Why are Organic Substances so Often Brown ?

[wwswimming]

leaves that haven fallen off a tree
earthworm castings
chocolate

i'm sure we could all name a few more.
perhaps it's more instructive to concentrate
on one material in detail.

so, to keep it what my mother would call
dinner table conversation, i will pose the
question, why are the leaves that fall off
the tree, brown ?

from limited experience, i've gotten gold
by using an RGB value of 222 - 188 - 133,
which is too bright for brown.

so, brown might be, 111, 88, 44, those
red-green-blue values would be brown.

i could theorize that the leaves have chlorophyll
in them, so that contributes some green.

but what are the chemicals that add red and
blue to the color of the dead leaf ?

and why does chocolate have a similar color,
though darker ?

 

[CycloWizard]

Color isn't necessarily generated in your eye the way you are thinking it is. There is some overlap in the absorption wavelengths of the three photoreceptive molecules. We nominally say that they absorb red, green, or blue, but this is really a simplification and they each have an absorption spectrum that is fairly broad. Apart from that, I'm not sure I can answer your first question because I know virtually nothing about plant biology.

I would also like to add that I don't see a great prevalence of brown in organic systems. My lab specializes in making transparent polymers using organics. However, pigments made from organics are used in paints to make virtually every imaginable color.

Finally, you would do well to remove the link to lasiksos from your sig. LASIK is one of the safest surgeries on the planet. I've not had it only because I can't afford it (grad student stipends aren't exactly high enough to support elective surgeries ), but otherwise I certainly would and I work in an ophthalmology department. I'm well acquainted with the risks and they are few and far between. But I digress.

 

[firewolfsm]

the chlorophyll stops being produced when the leaves fall off (obviously) so there's no green. You don't get color in substances by mixing colors, the light bounces off at certain wave lengths and we interpret that as color. It's because of the molecular structure.

 

[Deathonastick]

actually, most organic substances are pinkish to red in color.

 

[firewolfsm]

and lasik is very safe.

 

[Howard]

What about hydrocarbons?

 

[dkozloski]

You spend too much time staring in the toilet bowl.

 

[wwswimming]

Originally posted by: CycloWizardFinally, you would do well to remove the link to lasiksos from your sig.

CycloWizard, how is it that i "would do well to remove the link to lasiksos" from my Sig ?

Please explain.

 

[firewolfsm]

He did explain.

 

[taltamir]

few and far between risks does not equate to safe... neither does "safest surgery"... lasik might very well be the safest surgery on the planet... but surgery complications could normally kill you, in lasik they just result in chronic eye pain and seeing impairment in a worst case scenario... still not an outcome I would risk for a chance to not need glasses.

 

[Nathelion]

Originally posted by: taltamir
few and far between risks does not equate to safe... neither does "safest surgery"... lasik might very well be the safest surgery on the planet... but surgery complications could normally kill you, in lasik they just result in chronic eye pain and seeing impairment in a worst case scenario... still not an outcome I would risk for a chance to not need glasses.

I would take that rather small risk... what I have more of a problem with is the reduction in field of view.

 

[CycloWizard]

Originally posted by: taltamir
few and far between risks does not equate to safe... neither does "safest surgery"... lasik might very well be the safest surgery on the planet... but surgery complications could normally kill you, in lasik they just result in chronic eye pain and seeing impairment in a worst case scenario... still not an outcome I would risk for a chance to not need glasses.

That's your choice. But the site he has linked to is nothing but a scare site designed to make the risks out to be much greater than they are, and I do take exception to that. I have met the guy who invented LASIK and he's still wearing glasses, but that wouldn't dissuade me from getting it, either. Hell, I'm even working on something to replace LASIK and I still don't think it's a bad idea. People should choose whatever they want given that they are well informed, as is required by law. Trying to scare people away by spreading exaggeration and half-truths is nonsense though.

 

[wwswimming]

But the site he has linked to is nothing but a scare site designed to make the risks out to be much greater than they are.

wrong. that website is understated. though it does present
a little too much information at once, from a technical writing
point of view.

if you see any factual errors, one factual error, on any of the
LASIK websites that i put in my sig, please let me know.

 

[CycloWizard]

Originally posted by: wwswimming
wrong. that website is understated. though it does present
a little too much information at once, from a technical writing
point of view.

if you see any factual errors, one factual error, on any of the
LASIK websites that i put in my sig, please let me know.

Here's a factual error... Took me about 15 seconds to find.

Now, it appears, LASIK itself is getting a bad name, and so the refractive surgeons are changing the name, marketing "LASEK" and "all-laser LASIK".

LASIK is not the same thing as LASEK or "all-laser LASIK," which is actually called "bladeless LASIK" in every publication I've ever read. And no, the website is not understated, nor is its interest true "informed consent." It offers purely anecdotal evidence about 95% of the cases it describes with absolutely no evidence. If these people did not receive true informed consent, then they should be suing the crap out of these doctors for malpractice. If, instead, they were informed of the potential complications (which I can almost guarantee that they were, since that's the law), then they have little room to complain. Bottom line: it's an elective surgery with a very low chance of complications, all of which are pretty well known at this point. If you choose to have the surgery knowing the risks and something goes wrong, it's not the doctor's fault - you took the chance. The same is true of any elective (or even non-elective) surgery.

edit: I will also add the following after another brief skimming of one page on the site:

Unfortunately, the plot thickens. The patient with the metal dust embedded in their cornea, and the constant eye-pain, participated in a clinical trial when they had their LASIK. That clinical trial was conducted in conjunction with a local university. When we called that university to request a copy of the record of that patient's participation in that clinical trial, we were told that there was NO RECORD of that patient's participation in that clinical trial.

In my opinion, Doctor Tooma deliberately removed the record of that patient's negative outcome from the clinical trial.

This is pure ignorance. HIPAA laws do not allow such disclosures. In fact, if the university had disclosed that someone by that name had been involved in a clinical trial, much less given someone the related records, they would have been fined and perhaps even barred from conducting any clinical exams and/or trials indefinitely. Physicians cannot even tell you if someone you know is a patient of theirs, much less whether they performed a specific procedure on said person, because of privacy laws. In many cases, you will not even be informed if a loved one is undergoing an emergency procedure in the hospital because the hospital's disclosure of that information to you is a violation of privacy law. I think that these laws suck for many reasons, but I do know that they are the law as of the late 1990's.

 

[Cattlegod]

i had lasik and it is the best that that has ever happened to me.

 

[PolymerTim]

On the original topic:

I don't know a lot about color, but I am a bit of a chemist so I can talk a little about my experience with color in organic systems. In pure form, most liquid organics are near colorless (think of gasoline, ethanol, paint thinner). If you've ever seen movies and pictures of chemistry labs with brightly colored liquids, they are usually adding food coloring to water for the picture. I have a solvent cabinet with more than 20 different solvents and they all range from colorless to pale yellow.

Now thats for pure liquids only. When you start dissolving things into those liquids the story changes a bit since you're now seeing a diluted version of the solute's color. Solutions can vary widely in color and many are brown. In my chemistry with small molecules, most of the time I see any brown, it is actually an impurity and not my desired product (not always). Similar to getting sugar from molasses, purification removes the color.

I wish I knew more about why, Ive never really investigated the subject. But it does seem that only a small amount of a colored substance dissolved in a solution can bring a substantial amount of color. And I wonder whether brown is really the effect of a single chromophore, or just a blending of multiple colors. Personally, whenever I mix my watercolors, I always get brown. Last time I checked the rainbow of colors, brown wasn't in them, so I assume it requires a mixture of colors and is not a pure color itself.

-Tim

 

[MrPickins]

If you're talking about decomposing organic matter, I'd guess it's just because you have a mixture with a wide range of colors blending together. Usually you'll end up with a brown or muddy green doing that with pigments.

 

[Throckmorton]

Brown is just a dull/dark orange, so it is a part of the rainbow.

 

[sao123]

90% of all possible substances created from our periodic table are white in color.

 

[Slammy1]

I'm sure it's related to the reactivity of oxygen with organic chemicals producing unsaturation. For example, consider alcohols:
http://www.chemguide.co.uk/org...lcohols/oxidation.html

Some basic absorbance theory:
http://www.chemguide.co.uk/org...lcohols/oxidation.html

The introduction of unsaturation to the organic compound produces pi orbital electrons which absorb at characteristic wavelengths. Most pure chemicals do not absorb in the visible region, typical organic analysis is in the UV range for quantitation or radio/IR for ID. This is a spectroscopist point of view, I'm sure if you asked a physicist you'd get a different answer.

 

[wwswimming]

wow, the thread is back on topic !

 

[gururu2]

things appear black because they absorb the complete visible range. less black is equivalent to brown, indicating that much of the visible spectrum is being absorbed, albeit not completely. very few molecules aside from dyes and tannins have the capacity to absorb so many different wavelengths. typically it requires a large mix of molecules containing chromophores http://en.wikipedia.org/wiki/Chromophore. a good example is crude oil, which contains hundreds of compounds that suck all the color out of light.

 

[PolymerTim]

I remembered what causes a lot of the brown colors in my chemical reactions. I sometimes use amines or amino compounds and they have a tendency to turn very brown as they age. The amines themselves are usually very light in color, but are not very stable and many of their byproducts become brown.

So I did a quick google search for "brown amine compound color" and stumbled across some interesting sites. As I expected, this is a common source of brown colors in nature, but I didn't realize it was why my bread crust turned brown!

http://www.the-scientist.com/news/print/53865/

The link above is a chemistry of cooking type article (I love those) and I think is a pretty interesting read. It gives two very common sources of brown color. The first, known as a Maillard reaction, is seen most often in cooking when amines from broken proteins, sugars, and high heat come together to produce some nice dark colors and fragrances (such as in pan-seared meats). The second scenario, I think is a good candidate for why leaves turn brown, although it is used to describe what happens when you overcook your vegetables. Apparently in an acidic environment, chlorophyll is converted to pheophytins which tend to look murky brown.

http://www.freshpatents.com/Br...105ptan20060003061.php

Along those lines, I also found an interesting patent on a new type of browning agent for microwaveable dishes. It basically is looking at that same Maillard reaction, but lists a lot of very specific examples of its use in the food industry today. I think this is a great read to showcase just how much research goes into foods today. Can you imagine a whole team of scientists trying to make a microwaveable pizza that turns brown and crispy in the microwave just like it does in the conventional oven? If you can't imagine that, just imagine how much money a company would make that could bring that to market without similar competition.

Hmm, maybe I should start a thread on food science. I really love that topic.

-Tim