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Topic: can a substance be protonated at home?  (Read 5836 times)

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Offline cestmoi

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can a substance be protonated at home?
« on: December 21, 2013, 01:09:06 PM »
 Specifically dl-lactic acid. I am during research on it microbicidal uses.

I have ordered a small sample of the dl-lactic acid from a chemist and I am curious
If there was some way I could protontate it myself.

 Or should I have a chemist do that?

Is it possible that the lactic acid is already protonated?

 I am new to the forum and not sure if this is the correct spot for this thread.

All answers are greatly appreciated!

Offline Archer

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Re: can a substance be protonated at home?
« Reply #1 on: December 21, 2013, 02:30:00 PM »
Specifically dl-lactic acid. I am during research on it microbicidal uses.

I have ordered a small sample of the dl-lactic acid from a chemist and I am curious
If there was some way I could protontate it myself.

 Or should I have a chemist do that?

Is it possible that the lactic acid is already protonated?

 I am new to the forum and not sure if this is the correct spot for this thread.

All answers are greatly appreciated!

It it's called "Lactic acid" then it is likely to be protonated. If it's called "Lactic acid sodium" or something weird like that then there is a strong chance that it is a salt.

Lactic acid is very water soluble without being a salt so I see no advantage to making it into a salt unless it is for a specific application.
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Offline cestmoi

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Re: can a substance be protonated at home?
« Reply #2 on: December 21, 2013, 11:34:45 PM »
Why do you say that it is "likely" protonated?

Is lactic acid usually protonated? Im not extremely familiar with the substance
and I don't know how familiar with it you are (you clearly know more than I do ;) )

But remember I have purchased dl-lactic acid, which is apparently the combination of d- lactic acid and l-lactic acid. Does that info give you any insight?

If I were to purchase l (+) lactic acid, does that plus symbol signify that it is protonated?
 
I have soo many questions I know, I can't express enough how grateful I am for your reply. THANK YOU THANK YOU THANK YOU!

Offline Borek

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Re: can a substance be protonated at home?
« Reply #3 on: December 22, 2013, 03:52:18 AM »
You seem to be confused about so many things I don't even know where to start.

Degree to which a weak acid (and lactic is a weak acid) is protonated in a solution is a function of the pH. pH can be result of the presence of the weak acid itself, it can be also forced on the solution by the presence of other acids or bases. In general the lower the pH, the more protonated the acid is, but it also depends on the acid identity (or, more precisely on its dissociation constant).

Lactic acid dissociates in water solutions. Lactic acid - when solid* - is fully protonated. When dissolved - it partially gets rid of these protons. Only partially, as it is a weak acid, that is not dissociating 100%. How much is dissociated depends on the concentration (and dissociation constant, but for a given acid it is - as the name implies - always the same). For example, if you dissolve 1g of lactic acid in 100 mL, around 3% will be dissociated (so not protonated), rest is protonated.

Lactic acid molecules are neutral. When they dissociate

HLactate ::equil:: H+ + Lactate-

they produce H+ and Lactate- anion. The neutral form on the left is the protonated one.

dl means racemic mixture. Lactic acid has two optical isomers (its molecules can take two forms, each of them rotates polarized light in a different direction). One of these isomers is designated l, the other d. dl means both isomers are present in the mixture is equal amounts. (+) in this context means exactly the same thing as d. Note that dl and DL are not equivalent (even if they refer to the same thing). l(+) doesn't make sens, L(+) can be correct.

As (+) in the name refers to the polarized light rotation, in the context of naming it has nothing to do with the acid protonation.

*Solid or liquid, as it depends. If there is only one optical isomer, lactic acid melts in much higher temperature than the mixture. Mixture is a liquid at room temperature, while single isomers melt at 53°C.
« Last Edit: December 22, 2013, 06:09:15 AM by Borek »
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Offline cestmoi

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Re: can a substance be protonated at home?
« Reply #4 on: December 22, 2013, 09:59:05 AM »
You seem to be confused about so many things I don't even know where to start.

Degree to which a weak acid (and lactic is a weak acid) is protonated in a solution is a function of the pH. pH can be result of the presence of the weak acid itself, it can be also forced on the solution by the presence of other acids or bases. In general the lower the pH, the more protonated the acid is, but it also depends on the acid identity (or, more precisely on its dissociation constant).

Lactic acid dissociates in water solutions. Lactic acid - when solid* - is fully protonated. When dissolved - it partially gets rid of these protons. Only partially, as it is a weak acid, that is not dissociating 100%. How much is dissociated depends on the concentration (and dissociation constant, but for a given acid it is - as the name implies - always the same). For example, if you dissolve 1g of lactic acid in 100 mL, around 3% will be dissociated (so not protonated), rest is protonated.

Lactic acid molecules are neutral. When they dissociate

HLactate ::equil:: H+ + Lactate-

they produce H+ and Lactate- anion. The neutral form on the left is the protonated one.

dl means racemic mixture. Lactic acid has two optical isomers (its molecules can take two forms, each of them rotates polarized light in a different direction). One of these isomers is designated l, the other d. dl means both isomers are present in the mixture is equal amounts. (+) in this context means exactly the same thing as d. Note that dl and DL are not equivalent (even if they refer to the same thing). l(+) doesn't make sens, L(+) can be correct.

As (+) in the name refers to the polarized light rotation, in the context of naming it has nothing to do with the acid protonation.

*Solid or liquid, as it depends. If there is only one optical isomer, lactic acid melts in much higher temperature than the mixture. Mixture is a liquid at room temperature, while single isomers melt at 53°C.


 YOU ARE AMAZING. THANK YOU SO VERY MUCH.

 OK you seem quite knowledgeable on this subject, so just a few more questions if that's ok..

I'm going to copy and paste the product details (which I shouldve done in the first place). Could you take a look and see if they give you any clues with the protonation ofthis substance? Also I noticed that it is NOT in a solid form, has it been neutralized?

Its critical that this stuff Is protonated!

Product details  Assay: 87.5-88.5% w/w.  Description: Natural L(+)-lactic acid, which is produced by fermentation from carbohydrates.

Form: liquid
Molecular formula: CH3CHOHCOOH
Molecular weight: 90
Chemical name: 2-hydroxypropionic acid

CAS number: 79-33-4 (general 50-21-5) USA GRAS

 Solubility: comletely soluble in water and alcohol. 

pH (approximate values!  You must do your own pH test!): 100% : pH 0.6  10%: pH 1.90    5%: pH 2.15    3%: pH 2.20    1%: pH 2.40

 You must use an alkaline pH adjuster to bring to pH UP to 3.5 Usage: Lactic acid and lactates can best be added in the aqueous phase. The presence of lactic acid depends on the pH.  The benefits and usage levels of lactates depend on the desired functionality: pH-regulation: < 0.5%           Moisturizing: 0.5 - 5 %    AHA effect: pH 4.0 - 5.0Skin lightening: pH 3.5 - 7.0

Restrictions: Do not use more than 10%Final formulation pH no less than 3.5CTFA recommends the addition of an SPF for AHA formulations.Alternatively you MUST wear a HIGH UVA and UVB sun protection product Storage: Cool, dry place. Do not freeze. Keep away from light and moisture!

Offline Borek

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Re: can a substance be protonated at home?
« Reply #5 on: December 22, 2013, 11:13:13 AM »
What is the intended application? Have you read the forum rules?
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Offline cestmoi

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Re: can a substance be protonated at home?
« Reply #6 on: December 22, 2013, 11:28:09 AM »
What is the intended application? Have you read the forum rules?

 Yes I have perused the forum rules. Did I violate one of them?

 I know the product description references cosmetics in some sort of way, but I AM NOT attempting to make my own cosmetics or medicines or anything of the sort! Sorry for any confusion!

 This is for research purposes!

 BUT did the product description give you any insight on the protonation of this liquid gorm of L (+) lactic acid?

 Once again thank you

Offline Borek

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Re: can a substance be protonated at home?
« Reply #7 on: December 22, 2013, 03:41:28 PM »
I AM NOT attempting to make my own cosmetics or medicines or anything of the sort!

Now it is a question of whether I believe, or not. Let's say its Christmas time and I am ready to show my better side  ;D

As I wrote before - whether is is protonated or not is only a matter of pH. The lower the pH, the more lactic acid is protonated. At pH 3.86 50% is protonated. At pH 2.86 10% is protonated. At pH 1.86 1% is protonated. At pH 0.86 0.1% is protonated. That's GenChem101 for you.
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Offline Archer

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Re: can a substance be protonated at home?
« Reply #8 on: December 22, 2013, 08:44:53 PM »

Product details  Assay: 87.5-88.5% w/w.  Description: Natural L(+)-lactic acid, which is produced by fermentation from carbohydrates.


hypothetically speaking, how are you intending to check the product from the fermentatiom?

Quote
Assay: 87.5-88.5% w/w
suggests that some sort of analytical instrumentation. I am not sure that pH alone will be sufficient. try brewing several batches of beer with that level of tollerance.

If it's any help fermentations are surprisingly difficult to obtain reproducable results without carefully monitored reaction conditions (look at rising bread in ovens set at different temperatures.
“ I love him. He's hops. He's barley. He's protein. He's a meal. ”

Denis Leary.

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