hydrocarbons and functional groups

[rakuenso]

I read that functional groups that can be converted into charged species are able to overcoe the 5-carbon barrier to solubility in water. Why is it that a charged species is able to become soluble?

 

Also if the functional group is acidic (like COOH) do I add a base to give it a charge?

 

and the FG is basic (like NH2), do i then add a acid? [EDITED, lol original was quite idiotic]

 

What is relationship between being resonance stabilized and being more water soluble?

 

And does dissolving something mean that bonds are broken between molecules or within molecules

[Tetrahedrite]

I read that functional groups that can be converted into charged species are able to overcoe the 5-carbon barrier to solubility in water. Why is it that a charged species is able to become soluble?

Putting a charge on a molecule makes it highly polar (ie large positive and negative charges). Water itself is highly polar and therefore will dissolve other polar compounds readily.

 

Also if the functional group is acidic (like COOH) do I add a base to give it a charge?

Yes, for example benzoic acid (C6H5COOH) is only sparingly soluble in water, but addition of sodium hydroxide (the base) forms the benzoate ion (C6H5COO-) which is highly soluble in water.

 

and the FG is basic (like NH2), do i then add a base?

No, in this case you would add an acid.

 

What is relationship between being resonance stabilized and being more water soluble?

I don't believe there is a relationship, however I stand to be corrected.

 

And does dissolving something mean that the substance is being broken down into individual molecules in water?

Yes, each ion or molecule becomes "hydrated" or surrounded by a number of water molecules; electrostatic polar forces keep them apart.

[rakuenso]

alright thx alot, its clear to me now.

 

But now i've a technicality question

 

Say you add glucose(s) into water, and glucose molecules dissociate, then does that mean a reaction has occured.

 

Or is a reaction only when you add an acid/base to a functional group? would you write it as:

 

R-COOH(s) + NaOH (aq) -> R-COO(-)NA(+)(aq) + H2O(l)

[budullewraagh]

the glucose molecules dont ionize. they do become cyclic rings (through chemical change) upon addition to water

[akcapr]

wat r cyclic rings- is it hydrolyzed wen added to water?

[Yggdrasil]

The following reactions occur when glucose is in water. The cyclic hemiacetal forms (on the left and right) are favored over the straight-chain form (in the center).