it's definitely between not A and C, right? Because of the charge that the solvent would cause. Octanoic acid has 8 CH3 groups which are super nonpolar, so it's fairly unlikely to dissolve in water. therefore I would choose B. Message me if you have any questions. And yes, this would happen in the real world as well!
right, but octanoate also has 8 CH3 groups. so based on that, it also is fairly unlikely to dissolve in water, so you would choose both octanoate and octanoic acid as being more soluble in H2O than in CH2Cl2 in both cases. that's incorrect, though, for the MCAT and this question. so, you can't use that logic. you have to compare the octanoic acid with deprotonated caffeine and octanoate with protonated caffeine. in real life, yes, overall, octanoate is still overall more nonpolar than polar, but octanoate is more polar relative to octanoic acid. anyways, that's off topic and doesn't address the question.
the person who posted above your post is 100% correct. this question is based on "like dissolves like." what's more like polar water and what's more like nonpolar dichloromethane? the more polar of the 2 goes with water, the less polar of the two, thus more nonpolar of the 2, extracts with dichloromethane.
in basic extraction for the MCAT, when a compound gains charge, its water solubility goes up. when a compound loses charge, its water solubility goes down and organic solubility goes up.
so for this question, the charged compounds extracts with water, the aqueous layer, and the uncharged compounds extract with dichloromethane, the organic layer. the layer it extracts in is the layer it is more soluble in.
as a sidenote, in real life, I would think that octanoate would still separate into the organic layer because, as you said, the 8 CH3s still make it overall more nonpolar. for MCAT purposes, though, if it has an increase in charge, that charge is attracted to the polar water and extracts with the water into the aqueous layer. if it has a reduction in charge, it is less polar than it originally was so it extracts with the organic layer.
here's an example. let's say the original is +3 and changes to +2. on the MCAT, that would extract with the organic layer because it has a reduction of charge. in real life, though, I still see that as having A CHARGE thus being polar and extracting into the aqueous layer. I don't think the MCAT will ever put you in that situation, though. I think they will always keep you in between -1 and +1. That way, if you reduce in charge, you'll always go to 0, thus no overall charge, thus nonpolar, and thus organic layer.
EDIT: I said that example would not appear on the MCAT. I suppose it could and there would probably be a choice of "these compounds cannot be seperated" choice. I would go with that.
does anyone agree with me on that?
BTW, did anyone notice the mistake in the drawing of the acidic caffeine? they have the wrong charge. the N should be +1, not -1. the ammonia is protonated by the acid into ammonium. ammonium has a +1 charge. the answer is still the same because the caffeine still gains in charge in acidic solution, but it actually gains in positive charge, not negative charge. bad ExamKrackers.
