Description of experiment
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Needed compounds:
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acetyl chloride : CH3COCl
thionyl chloride : OSCl2
vanadium pentoxide : V2O5
Class:
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elem=C,Cl,V
coordination
Summary:
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Vanadium pentoxide does not dissolve in thionyl chloride, but when a small
amount of water is added, then it reacts.
Vanadium pentoxide dissolves in acetyl chloride, giving a dark red/brown
solution.
Description:
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Add a small amount of vanadium pentoxide to a ml of thionyl chloride: The solid
does not dissolve, not even the finest particles of the solid go into solution.
Add a drop of water: The water reacts with the thionyl chloride, giving HCl and
SO2, but now there also is a reaction with the vanadium pentoxide. A very dark
brown solution is obtained. Is this VOCl2 (or VCl4)?
It seems that the vanadium is reduced and that a deep brown vanadium(IV)
species is formed. On strong dilution, the liquid becomes blue, with a somewhat
green tinge. The blue color is from aqueous vanadyl ion, VO(2+), and the green
tinge most likely is because there also still is some vanadium in the +5
oxidation state, which is present as yellow VO2(+) ion.
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Add a small amount of vanadium pentoxide to a ml of acetyl chloride: The solid
partially dissolves, giving a deep brown solution.