Reef Chemistry Question of the Day #166 Organic Carbon Dosing

Randy Holmes-Farley

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Reef Chemistry Question of the Day [HASHTAG]#166[/HASHTAG]

Which of the following organic compounds would likely be the worst choice for organic carbon dosing in a reef aquarium?

A. CH3CO2-O-CO2CH3
B. CH3CO2-O-CH2CH3
C. CH3CH2CH2OH
D. CH3CH2OH
E. CH3OH
F. CH3CO2H
G. CH3CH2CH3

Bonus: Why?

Good luck!























.
 

toaster77

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I am not sure what compounds A and B are with those formulas as written?

A. ?
B. ?
C. propanol
D. ethanol
E. methanol
F. acetic acid
G. propane
 
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Randy Holmes-Farley

Randy Holmes-Farley

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I am not sure what compounds A and B are with those formulas as written?

A. ?
B. ?
C. propanol
D. ethanol
E. methanol
F. acetic acid
G. propane

I'll give the names with the answer, if no one does before that (which someone proabably will).

Do you have a pick?
 

toaster77

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E (methanol) is likely to be the worst. It could be quite toxic due to metabolism to formaldehyde and formate.
 

Lynn52

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G propane because it is a gas at room temperature and atmospheric pressure.
 

redfishbluefish

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Thanks for a good little chuckle Randy.....I won't say the answer, but give the reason....it's not soluble in water and it has this uncanny tendency to go boom.
 

toaster77

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Indeed, propane would be ineffective as it is a gas at room temp and whatever small amounts are soluble in saltwater would be near impossible to be metabolized by most reef microorganisms (it could also mess up skimming!) However, if too much methanol is dosed you might start to seem some bad things happen to fish and corals...
 

redfishbluefish

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FYI, methanol is the carbon source of choice for the bacteria in Natureef's denitrification reactor.
 

toaster77

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Thanks for the info. Yeah, certain microorganisms could indeed oxidize methanol and reduce nitrates to N2 gas. I'm not up to date on how much of these carbon sources one needs to dose to see effects, but it's possible that too much (methanol) could be bad (at least to animals). Perhaps the amounts folks are using are well-tolerated by marine life.
 

Taservices

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my guess is G.

A would at least result in some acetic acid to use which we all know is standard.

B I have not the foggiest but it at least looks soluble

And other than G the others are all a certain category of compounds with which we commonly associate carbon dosing.

and then G as stated is propane is a gas at room temp, and relatively insoluble. (and flammable)
 

jason2459

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FYI, methanol is the carbon source of choice for the bacteria in Natureef's denitrification reactor.

Sulfur is also used in a reactor too for denitrification. I certainly wouldn't dose either directly to the tank. :)

I would hate to see a propane reactor though... :eek:
 

AllSignsPointToFish

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Ahh, a very good chemistry question.


A. CH3CO2-O-CO2CH3: looks like a peroxydicarbonate, an organic peroxide derivative. Can cause free radical formation as it is used as a radical reaction initiator. After hydrolysis, looks like it will form acetic acid. If the free radical half life is short, it may actually be okay in the aquarium. Very tricky, Randy :)
B. CH3CO2-O-CH2CH3: looks like a peroxyester. Also a free radical generator and would most likely not be good in an aquarium if the radical half life is very long. Decomposition products are likely to be acetic acid and ethanol after hydrolysis, so it may be okay in an aquarium.
C. CH3CH2CH2OH: propanol. May be toxic in larger quantities due to longer carbon chain, but could probably be metabolized by bacteria. Metabolic byproducts may be toxic, but I'm not quite sure. Normal propanol can be metabolized by marine bacteria, so it's probably okay.
D. CH3CH2OH: ethanol. Used all the time as an organic carbon. No issue here.
E. CH3OH: methanol. Used in industrial waste treatment to stimulate bacterial growth. No issue here. Ingredient in some products for aquarium use.
F. CH3CO2H: acetic acid. Also used in aquariums. No issue here.
G. CH3CH2CH3: propane. Not very soluble, so dosing would be difficult. However, there are marine bacteria that can metabolize alkanes, so it's probably not very effective carbon source but not a threat in low quantities either. Due to flammability, this is probably the worst carbon source to use in the aquarium as it won't readily be metabolized before it off-gasses.
 
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Randy Holmes-Farley

Randy Holmes-Farley

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I have to admit that I made a couple of typos on two chemicals on the list when I typed them out, but I'll discuss those and what I meant them to be when I discuss the answer.

Let's go with these choices for now. :)
 

DrDNA

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Aside from propane being flammable my guess is methanol since it can be metabolized into formaldehyde
 

beaslbob

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propane

flammable, not very soluable, sinks to the floor and can cause and explosion.

Great for bbq tho
 

Cory

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Id say E because of the OH raising ph
 
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Randy Holmes-Farley

Randy Holmes-Farley

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And the answer is...G. CH3CH2CH3 which is propane

Flammable gas, not very water soluble, and not easily metabolized by most bacteria. Probably not the best choice.

The names of them all are:

A. CH3CO2-O-CO2CH3 dimethyldicarbonate
B. CH3CO2-O-CH2CH3 ethylmethylcarbonate
C. CH3CH2CH2OH n-propanol
D. CH3CH2OH ethanol
E. CH3OH methanol
F. CH3CO2H acetic acid
G. CH3CH2CH3 propane

I actually meant the first two chemicals to be

A. CH3CO-O-COCH3 (acetic anhydride)
B. CH3CO-O-CH2CH3 (ethyl acetate)

Both of those should be readily hydrolyzed and metabolized, although they may take a bit of time to dissolve into seawater.

when I accidentally typed in an extra oxygen or two to each, it changed the structure quite a bit, but they are still real molecules.

A. CH3CO2-O-CO2CH3

That would be (or at least could be) dimethyldicarbonate:

https://en.wikipedia.org/wiki/Dimethyl_dicarbonate

It would probably work, breaking down into methanol and CO2, but might react with other compounds (see the link). It is used as a beverage preservative (e.g., wine).

B. CH3CO2-O-CH2CH3

This second typo turns out to be ethyl methyl carbonate

http://www.sigmaaldrich.com/catalog/product/aldrich/754935?lang=en&region=US

It is a flammable liquid. It would probably break down in water to ethanol, methanol and CO2.

Happy Reefing. :)
 

toaster77

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A and B are now more comprehensible as possible carbon sources!

While propane would be ineffective, methanol at high enough concentrations might be toxic to certain reef inhabitants. I did a brief search and found a reference claiming that prolonged exposure to ~50 mg/L methanol resulted in reduced growth and fecundity of certain fish species: http://www.ncbi.nlm.nih.gov/pubmed/15162848
 
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Randy Holmes-Farley

Randy Holmes-Farley

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A and B are now more comprehensible as possible carbon sources!

While propane would be ineffective, methanol at high enough concentrations might be toxic to certain reef inhabitants. I did a brief search and found a reference claiming that prolonged exposure to ~50 mg/L methanol resulted in reduced growth and fecundity of certain fish species: http://www.ncbi.nlm.nih.gov/pubmed/15162848

Interesting. Thanks. :)
 

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