Organic acid, water solubility

Re: Organic acid, water solubility

wouldn't butanol be most acidic? acidity is determined based on the stability of the conjugate base, so the more stable the conjugate base (meaning weak base) would result in a stronger acid. butanol generates an alkoxide ion and it is a primary alcohol which would have a relatively low pKa (oxygen is more electronegative than nitrogen obv).

Re: Organic acid, water solubility

For your first question, recall what a Lewis acid is: a proton donor in water. Since butanol is the only molecule with a hydroxyl group in the list, it's the most likely to donate a proton. The others are either straight hydrocarbons or amines, which have more of an issue with letting go of their hydrogen: N-H bonds are less polar than O-H.

As for the second question: You have two hydroxyls on opposite carbons with the fourth molecule (1,2-ethylenediol), which means that the molecule as a whole is nonpolar. Propanol and butanol both have hydrocarbon chains opposite the hydroxyl group that don't like being in water, and the ether has two free electron pairs off of the oxygen lending itself to a partial dipole of the molecule. Since you've told us that the answer is not propanol, and butanol with its longer chain is probably less soluble, we're between the ether and the diol. The ether molecule is polar and the diol is nonpolar, so the answer is methyl ethyl ether (the second one).

Re: Organic acid, water solubility

my bad, instead of butanol its just butane for both questions

Re: Organic acid, water solubility

I looked up propanol and apparently propanol's hydrocarbon chain is not big enough to offset the electronegativity of the OH group, making this molecule fairly miscible in water. Longer carbon chain alcohols, 5C+ are not miscible for this reason.
I just don't understand why Propanol<methyl ethyl ether in water solubility. It should be close but is this simply suppose to be memorized?

My explanation for acidity was that N is more electronegative than C, Double bonds are proton receivers.

Re: Organic acid, water solubility

Okay, when you put butane in place of butanol, that's a tougher call. In this case, I suggest you see your professor during office hours to sort this out. Teachers are humans, too--they do make typos on their tests or enter the wrong answer into the key.

Re: Organic acid, water solubility

except that polarity isn't the only thing. plus ethers are barely polar...
the diol is by far more soluble in water, because of its ability to hydrogen bond.