Sciencemadness Discussion Board

Border between inorganic and organic chemistry ?

metalresearcher - 6-9-2021 at 02:52

The largest online chemistry textbook states that organic is:
Quote:

The range of chemicals studied in organic chemistry includes hydrocarbons (compounds containing only carbon and hydrogen) as well as compounds based on carbon, but also containing other elements, especially oxygen, nitrogen, sulfur, phosphorus (included in many biochemicals) and the halogens.


So CO, CO2 and water are clearly inorganic as the first two don't contain hydrogen and water does not contain carbon.
But what about H2CO3 which can also be described as COOH.OH.
And soaps (sodium salts of fattic acids) ?

unionised - 6-9-2021 at 03:14

There is no clear distinction.
If you have a carbon-carbon bond it is almost always classes as organic.
The same goes for a carbon-hydrogen bond.
But it's messy.

woelen - 6-9-2021 at 04:32

Just to demonstrate how ill-defined the distinction between organic and inorganic is, the following:
- Experiments with acetato-complexes of transition metals. I have played around with quite a few acetato-complexes (such as the nice red iron(III) complex, the green/blue copper(II) complex). I consider this inorganic chemistry, but acetic acid is considered an organic acid.
- Making tin(IV) iodide in a solution of dichloromethane. Here, I use a solvent, which is considered organic (actually, it also works with CHCl3 and also with CS2), but the reaction is considered inorganic. And is CS2 an organic solvent or an inorganic solvent?

These two examples show that the classification is not hard, there is a certain grey area.

Herr Haber - 6-9-2021 at 06:42

The distinction is clear. I just dont like it from time to time.

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

"For historical reasons discussed , a few types of carbon-containing compounds, such as carbides, carbonates (excluding carbonate esters), simple oxides of carbon (for example, CO and CO2), and cyanides are considered inorganic. Different forms (allotropes) of pure carbon, such as diamond, graphite, fullerenes, and carbon nanotubes[4] are also excluded because they are simple substances composed of only a single element and therefore are not generally considered to be chemical compounds."

The same definition appears almost word for word in a EU Directive from 1999. If the law says so...

Oxy - 6-9-2021 at 10:52
Quote:

The range of chemicals studied in organic chemistry includes hydrocarbons
So CO, [...] are clearly inorganic as the first two don't contain hydrogen and water does not contain carbon



The border is very delicate.
CO can be considered as formic acid anhydride, HCN can be considered as the first of nitrile homologue chain - nitrile of formic acid.


[Edited on 6-9-2021 by Oxy]

Fulmen - 6-9-2021 at 11:24

It's not delicate, it's arbitrary. The only real answer is that it depends on the definition.

DraconicAcid - 6-9-2021 at 11:26

And it's arbitrary because nature does not create categories- we categorize things.

Tsjerk - 6-9-2021 at 11:45

Does it really matter? Cyanide and azide ions are inorganic, but they exist as organic functional groups, and definitely interact with organic molecules. CO2 is inorganic, but most of the time it is created by organic reactions. Organic chemistry (almost) couldn't exist without inorganic chemistry. Chemistry is chemistry and while doing organic, you will see inorganic, and when doing inorganic you will miss a lot when you refuse to look at anything organic.

unionised - 6-9-2021 at 12:33

Quote: Originally posted by Herr Haber  
The distinction is clear. ...
simple oxides of carbon (for example, CO and CO2), ...

What about carbon suboxide and mellitic anhydride?
The last one looks a lot like a benzene derivative.
Or this stuff?
https://en.wikipedia.org/wiki/Hexahydroxybenzene_trisoxalate

Looks pretty organic to me.

On the other hand, things with no carbon hydrogen bond and no carbon carbon bond are often considered inorganic, but urea- which has neither- is arguably the "prototype" organic compound.
https://en.wikipedia.org/wiki/W%C3%B6hler_synthesis
Quote: Originally posted by Tsjerk  
Does it really matter?

No.

[Edited on 6-9-21 by unionised]

DraconicAcid - 6-9-2021 at 12:44

Quote: Originally posted by unionised  

What about carbon suboxide and mellitic anhydride?
The last one looks a lot like a benzene derivative.
Or this stuff?
https://en.wikipedia.org/wiki/Hexahydroxybenzene_trisoxalate


They have carbon-carbon bonds, so I put them in the organic category.

Tsjerk - 6-9-2021 at 13:08

But then what about graphite and diamond? Or does the fact it has oxygen matter?

DraconicAcid - 6-9-2021 at 13:23

Quote: Originally posted by Tsjerk  
But then what about graphite and diamond? Or does the fact it has oxygen matter?


They're not organic compounds, because they aren't compounds.

Tsjerk - 6-9-2021 at 13:36

They are compounds because they have a single molecular structure. Otherwise polyethylene also wouldn't be a compound.

But okay, graphene then?

[Edited on 6-9-2021 by Tsjerk]

CharlieA - 6-9-2021 at 14:09

So hydrogen gas is a compound because it has a single molecular structure? It seems to me that this thread has devolved into splitting hairs. Whether inorganic or organic, it is all chemistry. The division of compounds into inorganic or organic is a centuries-old classification developed when the theory was that organic compounds were only produced by living organisms. Woehler's synthesis of urea (an organic compound) from ammonium cyanate (an inorganic compound) proved that theory to be wrong.

Tsjerk - 6-9-2021 at 14:14

Exactly, it doesn't really matter.

DraconicAcid - 6-9-2021 at 14:42

Quote: Originally posted by Tsjerk  
They are compounds because they have a single molecular structure. Otherwise polyethylene also wouldn't be a compound.

But okay, graphene then?

[Edited on 6-9-2021 by Tsjerk]


No, diamond and graphite aren't compounds- they are form of the element. They only contain one kind of atom.

Texium - 6-9-2021 at 17:12

We may not be able to agree where to draw a line between organic and inorganic compounds, but I think the line between organic and inorganic chemistry is a little more clear. Exchange of ligands around a metal? Inorganic, even if organic ligands are involved, because you're manipulating what is coordinated to the metal, and not making or breaking bonds within the organic molecules involved. Running a clearly inorganic reaction in an organic solvent that doesn't participate (e.g. woelen's tin(IV) iodide example, or when I made phosphorus tribromide in chloroform)? Also inorganic. Running an organic reaction that requires an inorganic acid or base, such as making or cleaving an ester? Organic.

The example that unionised posted about hexahydroxybenzene trisoxalate is an interesting example. While there can be disagreement over whether the product should be considered organic or inorganic, the chemistry used to make it is comfortably in the realm of organic chemistry, because they produce it from hexahydroxybenzene and oxalyl chloride. Nobody would categorize that reaction as inorganic chemistry.

Something that really gets into the gray area is when you have an organic reaction that requires catalysis by a transition metal, because then you have ligand exchange and metal redox happening simultaneously with the organic reaction. But that's why we have a third category: organometallic. :)

[Edited on 9-7-2021 by Texium]

woelen - 7-9-2021 at 00:19

Quote: Originally posted by DraconicAcid  

No, diamond and graphite aren't compounds- they are form of the element. They only contain one kind of atom.
That is one possible definition (e.g. the one on Wikipedia), but I have seen others. Even the noble gases sometimes are considered compounds. They are made of molecules, each consisting of a single atom.

Another definition I have seen:
-----------------------------------
- Elements are the type of atoms. Only appr. 80 elements exist in Nature (not regarding isotopes).
- Compounds are physical substances, made from these elements. Pure metals also are considered compounds, having metal bonds, but they only contain a single element. Noble gases are considered molecular compounds, consisting of very simple molecules, which only contain one atom. Different allotropes of elements are considered different compounds. E.g. O2 and O3 are different compounds.

But it does not really matter how the word 'compound' is defined. What does matter is that you have an understanding of type of bonds, structure of substances, etc.

j_sum1 - 7-9-2021 at 03:05

Quote: Originally posted by woelen  
Quote: Originally posted by DraconicAcid  

No, diamond and graphite aren't compounds- they are form of the element. They only contain one kind of atom.
That is one possible definition (e.g. the one on Wikipedia), but I have seen others. Even the noble gases sometimes are considered compounds. They are made of molecules, each consisting of a single atom.

Another definition I have seen:
-----------------------------------
- Elements are the type of atoms. Only appr. 80 elements exist in Nature (not regarding isotopes).
- Compounds are physical substances, made from these elements. Pure metals also are considered compounds, having metal bonds, but they only contain a single element. Noble gases are considered molecular compounds, consisting of very simple molecules, which only contain one atom. Different allotropes of elements are considered different compounds. E.g. O2 and O3 are different compounds.

But it does not really matter how the word 'compound' is defined. What does matter is that you have an understanding of type of bonds, structure of substances, etc.

I really like that definition. That approach makes so much sense.
Problem is that my students will fail if I teach them that.
(It's like the triangle of power for exponents, powers, and logarithms.)

DraconicAcid - 7-9-2021 at 07:20

Quote: Originally posted by woelen  

- Compounds are physical substances, made from these elements. Pure metals also are considered compounds, having metal bonds, but they only contain a single element. Noble gases are considered molecular compounds, consisting of very simple molecules, which only contain one atom. Different allotropes of elements are considered different compounds. E.g. O2 and O3 are different compounds.


I can't imagine any actual chemist declaring a single atom to be a molecule, or a single element to be a compound. Not one with a first language of English anyway.

chemister2015 - 7-9-2021 at 07:46

I have created 14 rules for my database for dividing substances into organic, inorganic and elementoorganic.

[Edited on 7-9-2021 by chemister2015]

Tsjerk - 7-9-2021 at 10:43

Quote: Originally posted by DraconicAcid  

I can't imagine any actual chemist declaring a single atom to be a molecule, or a single element to be a compound. Not one with a first language of English anyway.


All chemistry is, is a bunch of electron clouds interacting. Those electron clouds and the bonds they form really don't care whether what they are holding together are atoms, molecules or complete visible by light miscroscopy multiprotein bodies like ribosomes for example.

When an element reacts chemically it does so exactly like a compound composed of more than one element, so why not just call it a compound? When it looks like a compound, acts like a compound, it must be a compound right?

Calling helium a molecule might sound strange, but when it reacts the rules it follows are exactly like those for any other molecule.

If you need classifications to understand how things work that is fine, but you really don't have to. And you really don't need English as a first language to grasp a concept.

macckone - 8-9-2021 at 07:10

I use this definition, If the chemistry is manipulating carbon-carbon bonds then it is clearly organic (pure carbon compounds not really manipulating the bonds), if the chemistry does not involve bonds with carbon then it is clearly inorganic. So if you are making a metal acetate, no carbon bonds are effected, it is inorganic.
The edge cases then resolve to non-carbon-carbon bonds which usually are organic.
Exceptions would be things like burning carbon in whatever form or combining carbon monoxide with nickel.