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Thread: why do some chemicals dissolve in ethanol

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    why do some chemicals dissolve in ethanol

    why do some chemicals dissolve in ethanol and some dont?? is it because of polarity where polar substances will only dissovle in other polar substances?

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    Member Sarebs's Avatar
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    Re: why do some chemicals dissolve in ethanol

    Yep.
    “It’s a matter of sorting out the wheat from the chavs.”

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    Re: why do some chemicals dissolve in ethanol

    Quote Originally Posted by SalButtsworth View Post
    why do some chemicals dissolve in ethanol and some dont?? is it because of polarity where polar substances will only dissovle in other polar substances?
    Ethanol dissolves a substantial number of substances due to its polar and non-polar nature. It has a polar hydroxyl group that can form h-bonds whilst there is an alkyl non-polar part that can form dispersion forces with grease and other non-polar substances.

    The point behind this dotpoint is that there are MANY substances that DISSOLVE in ethanol.
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    Re: why do some chemicals dissolve in ethanol

    because methylated spirits is 95% ehtanol. would the same property apply??

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    Prophet 9 FTW clintmyster's Avatar
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    Re: why do some chemicals dissolve in ethanol

    Quote Originally Posted by SalButtsworth View Post
    because methylated spirits is 95% ethanol. would the same property apply??
    it should.
    You should note that ethanol is domestically sold as methylated spirits.
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    Re: why do some chemicals dissolve in ethanol

    does anyone have a list of pure substances that dissolve in ethanol

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    Smile Re: why do some chemicals dissolve in ethanol

    Quote Originally Posted by SalButtsworth View Post
    why do some chemicals dissolve in ethanol and some dont?? is it because of polarity where polar substances will only dissovle in other polar substances?
    yes it is because of polarity.as polar molecules dissolve polar molecules(eg water a polar molecule dissolving ethanol also a polar molecule).and vice versa(eg tetrachloro methyl a non polar molecule dissolves in benzene also a non polar molecule)this is just a brief explanation but some how u asked and answer your question.

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    New Member adeyemi's Avatar
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    Re: why do some chemicals dissolve in ethanol

    Quote Originally Posted by SalButtsworth View Post
    does anyone have a list of pure substances that dissolve in ethanol
    all non polar molecules(molecules that have both ends alike)

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    Re: why do some chemicals dissolve in ethanol

    Actually, all polar + non-polar (in general) should be able to dissolve in ethanol, as it has a polar hydroxyl (OH) group, and a non-polar hydrocarbon chain - as "like dissolves like", ethanol can theoretically dissolve any covalent substance.

    As for the concept of "some do, some dont" - you are more likely thinking of water, which as a polar compound (due to the huge difference in electronegativity between oxygen and hydrogen) is only able to dissolve polar compounds.

    Ethanol is actually referred to as the "universal solvent" - which should give you an idea of its properties.

    Hope that helps.

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    *Rawr*! mitochondria's Avatar
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    Re: why do some chemicals dissolve in ethanol

    Quote Originally Posted by SalButtsworth View Post
    why do some chemicals dissolve in ethanol and some dont?? is it because of polarity where polar substances will only dissovle in other polar substances?
    Since the other part of your question was not answered (why some aren't soluble) I thought I might expand on it a little. (I'm clearly bored and procrastinating from... things.)

    Polarity, as you mentioned, is a fairly decent indication of what a solvent can or cannot solubilise. As Clinton has explained earlier, ethanol is a pretty good solvent for a lot of things because of the polar/non-polar duality that exists in the molecular structure of ethanol.

    In a sense, the polar and non-polar parts are, when both exist in one molecule, in a bit of a competition. At least for the water-alcohol series, the solubility of polar (or even ionic) substances decrease as you increase the chain length of the alkyl functionality.

    As a starting point, you can think of water as the most polar alcohol (it's technically not an alcohol because it doesn't have any hydrocarbon functionalities attached) - lots of salts are soluble in it as well as a lot of highly polar substances, such as NaCl. Extending this concept, the solubility of NaCl is much less when you move onto methanol because by introducing the methyl group you have substantially decreased the polarity of the solvent (if you are into a more technical description it's because methanol does not ionise to the same extent that water does - but that's out the scope for now!); and NaCl pretty much insoluble when you move onto ethanol.

    So the basic idea there is that every bit of the molecule counts - and the larger the non-polar bits the more the molecule likes interacting with non-polar things (sometimes even if the molecule have the appropriate bits but they are inaccessible [steric effects] or if there are other functional groups interfering [electronic effects] they may not have the solubility for things that you would expect). This is the basic idea that any good synthetic chemist would have a good grasp of! (I'm sure there are exceptions, such as strange things like ionic liquids - but, again, that's out of the scope of this discussion. )

    Back to your original question then - for ethanol, there are just as many soluble things as there are insoluble. To give you a rough idea, the following are some common substances that are insoluble or sparingly insoluble < 0.01 mol.L-1 (and they are either unreactive towards ethanol or the rate is simply too slow):

    • NaCl
    • Glucose (as well as a lot of sugars)
    • Some amino acids
    • Nucleic acids
    • Long-chain hydrocarbons



    Quote Originally Posted by SalButtsworth View Post
    because methylated spirits is 95% ehtanol. would the same property apply??
    Almost. Very subtle changes that shouldn't concern you at this stage. (It makes it a bit more polar - in some cases it makes a huge difference.)


    Quote Originally Posted by SalButtsworth View Post
    does anyone have a list of pure substances that dissolve in ethanol
    See above for some insoluble things. A general rule that I find useful is that if it's very small and doesn't have any very ionic bits (or sometimes lots and lots of polar bits), it's probably soluble in ethanol. (Having said that, I still find it strange that malonic acid isn't soluble in ethanol - so this rule isn't fool-proof )


    Quote Originally Posted by adeyemi View Post
    all non polar molecules(molecules that have both ends alike)
    No... Not really.



    Quote Originally Posted by adeyemi View Post
    Actually, all polar + non-polar (in general) should be able to dissolve in ethanol, as it has a polar hydroxyl (OH) group, and a non-polar hydrocarbon chain - as "like dissolves like"
    Nope.


    Quote Originally Posted by adeyemi View Post
    ethanol can theoretically dissolve any covalent substance.
    Nope, unless 0.0001 g.mol-1 is still considered as soluble...


    Quote Originally Posted by adeyemi View Post
    Ethanol is actually referred to as the "universal solvent" - which should give you an idea of its properties.

    Hope that helps.
    Since when is ethanol referred to as the universal solvent...? Water is known as the universal solvent, not ethanol...
    Last edited by mitochondria; 29 Nov 2009 at 2:35 PM.
    PhD Chemistry, UNSW
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    I hope that you have already attempted the question.

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    Re: why do some chemicals dissolve in ethanol

    Quote Originally Posted by mitochondria View Post
    Since the other part of your question was not answered (why some aren't soluble) I thought I might expand on it a little. (I'm clearly bored and procrastinating from... things.)

    Polarity, as you mentioned, is a fairly decent indication of what a solvent can or cannot solubilise. As Clinton has explained earlier, ethanol is a pretty good solvent for a lot of things because of the polar/non-polar duality that exists in the molecular structure of ethanol.

    In a sense, the polar and non-polar parts are, when both exist in one molecule, in a bit of a competition. At least for the water-alcohol series, the solubility of polar (or even ionic) substances decrease as you increase the chain length of the alkyl functionality.

    As a starting point, you can think of water as the most polar alcohol (it's technically not an alcohol because it doesn't have any hydrocarbon functionalities attached) - lots of salts are soluble in it as well as a lot of highly polar substances, such as NaCl. Extending this concept, the solubility of NaCl is much less when you move onto methanol because by introducing the methyl group you have substantially decreased the polarity of the solvent (if you are into a more technical description it's because methanol does not ionise to the same extent that water does - but that's out the scope for now!); and NaCl pretty much insoluble when you move onto ethanol.

    So the basic idea there is that every bit of the molecule counts - and the larger the non-polar bits the more the molecule likes interacting with non-polar things (sometimes even if the molecule have the appropriate bits but they are inaccessible [steric effects] or if there are other functional groups interfering [electronic effects] they may not have the solubility for things that you would expect). This is the basic idea that any good synthetic chemist would have a good grasp of! (I'm sure there are exceptions, such as strange things like ionic liquids - but, again, that's out of the scope of this discussion. )

    Back to your original question then - for ethanol, there are just as many soluble things as there are insoluble. To give you a rough idea, the following are some common substances that are insoluble or sparingly insoluble < 0.01 mol.L-1 (and they are either unreactive towards ethanol or the rate is simply too slow):

    • NaCl
    • Glucose (as well as a lot of sugars)
    • Some amino acids
    • Nucleic acids
    • Long-chain hydrocarbons





    Almost. Very subtle changes that shouldn't concern you at this stage. (It makes it a bit more polar - in some cases it makes a huge difference.)




    See above for some insoluble things. A general rule that I find useful is that if it's very small and doesn't have any very ionic bits (or sometimes lots and lots of polar bits), it's probably soluble in ethanol. (Having said that, I still find it strange that malonic acid isn't soluble in ethanol - so this rule isn't fool-proof )




    No... Not really.





    Nope.




    Nope, unless 0.0001 g.mol-1 is still considered as soluble...




    Since when is ethanol referred to as the universal solvent...? Water is known as the universal solvent, not ethanol...
    yes water is the only known universal solvent world wide.This is because it has d ability to dissolve more solute than other solvents

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    Re: why do some chemicals dissolve in ethanol

    As you know ethanol is C4 H5 0H, it is the OH molecule on the end that enables some substances to be dissolved by it, as OH has a valency of -1. Very good at dissolving grease ect. thats why alcohol is used in cleaning products hope it helps

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    Re: why do some chemicals dissolve in ethanol

    OH has a valency of -1
    this means nothing. the ability of ethanol to dissolve polar and non polar substances is directly related to the varying electronegativity of the C-H and the C-OH bonds.

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