Reef Chemistry Question of the Day #183 A Supersaturated Organic Molecule in the Ocean

[Randy Holmes-Farley]

Reef Chemistry Question of the Day [HASHTAG]#183[/HASHTAG]

I ran across an interesting fact today that I had never heard before when reading a section of a book to try to answer a complex question in this forum. So I'll use it as the question for today. I don't expect most readers will already know this fact, but astute ones may be able to deduce it from their knowledge of chemistry (or by guessing ).

Which organic molecule is supersaturated in the surface layers of much of the ocean?

Supersaturation means there is more of it present that would be present if the system was allowed to come to equilibrium. So, for example, it might precipitate as a solid or disappear into the gas phase if it was not being replaced somehow faster than this could naturally happen.

Choices are...

A. Ethanol
B. Acetate
C. Dimethyl sulfide
D. Methane sulfonate

Good luck and let us know your reasoning!




























.

 

[JimWelsh]

I'll give my answer and reasoning cryptically, but Randy should understand: Pilson, page 289.

 

[jason2459]

Will have to look this up but my answer to part of this question on supersaturation just under the surface of the water would be Oxygen due to the high amount of photosynthesis.

Edit: And looking at the answers and thinking about it because of the oxygen production I'll say Dimethyl sulfide would be up there as well from the same source that produced the oxygen.

 

[aaron23]

c or d. my guess i would like to use a lifeline

 

[jason2459]

methane is abundant for sure and consumed quite a bit

 

[KWSanders]

certainly not A who would waste ethanol in the ocean while on vascation???

 

[Cory]

Methane id say

 

[s2nhle]

I would say D without opening my chemistry book.

 

[Randy Holmes-Farley]

And the answer is...C. Dimethyl sulfide

Bacteria make a lot of dimethyl sulfide in the ocean. There is a big plante-wide cycle of sulfur throught eh ocean and atmosphere,a nd dimethyl sulfide is a big player.

First, dimethylsulfide (DMS) looks like this: CH3-S-CH3. It is pretty nonpolar and not very soluble in water, so it can easily become supersaturated in seawater.

The first part of the cycle starts with marine algae make a different molecule, dimethylsulfonium proprionate (DMSP) from the amino acid methionine. It is charged and they use it for osmotic regulation. Bacteria then get ahold of the DMSP and convert it into DMS plus another organic molecule.

Here's a web site with more on DMS and the sulfur cycle:

http://ocw.mit.edu/courses/earth-at...stry-of-sulfur-fall-2007/projects/clayton.pdf

As to the other possible choices, all of them would be very soluble in seawater, and none are close to being "saturated".

 

[s2nhle]

Wow, learn something new. Thank you. I should go back to college and take some more chemistry class. LOL.

 

[Randy Holmes-Farley]

Wow, learn something new. Thank you. I should go back to college and take some more chemistry class. LOL.

You're welcome.

Glad it was interesting.

 

[jason2459]

Wow, learn something new. Thank you. I should go back to college and take some more chemistry class. LOL.

I remembered that one from some marine biology courses in South Florida. Had to brush off the cob webs in the brain though for that. It's been a while. They were a lot of fun and I highly recommend it. You can sit courses for very cheap or you used to be able to.