Talk:Polycyclic aromatic hydrocarbon

I disagree. The material should be made consistent, but this should stand as a separate, more detailed article as per Wikipedia:Summary style. - Taxman ^Talk 14:36, July 30, 2005 (UTC)

PAH definition conflict

The Polycyclic aromatic hydrocarbon is clear in defining that PAH have no hetero atoms and no substituents. NIST's database seems to agree, as it contains only pure H and C compounds, though their information doesn't seem to include an explicit definition. Here's another definition that agrees with that. However, aromatic hydrocarbon and Category:Polycyclic aromatic hydrocarbons have a looser definition allowing hetero atoms.

Is one definition more correct than the other? And if the definition of a PAH is the strict one, what is a compound that is aromatic and polycyclic, but has hetero atoms and functional groups called? I'm out of my league with regards to chemical knowledge here, and I don't have any authoritative sources to look it up in at the moment. But it is definitely a conflict among our articles that should be fixed. - Taxman ^Talk 14:34, July 30, 2005 (UTC)

Method of carcinogenity

I assume that PAHs are carcinogenic/mutagenic due to their ablility to intercalate DNA. If anyone can confirm a reason for the health effects, it might be good to include it in the article.--24.16.148.75 04:17, 9 July 2006 (UTC)

PAH can definitely contain heteroatoms or substituents

(PAHs) are chemical compounds that consist of fused aromatic rings and CAN contain heteroatoms or carry substituents.

Example: As we begin to produce Ultra Low Sulfur Diesel (less than 15 ppm) in the Americas some of the most difficult to remove sulfur is contained in 4-6 Dimethyl Dibenzothiophene (4-6 DM DBT) or 4-6 DE DBT. These are both substituted and heteroatom containing PAHs. Alkyl substitued PAHs are thought to be more toxic than non-substitued PAHs ref: http://www.uoguelph.ca/cntc/publicat/science_briefs/2003-09-September-CNTC-Science-Brief.pdf —The preceding unsigned comment was added by 208.251.40.100 (talk • contribs) .

If the substituent is an alkyl group, it's still a hydrocarbon. I don't see why molecules that contain elements other than hydrogen and carbon should be called hydrocarbons. —Keenan Pepper 22:41, 12 August 2006 (UTC)

PAH nomenclature and more

Having just looked at this discussion, although I have edited the PAH entry and those of some specific compounds, I will give answers and opinions about the various topics. First, the International Union for Pure and Appied Chemistry (IUPAC) nomenclature rules define a polycyclic aromatic hydrocarbon as the core ring structure only. Heteroatom-containing analogues are called polycyclic aromatic compounds, PACs. The "s" is small case for PAHs and PACs according to the guidelines for publication by the American Chemical Society. These are collective plural categories. PAH refers to one compound or is the adjective form, as in a "PAH spectrum". Polycyclic also, according to the IUPAC rules, refers to those of three or more rings, so naphtrhalene is not formally a PAH. An alkyl-substituted PAH is just that, a category in itself, just like a chlorinated PAH. Although an alkyl substituted PAH is a hydrocarbon, it is not formally a PAH. It is an alkyl-substituted PAH since PAH refers only to the multi-ring, fused aromatic core.

The sulfur PACs are commonly abbreviated as S-PACs, so dibenzothiophene - which is one of the compound types in low-sulfur fuels is a S-PAC and not a PAH.

A few minor comments about PAH nomenclature relating to the letters and numbers in the {}. First, they are braces or the square-cornered brackets, not parentheses. Second, numbers are separated by commas - like 1,2,3,4 or 9,10. Letters are not separated by commas if they are refering to continuous faces of the same fused group - like abcd or pqr. If the faces are not contiguous, as in naming two benzo groups on the same core, there are commas separating each group - like a,h or cd,lm.

AS far as mutagenicity/ carcinogenicity (I will use mutagenicity from now on since carcinogenicity is just mutagenicity in a replicated version - a change in the DNA that can be repeated), it is very dependent on structure. The PAH is not itself mutagenic. It is the oxygen-containing metabolites or oxidation products (hydroxyl, epoxide, ketones, etc.) that actually fit into the DNA structure (an adduct) that cause mutation. This lock and key fitting is what determines mutagenicity. Certain shapes in a PAH become the oxygen derivative that binds to the DNA. So substituents may increase the potency, or not. The key is the fit of the oxygenated derivatives into DNA, the intercolation that leads to replicating mutations. The most potent PAH known, so far, is the unsubstituted dibenzo[def,p]chrysene (dibenzo[a,l]pyrene), which is around 2000 times more active than benzo[a]pyrene in an Ames test.

So isomers can differ greatly in mutagenic activity becausae of shape differences. Alkylation generally reduces mutagenicity because the alkyl substituent both changes the shape of the PAH structure and may occupy the active site which prevents the oxygen derivative formation. Additionally longer alkyl groups, C4 or greater, shield the molecule more from oxidation and make it more lipophilic/ hydrophobic, which means less gets into the aqueous environment for metabolism.

Although the NIST database is thorough and well done, it carries no official significance, other than it is a source of structures and information. The authors, Lane Sander and Stephen wise, say so in the preface. The nomenclature is their best attempt at sticking to IUPAC rules. This is also the stance of Chemical Abstracts - they try, but know they are imperfect. You can find differences in naming the same structure between these two, in fact.

If this information needs to be added to the article, I can provide more references. I added my book on PAHs as a reference and it has much about these nomenclature and biological activity topics.

—fetz the chemist

PAH definition conflict

I added a link to Professor G. P. Moss's IUPAC nomenclature page. He is on the committee for organic chemistry nomenclature. I do not know how to cite this link in the text, so I noted it as being from G. P. Moss.

Also I changed back someone's edit that naphthalene is a polycyclic and clarified. It is a two-ring aromatic hydrocarbon. IUPAC uses "polycyclic" to refer to three or more rings.

—fetz the chemist

Illustrations for the PAH article

I have many illustrations relating to PAHs, especially ones that can be examples of the UV and fluorescence differences among PAH isomers. I also have a few on some of the routes of formation of PAHs. These are ones from my own research work and I can post them here since I have copyright to them. My question is how many of these can I add - along with accompanying text? I will need to learn the way to insert illustrations, but I have them all in electronic form already.

Fetz the chemist

Does not mention PAHs from over-cooked meat from BBQs etc

Must be more deadly if they are actually in your body after eating them. 80.0.116.162 (talk) 22:21, 10 January 2008 (UTC)

Formation of Polycyclic Aromatic Hydrocarbons

The National Academy of Sciences published a paper in 2002 proving that polycyclic aromatic hydrocarbons require pressures greater than 30 kilobar for their formation which corresponds to a depth of 100 kilometers deep in the earths crust. No biological molecule can survive at such a depth because it is past the critical temperature of water.

Of course, this will never be allowed in this article because the fascists who edit wikipedia subscribe to medieval theories.Wikkidd (talk) 20:34, 6 July 2008 (UTC)