Solubility of chlorophyll and carotenoids

[Puchinita5]

Homework Statement

okay. so i did a chromotography experiment with spinach leaves. A line of pigments separated from the spinach leaves was put on the chromatography paper. Then the paper was put in petroleum ether.

It showed carotene at the top, followed by xanthophylls, then chlorophyll A, then chlorophyll B. Therefore, I concluded that the carotenoids are less polar than the chlorophylls and is more soluble than chlorophylls.

THEN, and this is what makes no sense to me, we mixed a solution of ethanol and pigment with petroleum ether, shook it, and two layers formed. A dark dark layer and a yellowish layer. The p.ether was said to be at top because it was less dense.

WHY does chlorophyll separate into the p.ether while the carotenoids separate into the ethanol , whereas in the first experiment it was the other way around?! I would expect that the chlorphyll would dissolve more easily in ethanol and the carotenoids would separate into the petroleum ether.

Homework Equations

The Attempt at a Solution

 

[Puchinita5]

i guess i could also ask the question, why would a non-polar pigment such as carotene dissolve more readily in a more polar substance (ethanol) rather than in a more non-polar substance (petroleum ether).

 

[chemisttree]

Carotene is known to http://pubs.acs.org/doi/abs/10.1021/ja01326a056" in plant tissues.

Remember that these essential oils and oily pigments are present in plant tissues which is an aqueous environment. Is it likely that water-insoluble compounds like carotene exist in pure form or as microemulsions associated with natural surfactants in plant tissues? How about in your extraction?

Compare the structure of chlorophyll with that of a typical surfactant. Do you see a non polar tail and a polar head?