lost
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solubility of naphthalene in acetone
I was wondering what is the explanation of the solubility of naphthalene (non-polar) in acetone (polar)? I though only non polar solvents whould
disolve other non-polar compounds
Thanks in advance ^^;;
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BromicAcid
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Acetone is not strictly polar or non-polar, just more polar then something like a saturated hydrocarbon. For example when it is used in the lab as a
solvent for cleaning glassware it is an excelent solvent for grease and such on ground glass joints, then when the grease is cleaned off with acetone
water can be used to wash off the acetone, being that acetone is misicible with water and acetone will also dissolve many non-polar compounds.
So really all I'm saying is that acetone dissolves napthalene due to its non-polar characteristics, check out solvent properties in tables online
for more information such as from :
http://www.metachem.com/tech/hplc-solvent.html
Where the solvents are compared on something called the polar index. By this system water is assigned a value of 10.2, by contrast carbon
tetrachloride, one of the kings of non-polar solvents is given a value of 1.6, acetone has a value of 5.4 so it falls in the middle region between
examples of a polar solvent and a non-polar solvent. Honestly I would consider it more non-polar then polar myself, I mean, it hardly dissolves
inorganic salts and even when it does the solutions are usuall non-conductive (as I recall).
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lost
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Thanks a lot for clearing out my doubt, I really appreciate your help
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woelen
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Remarkably, acetone dissolves KMnO4. I think that this dissolves ionically.
Acetone also dissolves CuCl2 quite well (both the hydrous and anhydrous stuff). The solution in both cases is brown/yellow, indicating that CuCl2 is
dissolved as molecule. On the other hand, CuSO4.5H2O and CuSO4 do not dissolve at all. Cu(NO3)2.3H2O also dissolves in acetone quite well, with a blue
color.
CoCl2 also dissolves, it gives a blue solution.
So, acetone does dissolve certain inorganic salts, but probably only the more covalent ones, such as CuCl2.
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unionised
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Naphthalene stinks.
From this one can conclude that it isn't very strongly bound in the crystal lattice. Given that it is quite happy to wander off from the crystal
into the air, is it any wonder that it wanders off into solution?
If the acetone is able to interact with it at all (for example by dipole/ induced dipole interaction between the polar acetone and the polarisable
naphthalene) then this will increase the solubility still further.
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12AX7
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But if that were true, it would be strongly soluble in strongly polar solvents such as water, which it isn't.
BTW, odor is a highly variable thing (check the odor threshold of methyl mercaptan and compare it to say, heptane), so just saying something stinks
doesn't say anything about its evaporation rate.
In the particular case of naphthalene, it does happen to have a high vapor pressure, even in solid state. This means nothing of crystal stability
because the molecules don't wander off wholesale until the melting point well above the boiling point of water!
Tim
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lost
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I couldnt really undestand why the substance I was given (which looked, smelled and had the same melting point as naphthalene) was soluble in acetone
and ether, I even started to doubt it wasnt really naphthalene....
Thank you all for your help!
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unionised
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"But if that were true, it would be strongly soluble in strongly polar solvents such as water, which it isn't. "
It is true and the reason that napthalene isn't very soluble in water is that the naphthalene molecules disrupt the bonding between water
molecules.
"BTW, odor is a highly variable thing (check the odor threshold of methyl mercaptan and compare it to say, heptane), so just saying something
stinks doesn't say anything about its evaporation rate. "
Involatile things don't stink; napthalene does; therefore naphthalene is volatile. Of course, not all volatile things have an odour. Some of the
uses of naphthalene(all rather old fashioned now) depend on it being volatile.
"In the particular case of naphthalene, it does happen to have a high vapor pressure, even in solid state. This means nothing of crystal
stability because the molecules don't wander off wholesale until the melting point well above the boiling point of water! "
Napthalene melts at 80C. What altitude are you at that water boils well below 80C?
The vapour pressure of a material is obviously determined by the relative stabillity of the vapour and the condensed states. That's the basis of
the Clausius Clapeyron equation. The relatively poor crystal binding energy is precisely why it is quite volatile.
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vulture
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Let's not forget that naphtalene has an aromatic system. This increases polarizability too. Maybe someone has a value for the dipole moment of
benzene, IIRC it was quite higher than normal hydrocarbons.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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unionised
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The dipole moment for benzene, like any other symetrical molecule, is zero.
Its dielectric constant (relative permitivity) is higher than typical saturated hydrocarbons (2.3 vs 2.0 for cyclohexane).
[Edited on 19-11-2005 by unionised]
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12AX7
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| Quote: | Originally posted by unionised
Napthalene melts at 80C. What altitude are you at that water boils well below 80C?
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Oops, read that wrong. Meant to say boiling point 
Tim
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unionised
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Who read what wrongly?
Anyway, the molecules are quite happy to leave the crystal at room temp- that's why its vapour pressure is high.
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vulture
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Sorry, was referring to dielectric constant ofcourse.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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franklyn
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Possibly mislabled
I used a .99 cent store bag of what I assumed was Napthalene moth balls.
These look and smell like crystaline Napthalene moth balls. The label says
Camphor ( made in Pakistan ). Camphor should be a waxy material , and
it's smell ( Vicks Vaporub ) is also distinctive , although similar to Napthalene.
The CRC handbook lists them both as having very similar solubility profiles in
common solvents. Whatever this was it dissolved somewhat with stirring
when microwaved in 90 % isopropanol , then sprayed as a fumigant.
The densities are diferent enough to resolve the question. Wikipedia reports
1.14 gm/cm³ for Naphalene and .99 gm/cm³ for Camphor. In my test the
ball sinks in water like a stone.
I'm going on the assumption that it looks and walks like a duck so its not
a pig.
Question : should I ignore the label and trust my nose. Is there a sure
way of determining what this is short of NMR.
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UnintentionalChaos
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Try heating a piece in boiling water. Camphor melts at 177-180C, napthalene melts at 80C. I think both will dissolve in hot alcohol (I know
naphthalene will since I just recrystallized some by doing that). An alternate name for naphthalene is "tar camphor" which may also be a source of
confusion.
[Edited on 10-27-07 by UnintentionalChaos]
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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franklyn
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It's napthalene
| Quote: | Originally posted by UnintentionalChaos
Try heating a piece in boiling water. Camphor melts at 177-180C, napthalene melts at 80C. |
That was obvious , silly of me to overlook that.
Thanks
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