[Jiro]

Question:
The acetone extract of red algae never seems to capture the predominant dark red colour of the living algae. Do you have an explanation for the disappearance of the colourization?

My Answer:
The acetone reacts in some way to rearrange the molecules of the living algae. This rearrangement constitutes a change in the planar sp₂ arrangement which causes such absorbance of light (dark red colour).

I don't think my hypothesis is right though.

[Froggirl]

This is bit of a vague question. There are heaps of possible answers but hey the way I look at it there are 2 most probable ones:

1. The dark red coloured compound in living algae just isn't soluble in acetone hence it wouldn't be present in the extract.

2. Somehow the colour has faded (as do many natural dyes). Some compounds can just degrade with time. Any change in molecular size, shape or bonding properties of the compound will effect its colour.

Its like flamingo feathers. Once they are plucked from a bird, with time they turn from bright pink to white since they no longer have a living system to replenish the pink colouration.

There is a third option but I don't think its very likely....

3. The acetone does has somehow reacted with the compound to cause a disappearance of colour.

I think your best bet is number one....as Occham's Razor states "all things being equal, the easiest answer is usually the correct one".

[Jiro]

hahaha awesome my prof just told me i was wrong.

"good hypothesis, and similar things are known to happen. Here, however, it is a case of polarity because red compounds are very polar, they do only get extracted by hot water"

[Mitch]

Acetone is polar though.

[Jiro]

perhaps... hahaha