination was attempted, the solution was washed down the sink.

Date of this experiment by Chris Strevens was about 1973.

Chris Strevens

Further Notes.

I would have thought that the pyridine and the magnesium would have to present in equimolar quantities.  The molecular weight of magnesium is about 26 and the molecular weight of pyridine is about 40 so a ratio of 2.6g of magnesium to 4g of pyridine would be right with about 1 liter of water.

The amounts taken above were almost random but I may have guessed the molecular masses of the two compounds.  No notes were taken during the experiment and it was more or less a chance observation.  I wondered what would happen.  I am writing from memory in 2000.

Chris Strevens.

Hit Counter