ochem: solubility

[HoangDDS]

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Dimethylpropylamine (N, N-dimethyl-1-propanamine)
will be least soluble in which of the following?
A. dilute KOH(aq)
B. dilute HCl(aq)
C. dimethyl ether
D. benzene
E. concentrated H2S04

answer is A.

how do I approach to solve this problem? What was the rule for solubility regarding ochem reagents? Is there anything else besides likes dissolve likes?

So since dimethylproplamine is uncharged so I'm suppose to look for a reagent that is going to keep it uncharged? Because uncharged cmpd are least soluble?

Obviously, I'm still very confused. Thanks for any inputs.

 

[klutzy1987]

I think that in an acid it will take away a H+ and then form a ionic bond between the conjugate base and itself. In the nonpolar organic compounds it is soluble because it is also organic and and non polar. That leaves the base which will not react or mix with the amnie at all and therefore will be least soluble.

 

[HoangDDS]

I think that in an acid it will take away a H+ and then form a ionic bond between the conjugate base and itself. In the nonpolar organic compounds it is soluble because it is also organic and and non polar. That leaves the base which will not react or mix with the amnie at all and therefore will be least soluble.

Thanks Kltuzy. So I understand that in acid (B and E), it will be able to pick up a H+ and therefore becomes charged and that will be soluble in water to some extend--thanks. But I'm still confused on how we can eliminate choice C and D because they are organic compounds.

 

[harrygt]

Thanks Kltuzy. So I understand that in acid (B and E), it will be able to pick up a H+ and therefore becomes charged and that will be soluble in water to some extend--thanks. But I'm still confused on how we can eliminate choice C and D because they are organic compounds.

Klutzy is right, Hoang. I would elaborate a bit more. Deimethylpropyl amine is a slightly polar molecule just like benzene and ethers, and as you know, "likes dissolve likes"

 

[HoangDDS]

So since N can H-bonds with the organic molecules like choice C and D therefore it will become charged. And that will be soluble to some extent in water?

 

[klutzy1987]

So since N can H-bonds with the organic molecules like choice C and D therefore it will become charged. And that will be soluble to some extent in water?

Since like dissolves like, The n,n, dimethyl propyl amine will dissolve in Ether or benzene.

 

[harrygt]

THere is no H bonding [benzene and ethere don't have any hydrogens connected to F, O or N]. It is based on "like dissolves like"

 

[marscole]

YES!!! those are organic solvents that they used most!!! like cyclohexane, diethyl ether, benzene (not common now, coz it's too toxic), methanol, acetone...

i guess why it is least dissolved in KOH because your compound is a base... so.. it will least dissolve in base condition. the amine cant be protonated by OH-... this may be why it's least dissolve.. but doest mean will not dissolve... remember.. it's diluted... so... H2O must be present... small amount of H2O will dissociate and form H+ and OH-... H+ will then protonate the NH2...

hehehehe... hope it helps... 😀

 

[HoangDDS]

THere is no H bonding [benzene and ethere don't have any hydrogens connected to F, O or N]. It is based on "like dissolves like"

hehe. Thanks! I get it now. Just had to think about it a little bit.