Talk:IUPAC nomenclature of organic chemistry

IUPAC nomenclature of organic chemistry was a Natural sciences good articles nominee, but did not meet the good article criteria at the time. There may be suggestions below for improving the article. Once these issues have been addressed, the article can be renominated. Editors may also seek a reassessment of the decision if they believe there was a mistake.

Article milestones
Date	Process	Result
May 18, 2011	Good article nominee	Not listed

What does this sentence mean?[edit]

"By suffix, it is meant that the parent functional group should have a suffix, unlike halogen substituents. " Could the person, who added the entry elaborate a little more on what is a 'parent functional group', 'a substituent' etc.? — Preceding unsigned comment added by 156.17.236.5 (talk) 19:55, 4 November 2011 (UTC)[reply]

Numbering, by sum or smallest number?[edit]

Under Basic Principles, it is currently stated under instruction 6.1. that the numbering is done according to which order (right to left or vice versa):

"Has the lowest locant (or sum of locants) for the suffix functional group. Locants are the numbers on the carbons to which the substituent is directly attached."

Later, in the example of 18-bromo-12-butyl-11-chloro-4,8-diethyl-5-hydroxy-15-methoxytricos-6,13-dien-19-yne-3,9-dione, it is stated in instruction 2.2. that:

"The numbering of the molecule is based on the ketone groups. When numbering from left to right, the ketone groups get numbered 3 and 9. When numbering from right to left, the ketone groups get numbered 15 and 21. 3 is less than 15, therefore, the numbering is done left to right, and the ketones are numbered 3 & 9. The lesser number is always used, not the sum of the constituents numbers."

To me this seems contradictory. Could someone please clarify and/or correct? 88.195.173.125 (talk) 21:07, 14 March 2011 (UTC)[reply]

I found the same issue. In the blue book it says "so as to give lowest locants to the following structural features (if present) considered successively in the order listed until a decision is reached." It is not specific whether to give the minimum available value or the lowest sum. I kind of think because it says successively the lowest value is the correct. Hopefully can can find someone who is well versed with IUPAC standards. Youarefunny (talk) 23:48, 2 November 2011 (UTC)[reply]

I have learned that you should name with triple bonds, then double bonds, then functional groups, then alkyls in that precedence order. is that wrong? Ws04 (talk) 01:33, 11 December 2014 (UTC)[reply]

The latest version of the Blue Book states (P14.3.5, p 34):

"The lowest set of locants is defined as the set that, when compared term by term with other locant sets, each cited in order of increasing value, has the lowest term at the first point of difference."

i.e. line up all the numbers in ascending order, compare the lowest numbers of the two possible names, second lowest numbers, etc. until there's a difference. The set of numbers with the lower number at this first point of difference is correct. Labmuffin (talk) 05:48, 26 October 2018 (UTC)[reply]

Amides[edit]

In my opinion there is a little error in the text about Amides. It is stating that Amides are always terminal so there would not be a need for a prefix for them. But looking for example at http://en.wikipedia.org/wiki/Carbamoyl_phosphate you can see that in this case the Amide group is used as a prefix and not as a suffix because of the phosphate group. I do not know why phosphate does take precedence in this case but due to that exception in nomenclature I would recommend changing the statement in the entry about Amides implementing the prefix "Carbamoyl-". Furthermore I guess that the article does not state that the basic form of an Amin is Ammonia(NH3). If you for example have Triethylamine you would have N(CH2,CH3)3. So the three H-atoms of N would be substituted with Ethyl groups! —Preceding unsigned comment added by Xc!te (talk • contribs) 18:02, 30 December 2008 (UTC)[reply]

Does the first letter of the name have to be capitalized?[edit]

Some text books say that it does. Is there a rule stating this?

There is a rule, and it states the opposite! Chemical names are common nouns, and should only be capitalized at the beginning of a sentence (or in a title in U.S. English). Physchim62 (talk) 08:17, 12 October 2006 (UTC)[reply]

Just to add - The names are capitalized in German but that is because all nouns are capitalized in German.130.225.245.182 20:35, 13 November 2006 (UTC)[reply]

1-butene or but-1-ene (infixed numbering system)[edit]

I have been taught that it is 1-butene and after looking at other pages, such as Isomers of butylene, that form is used on wikipedia as well. So is one more correct than the other or are they interchangable and both correct under IUPAC? 70.49.20.43 22:53, 3 March 2006 (UTC)[reply]

I too have been taught in school over the past 4 years that the numbering of suffixes comes before the root and not in the middle (eg 1-butene, 1,2-ethanediol, 2,2-dibromo-1-hexene.) I have only ever seen the root-number-suffix format used in much older textbooks, but I'm far from an expert... Besides, hex-1-ene just sounds goofy :P Bungeh 07:59, 7 March 2006 (UTC)[reply]

While "hex-1-ene" may sound goofy and seem like a useless convention, it places the position information directly with the functionality it is describing: the "1" describes the "ene"; the fact that the unsaturation is at position 1 is unrelated to the fact that it's a six-carbon chain, so why should it be a "1-hex" thing? For multifunctional compounds, localizing the number with what it describes can make a name easier to understand. Calling C=CC#CC "pent-1-en-3-yne" clearly identifies which unsaturation is where on the chain. Otherwise you have something like "1,3-pentenyne", and one's mind has to keep jumping back and forth to keep correspondence between the positional numbers and the unsaturation types. DMacks 17:50, 7 March 2006 (UTC)[reply]

I guess that makes sense, especially when there are multiple suffixes; but like I said, the 1-hex was what I was taught at school. I guess a better question then is why are schools (Australian schools at least) teaching the nomenclature wrong :| Bungeh 04:52, 9 March 2006 (UTC)[reply]

DMacks is perfectly correct, and has probably explained it better than I can! If we take the other common example—2-propanol or propan-2-ol—according to IUPAC grammar, 2-propanol is the alcohol which is derived from 2-propane (which doesn't exist). The name isopropanol is disallowed for the same reason, although isopropyl alcohol (following different grammar) is permitted. Schools often teach the nomenclature wrongly, in a mistaken effort to be "purer than pure": hence ethanoic acid is a perfectly acceptable systematic name, but IUPAC would prefer that you call it acetic acid. For usage on Wikipedia, see Wikipedia:Naming conventions (chemistry). Physchim62 (talk) 17:34, 10 March 2006 (UTC)[reply]

There are two standards of IUPAC naming that are still going around, the 1979 version and the 1993 version. Since most professors and book writers around today probably learned the 1979 version, they still use the old fashioned 1-butene convention instead of but-1-ene. I don't think it's really wrong, so much as archaic (sort of like saying thee and thine). Everyone will still recognize it (and probably still has to if they're reading any chemistry papers before '93) but I think the "correct" version is but-1-ene.

I teach in the US, and the 1-butene, 2-propanol style is standard here in all the textbooks when teaching "IUPAC" names. Very confusing! To say nothing of the tendency in some books (thankfully not Wade, the text I use) to call things like 2-propanone instead of acetone, which only adds to the mix. Maybe we should go back to giving things names like dephlogistated air? Walkerma 21:34, 10 October 2006 (UTC)[reply]

Don't you mean dephlogisticated air? :) Physchim62 (talk) 08:18, 12 October 2006 (UTC)[reply]

Maybe my mangled version will become the new US spelling? :) Walkerma 14:16, 12 October 2006 (UTC)[reply]

Infixed numbering is indeed not taught in textbooks in the USA, regarding IUPAC nomenclature. The convention is to place the number at the beginning of the name (e.g. 2-butene); this applies to other substituents as well (there is no propan-2-one for acetone in US textbooks).

71.241.124.193 (talk) 07:34, 24 November 2007 (UTC)[reply]

I teach from the McMurry text, which states in its 7^th ed (2008):

We should note that the IUPAC changed their naming recomendations in 1993 to place teh locant indicating the position of the double bond immediately before the -ene suffix […] This change has not been widely accepted by the chemical community, however, so we'll stay with the older but more commonly used names.

It then gives examples of both styles for several compounds, but in later areas only uses the older naming style. There is also a statement about the use of infix for ketones as being the newer IUPAC rule, but again, after a few comparison examples, does not appear to use it. DMacks (talk) 19:23, 24 November 2007 (UTC)[reply]

The actual rule is to use but-1-ene, because when naming larger compounds, but-1-ene is the only usable way. ManishEarth^{Talk • Stalk} 03:45, 7 March 2009 (UTC)[reply]

Shouldn't this issue be mentioned in the relevant section of the article? — AlanM1 (talk) 11:53, 15 April 2012 (UTC)[reply]

Halogens missing from functional group precedence chart[edit]

I know halogens need to be on the list. I just don't know where. I've looked through two chemistry books and the IUPAC website, but still can't get a straight answer.

Plz fiz thx!!!1

Halogens do indeed belong on the precedence chart. They take the lowest precedence just above Alkanes (and alkanes don't change the suffix at all.) It should also be noted that Alkyne and Alkenes are missing from the precendence chart as well. They should fall in between Amines and Ethers. This is of course for numbering purposes and for which functional group takes priority for changing the last name and then which gets numbered with the lowest number on the parent chain.

Halogens are no longer considered as functional groups but as side chains, because they are in the form of the prefix in an IUPAC naming. —Preceding unsigned comment added by 110.172.31.52 (talk) 12:58, 30 October 2010 (UTC)[reply]

My notes include this list of priorities: 1. COOH 2. Aldehydes 3. Ketones 4. Alcohols 5. Amine 6. Alkyne 7. Alkene 8. Ether 9. Ether 10. Halogen 11. Alkane Elleacampbell (talk) 16:43, 13 October 2008 (UTC) [reply]

Possible misnaming of 4-(1-methylpropyl)octane[edit]

It appears to me that the compound 4-(1-methylpropyl)octane is misnamed. My reading of this page is that the correct name for that compund is 3-methyl 4-propyloctane (based on rule C-13.11a). Evand 05:40, 14 Aug 2004 (UTC)

You're indeed correct -- the methyl substituent on the supposed "branch" is closer to the end than the "propyl group" (which is erroneously shown as the beginning end), so the "branch" should really be an ending. I'm going to edit the page in a sec to comment out the picture until it can be recreated, and I'll try to come up with a better example for the paragraph immediately below it. I also intend to ping the image's creator in some way, although I'm not yet sure how I'll do so. --Waldo

Propan-2-one is redundant. It should simply be propanone. Why? If there were such a thing named propan-1-one it would be misnamed... that's proponal. Perhaps an organic chemist can drop in an fix what otherwise is a great set of graphics and information. User:sturmde

IUPAC Nomenclature is much broader than you represent[edit]

The scope of IUPAC Nomenclature recommendations is very large and you've barely scratched the surface here. I'd recommend that you consider renaming the article to something that better reflects the scope of information presented, or provide an overview of the entire IUPAC Nomenclature universe. Even the scope within organic chemistry is much broader than what you present here .. see http://www.iupac.org/reports/provisional/abstract04/favre_310305.html. For the full flavor of what IUPAC encompasses see http://www.iupac.org/divisions/index.html. Courtland 02:24, 2005 Mar 8 (UTC)

Why is it 2,2 dimethyl-propane?[edit]

Don't both the methyl groups have to go on the carbon 2? Shouldn't it be dimethyl propane? This just says, take a propane molecule and stick two methyl groups on it...

If you choose carbon 1 or 3 then you lengthen the longest chain. Thus you must stick them both on carbon 2.

Appreciate this may be obviously flawed, I have just started chemistry at school.

Richard

I'm reasonably certain you are correct. It's also called neopentane. Evand 03:13, 15 September 2005 (UTC)[reply]

Yes, my fault I'm afraid. There are a few errors like this in the article mostly due to my bad memory/research. Feel free to change it to, say, 2,2-dimethylbutane and I'll try to update the related image in my copious free time. -- DrBob 19:08, 15 September 2005 (UTC)[reply]

Ok, thanks for your help. Will have a go at fixing it.

Richard

As our article points out, the preferred name for this compund is indeed neopentane. Physchim62 (talk) 18:42, 19 February 2006 (UTC)[reply]

I just checked the 3rd Edition Blue Book (1971) and it says (page 6) "The following names are retained [my italics] for unsubstituted hydrocarbons only... Neopentane". So it was not exactly "preferred". Pointillist (talk) 01:24, 26 March 2008 (UTC)[reply]

The 1993 Recommendations also use the phrase "retained in these IUPAC recommendations for naming organic compounds". In other words, these are the recommended names for such compounds. Physchim62 (talk) 13:48, 26 March 2008 (UTC)[reply]

Point taken - dimethylpropane isn't listed in the online version. I had in mind that "preferred" had a special meaning in IUPAC... oh well. Pointillist (talk) 00:46, 28 March 2008 (UTC)[reply]

Actually so did I—think that the Blue Book used "preferred" with some special meaning—until I checked my sources! Nevertheless, I don't think there's any harm done in using the term on WP. Chemical nomenclature is complicated, and we all make mistakes from time to time! Physchim62 (talk) 16:42, 28 March 2008 (UTC)[reply]

Actually, neopentane is a trivial (common) name. Dimethylpropane is correct.ManishEarth^{Talk • Stalk} 03:48, 7 March 2009 (UTC)[reply]

sugars[edit]

where do they fit in the nomenclature?

The nomenclature of sugars is separate from that of other organic compounds: the detailed recommendations can be found here. Physchim62 (talk) 18:42, 19 February 2006 (UTC)[reply]

Is CH₃F₃N⁺ trifluoromethylammonium?[edit]

Could you not argue that (CF₃)NH₃⁺ is trifluoromethylammonium, as well as (CH₃)NF₃⁺? How would you distingiush them? Would you have to say the (CF₃)NH₃⁺ is trifluoromethyltrihydridoammonium?

(CF₃)NH₃⁺ would be trifluoromethylammonium. (CH₃)NF₃⁺ could be uniquely named N,N,N-trifluoromethylammonium, whith the N denoting substitution on the nitrogen, rather then on the carbon (Not to be confused with the lower case n used to denote straight chain alkanes). This systematic name may not be correct by the current IUPAC naming method however.

Parentheses can help here, as in (N,N,N-trifluoro)methylammonium vs. (trifluoromethyl)ammonium. Same disclaimer as the previous editor, my knowledge of these obscure details is a bit hazy. Walkerma 05:48, 3 October 2006 (UTC)[reply]

IUPAC doesn't give unique names, and has never pretended to! The two possibilities suggested by Walkerma seem pretty unambiguous to me: however the first species does't seem to exist, which simplifies naming matters considerably: I would not be confused by the name even in the absence of parentheses. Physchim62 (talk) 14:34, 5 October 2006 (UTC)[reply]

IUPAC vs CAS[edit]

There seems to be a page for registry numbers, but none for CA nomenclature or for chemical nomenclature in general. Since there seems to be difficulty getting even one of these finished, shouldwe consider combining them? i must first admit that though I'm very willing to set up pages, I am not quite so responsible about filling them in,especially here, where I would constantly have to check everything. I was a chem librarian once, but that was years ago. DGG 04:16, 30 September 2006 (UTC)[reply]

I think CAS naming is less important than it used to be, but probably still worth an article. I would be against putting it here, though, just because having two similar-but-different systems described on the same page may confuse the reader. Also, there are thousands of college or A-level students struggling their way through IUPAC names coming here for help on their homeworks, whereas CAS naming is only used by a much more limited group of people. Walkerma 15:26, 30 September 2006 (UTC)[reply]

Possibly the language used may be a UK/US difference? But agreed, it isn't as important as when you had to learn it by heart in order to effectively search Chemical Abstracts. I see we already have a chemical nomenclature category, and it isnt high on my priority list either. DGG 05:02, 1 October 2006 (UTC)[reply]

It is very difficult to write good articles on these subjects. CAS names are interesting because they are supposedly unique (that's the idea, anyway) whereas IUPAC ditched the goal of uniqueness to keep the system simpler. This story should be told somewhere on Wikipedia, but I'm never quite sure where. Physchim62 (talk) 14:37, 5 October 2006 (UTC)[reply]

perhaps the article on chemical nomenclature, , then the specifics on a page for each. DGG 18:49, 5 October 2006 (UTC)[reply]

Regarding the table in the Alkanes section[edit]

Can an organic compound have more than 20 carbon atoms ? If so, the table would need to be extended. MP (talk) 07:26, 14 October 2006 (UTC)[reply]

An organic compound can indeed have more than 20 carbons (or more than 1000) and I have added the system for naming carbon-chains up to 100 carbons. You won't need those names very often though. I know the table doesn't look very nice but I don't know how to make it look better. I hope some one will fix that.130.225.245.182 20:48, 13 November 2006 (UTC)[reply]

The page here is about all IUPAC nomenclature. We don't need and shouldn't try to have full details about every specific class here--many of them already have their own pages that go into fuller detail. The alkane section already begins with "Main article: Alkanes", taking one to a pages explains the chain-length rules in more detail, and from there further linking to IUPAC numerical multiplier for the more complete and gory details. So I replaced your "more but still not all lengths" table here with a link to that comprehensive list. DMacks 20:56, 13 November 2006 (UTC)[reply]

Acyl Chlorides[edit]

I didn't see any mention of acid chlorides or acid anhydrides as carboxylic acid derivatives. Inclusion would be helpful.71.215.136.243 21:35, 10 June 2007 (UTC)71.215.136.243 00:36, 11 June 2007 (UTC)[reply]

Error in image[edit]

I've removed the following comment from the article: (The structure shown in the image at the left is incorrect.) Indeed, the image Image:Iupac-amine.png is inconsistent with the text that states "the substituent groups are ordered alphabetically". -- Ed (Edgar181) 16:11, 22 January 2008 (UTC)[reply]

A corrected image was provided by Fvasconcellos (Project Wikipedia:Graphic_Lab/Images_to_improve#Vectoring_images_for_IUPAC_nomenclature). --Ondrejsv (talk) 18:13, 22 January 2008 (UTC)[reply]

Fantastic. Shouldn't all the .svg images be added in place of the .pngs, then? -- Ed (Edgar181) 18:53, 22 January 2008 (UTC)[reply]

I've gone ahead and replaced them all with the new .svg files. -- Ed (Edgar181) 19:43, 22 January 2008 (UTC)[reply]

Yes, they should. Thanks, Ed. --Ondrejsv (talk) 14:28, 23 January 2008 (UTC)[reply]

Merger proposal[edit]

I propose that all the prefix/suffix organic chemistry pages be merged to this page. Most of the information covered by these articles, does or should belong here. Also I see little reason for these articles to be expanded much more than their current state. - Jkasd (talk) 18:12, 28 March 2008 (UTC)[reply]
Disagree, with big big articles in practice it will be impossible to find the prefix you are looking for. If a reader is looking for the meaning of nor- give that reader what he or she is looking for and do not present a big big article. V8rik (talk) 19:38, 28 March 2008 (UTC)[reply]
Do not merge. To template Template:Orgchemsuffixes I added a link "For more information, see IUPAC nomenclature of organic chemistry." Anthony Appleyard (talk) 22:15, 28 March 2008 (UTC)[reply]
I read your comments, V8rik, on your user page about merging and stubs, and now I can see that even small pages like these can be useful. Since it looks like these articles are going to be kept, I think we shoud add something about functional groups to them, maybe link them to all the relevant pages. (By the way, the Organic Chemistry Affixes at the top of the template Template:Orgchemsuffixes already links to this page. It should probably be renamed to something more obvious though.) Jkasd (talk) 16:10, 29 March 2008 (UTC)[reply]

Table added[edit]

I added a table of the overview of most functional groups. Please add the remaining groups. Thanks, ManishEarth ^Talk 10:42, 6 August 2008 (UTC)[reply]

Basic principles changed[edit]

I have changed the section Basic principles by giving an outline of steps to follow to name a compound. I have also added an example with a fictitious molecule, and gone through the steps of naming it. This molecule may or may not exist in the free state, but it has almost all the aspects of a hydrocarbon, with multiple functional groups, multiple side chains, and all three types of covalent bonds ManishEarth ^Talk 09:45, 8 August 2008 (UTC)[reply]

I think this is a good start but it needs editing for conciseness. Also start with an easier example. The molecule is way to big to tell what's going on where. I also didn't see any notes on the precedence of the weight of halogens nor on the classification of Alkyl branches. I think overall the outline may be hard to understand from a layman's point of view. It seems like the reader would be better served if the outline were at the end of the article.Elleacampbell (talk) 16:42, 13 October 2008 (UTC)[reply]

The sample molecule shows almost all the aspects of naming, an can clarify some conflicts. Through this molecule, we can go through all the steps of naming. ManishEarth ^Talk 08:56, 16 October 2008 (UTC)[reply]

I am, indeed, Elleacampbe's layman coming to this article for the first time: I got an A in GCSE chemistry but that is the extent of my expertise. I would like to congratulate Manish on his (super-human) attempt to explain the basic principles, but I do have a problem with certain parts which are not clearly explained and with certain terms not clearly defined (if at all). Not being an Organic Chemist, I am assuming there are no flaws in his steps aside from logical or linguistic errors. I will comment each step as outlined and numbered in the article.

1. Identify the parent... Well explained: no problem.

2. Identify the functional group... Despite there being a link to functional group in the preamble, we could do with a concise definition here like we have in the first step. This will save time for readers that just want the basics. (In fact I missed the link when I was reading the article since I jumped straight to the steps.)

Done I added a wikilink. There is no need of writing a definition, as Wikipedia is all about interlinks.ManishEarth^{Talk • Stalk} 08:47, 5 March 2009 (UTC)[reply]

2.1. Identify the position... Position where, in what, with respect to what? I assume you mean ...in the chain, but you could equally mean ...in the formula or any number of other things.

DoneManishEarth^{Talk • Stalk} 08:47, 5 March 2009 (UTC)[reply]

2.2. ...The functional group should have the lower number (as there are two ways of numbering—right to left and left to right)... I have tried to understand what this means for about an hour without looking it up. I don't understand what this means at all. (a) Do you mean ...should end up with... or ...should be given... or ...should already have...? (b) The lower number than which other entity's number? (c) Which numbering system should you actually use, therefore? [Incidentally, how come there isn't a consensus to use a particular numbering system? Surely it would make life a lot easier?!] Basically, this entire sub-step needs to be elucidated for the lay reader.

DoneManishEarth^{Talk • Stalk} 08:47, 5 March 2009 (UTC)[reply]

2.2. ...The number is written before the name of the functional group suffix (such as -ol, -one, -al, etc.)... This is clearly not correct: the numbers come before the group name not the suffix. 2,5,5-trimethylhexane not trimethylhex-2,5,5-ane. [Or perhaps you mean they come before that part of the the name that ends with the suffix?]

Strictly speaking, This line is correct. Though you can say 2-pentanol, the correct way is to say pentan-2-ol, just like 2-butene is correctly written as but-2-ene.ManishEarth^{Talk • Stalk} 08:47, 5 March 2009 (UTC)[reply]

2.2. ...If the group is a terminal-only group, that can only be at the end of a chain... Is the latter part of this a definition of terminal-only group or a type of terminal-only group? If you mean the first, the definition should read something like ...ie a group that can only be at the end of a chain...; if you mean the second, that term needs defining and the statement as it stands changed to ...of the type that can only be at the end of a chain....

DoneManishEarth^{Talk • Stalk} 08:47, 5 March 2009 (UTC)[reply]

2.2. Note ...The end result ... Of what? Numbering in both directions, merely ends up which two sets of numbers, which I still have no obvious use for. "Finding" side-chains doesn't help as there are still two numbers to be prioritized in some unexplained manner. (Sorry to be brutal!)

DoneManishEarth^{Talk • Stalk} 08:47, 5 March 2009 (UTC)[reply]

3. Identify the side-chains and number them. Side chains should probably defined here rather than in the note to 2.2., since this is the step where they are actually considered.

DoneManishEarth^{Talk • Stalk} 09:00, 5 March 2009 (UTC)[reply]

3.1. If there are more than one of the same type... English Usage: If there is more than one of the same type. The object is type which is singular. (Sorry for the pedantry!)

DoneManishEarth^{Talk • Stalk} 09:00, 5 March 2009 (UTC)[reply]

3.1. ...The numbers...will be grouped... Do we group them all as a lump irrespective of which group they come from or with each group one after the other, ie 1,2,2,3,3,4-Tri... or 2,3,2,1,3,4-Tri...?

Umm... I wrote 'for that type of side chain', so each side chain has its own set of numbers and is placed seperately.ManishEarth^{Talk • Stalk} 09:00, 5 March 2009 (UTC)[reply]

3.2 Different side-chains... Well explained, but needs to be more concise. Perhaps the examples could be slightly expanded and take the form ie amino-, ammonio-, tricarboxy-, ethyl-, dimethyl-... etc not amino-, ammonio-, dimethyl-, ethyl-, tricarboxy- ... etc. When you do that ...as the "e" in "ethyl...[etc]" will then become redundant, I suspect, as the reader should follow the logic well enough.