Talk:Polycyclic aromatic hydrocarbon

Untitled

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)

UV-FL Spectra

Does anyone know where to find the UV-vis and fluorescence spectra online? These would be very useful. —Preceding unsigned comment added by 74.247.199.50 (talk) 20:26, 12 July 2010 (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)

Polycyclic aromatic hydrocarbon are hydrocarbons. Hence, they consist of carbon and hydrogen only. --Itub (talk) 12:35, 9 November 2008 (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)

PAHs are metabolized into a variety of derivative, mostly oxygen-containing ones like hydroxyl, keto, and endo-epoxide versions. These then fit into and bind to DNA, foeming adducts. These change the cell replication.

By the way, the article mentions benzo[a]pyrene as the first known chemical carcinogen. In looking at references, I think that there are differences. Bpa]P was the first from coal-tar isolated fractions. The first from a pure, organically synthesized compound was dibenz[a,h]anthracene. Fetz the chemist —Preceding unsigned comment added by Fetz the chemist (talk • contribs) 15:46, 7 November 2008 (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

Worth inclusion

The information on nomenclature belongs in an article on nomenclature, rather than here. This article on PAHs should link to the IUPAC nomenclature of organic chemistry article, and your (Fetz) information could improve that article. Of course, this article should use compliant names -- see Wikipedia:Naming conventions (chemistry).

The mutagenicity information is noteworthy, hence well worth including in this article, always assuming it complies with Wikipedia policies e.g. WP:OR.

yoyo (talk) 18:41, 25 May 2010 (UTC)

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

I consulted the 1998 nomenclature recommendations paper by Moss but find no statement about "polycyclic" referring only to compounds three or more rings. There doesn't seem to be a formal definition of the category called "polycyclic," just guidelines for naming given structures. In part of Reference 3, as cited by the Moss 1998 document, two ring compounds are explicitly labeled "polycyclic." Could you clarify?

Fkaser (talk) 23:17, 28 July 2008 (UTC)

I asked Professor Moss, and naphthalene is a bicyclic. The categories are monocyclic, bicyclic, and polycyclic for all ring systems of any type.

Fetz the chemist —Preceding unsigned comment added by 4.243.164.4 (talk) 21:00, 7 November 2008 (UTC)

Do PAHs include naphthalene? Neither CAS nor IUPAC defines "polycyclic aromatic hydrocarbon" in the nomenclature publications that I have consulted:

IUPAC 1993 recommendations for organic compounds

IUPAC 1998 recommendations for fused ring systems

IUPAC draft 2004 recommendations for organic compounds

Chemical Abstracts (CAS) 2002 naming instructions

IUPAC Compendium of Chemical Terminology - the Gold Book

Also, IUPAC does not define the suffix poly- anywhere that I can find. CAS defines poly- as "many" under Paragraph 309, which is not useful in this context. Thus, it's necessary to look at how IUPAC and CAS use the prefix poly- to determine if naphthalene is a PAH.

The IUPAC 1979 recommendations for organic compounds, under Fused Polycyclic Hydrocarbons, Rule A-21, list pentalene, indene, naphthalene, azulene, and heptalene, all bicyclic hydrocarbons. (http://www.acdlabs.com/iupac/nomenclature/79/r79_63.htm)

In the IUPAC 1993 recommendations for organic compounds, Table 20 on page 164 is labeled "Unsaturated polycyclic hydrocarbons" and lists naphthalene, azulene, and indene, all bicyclic hydrocarbons. (http://www.acdlabs.com/iupac/nomenclature/93/r93_687.htm)

The IUPAC 1998 recommendations for fused ring systems, under Rule FR-2.1.4, Polyalene components, list pentalene, heptalene, and octalene, all bicyclic hydrocarbons. http://www.chem.qmul.ac.uk/iupac/fusedring/FR21.html#214

The IUPAC draft 2004 recommendations for organic compounds, Rule P-25.1.2.3, Polyalenes, list naphthalene, pentalene, and octalene, all bicyclic hydrocarbons. [Sorry, no web page for this]

The CAS Naming guidelines (2002) under Paragraph 147 say, "Polycyclic systems may be divided into four classes as follows: (a) Fused systems contain at least two rings of five or more members ..."

IUPAC and CAS are the accepted authorities in the chemistry discipline for chemical names and terms and both of them include bicyclic compounds under various terms that include the suffix poly. Clearly, polycyclic aromatic hydrocarbons include bicyclic aromatic hydrocarbons and naphthalene is a PAH.

Citations:

IUPAC. Nomenclature of Organic Chemistry, Sections A, B, and C. 1979. Edited by J. Rigaudy and S.P. Klesney. http://www.acdlabs.com/iupac/nomenclature/

A Guide to IUPAC Nomenclature of Organic Compounds, Recommendations 1993. Edited by R. Panico, W.H. Powell and J.C. Richer. http://www.acdlabs.com/iupac/nomenclature/

IUPAC. Nomenclature of Fused and Bridged Fused Ring Systems, Recommendations 1998. Prepared for publication by: G.P. Moss. http://www.chem.qmul.ac.uk/iupac/fusedring/

IUPAC Draft 2004 Preferred IUPAC Names. [My copy is a .PDF that does not list authors or editors other than IUPAC and I don't have a web page reference for this although I downloaded the .PDF not too long ago.]

IUPAC. Compendium of Chemical Terminology, "The Gold Book" Second edition, 1997. Edited by A D McNaught and A Wilkinson. Revised web version at http://www.chem.qmul.ac.uk/iupac/bibliog/gold.html

Naming and Indexing of Chemical Substances for Chemical Abstracts. A reprint of Appendix IV (Chemical Substance Index Names) from the Chemical Abstracts 2002 Index Guide. 2002. Chemical Abstracts Service.

Ken the chemist (talk) 22:37, 14 February 2009 (UTC)

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.

http://www.pnas.org/content/99/17/10976.full?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=genesis+of+hydrocarbons+and+the+origin+of+petroleum&searchid=1085470440708_510&stored_search=&FIRSTINDEX=0

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)

Please keep your POV edit warring in the appropriate articles. This is not the place to push abiotic oil. By the way, why don't you understand that just because Kenney and Kutcherov assert something doesn't mean that it has been proven. Enough geologists and chemists have told you so that maybe you should start being agnostic about the idea. NJGW (talk) 17:30, 9 July 2008 (UTC)

If you do detailed molecular analysis of petroleum, you find molecules that are perfect structures of reduced forms of biological molecules such as steroids and porphyrins. The concept that the original peripheral hydroxyl groups get removed is simple, acidic catalysis by something like aluminum oxide at low temperatures of 100 C to 200 C can be done in the lab. Making similar structures from constituent atoms is very thermodynamically improbable because carbon and hydrogen (and nitrogen in the case of the porphyrins) do not self-assemble into large structures.

These calculations assume hydrogen and carbon atoms joining together as aggregate large molecules, which is bot kinetically and thermodynamically unfavored. But any biological process when looked at from those fundamebntal aspects. But plants and aminals do make long hydrocarbon chains in molecules like stearic acid. It's in the blobs of ear wax accumulating in your ears. —Preceding unsigned comment added by Fetz the chemist (talk • contribs) 22:19, 19 July 2008 (UTC)

Polycyclic Aromatic Hydrocarbons

It hasn't been mentioned yet that PAHs are also created by grilling and similiar types of cooking. I've added a mention plus reference to correct this.NJGW (talk) 03:59, 22 September 2008 (UTC)(LOki0115)

Kekulene

Should there be a section in this article on Kekulene? (C48H24) —Preceding unsigned comment added by 205.250.72.175 (talk) 03:49, 22 September 2008 (UTC)

A superbenzene? Sounds cool... what's it do? ;) As long as it's well sourced, not too technical (and hopefully someone has a GFDL picture of the molecule) it could be a good addition. Maybe some day get it's own article. NJGW (talk) 03:59, 22 September 2008 (UTC)

PAH

Considering that naphtalene has only 2 fused rings and if IUPAC said that only compounds with at least 3 fused rings are PAH (as the page says), why did you add naphtalene in the array with names and formulae ? It has no meaning ? I simply need an explanation because it is written that those compounds are PAH... but naphtalene not. —Preceding unsigned comment added by 132.210.213.127 (talk) 20:52, 10 January 2011 (UTC)

Introduction

The introduction should possibly include in the first sentence what an aromatic hydrocarbon is so as to frame the discussion for people who don't necessarily know what that is. (74.198.151.49 (talk) 04:03, 9 February 2011 (UTC))