Talk:Spiro compound

PCP?
The structure of PCP is shown and is given as an example of a spiro compound but a) it is tricyclic and b) none of the rings share a carbon. IANAC (I Am Not A Chemist) but surely this is a red herring and should be removed? Daen 03:21, 25 March 2007 (UTC)


 * Hi Daen, thanks for spotting the error, I have removed PCP as a spiro compound. Your chemistry degree is well deserved.... — Preceding unsigned comment added by V8rik (talk • contribs) 20:43, 25 March 2007‎ (UTC)

Moving ridiculously overlong and off-subject section here for review
The following overlong material is moved here, for discussion, rather than leaving it in to spoil the article. Note, this is justified, both by its imbalance, and by its violating WP:VERIFY and WP:OR, and by its essay nature. " Correctspironumbering.png When naming polyspiro compounds, the prefixes di-, tri-, tetra-, etc. are first added to the front of the name to indicate the amount of spiroatoms, the single atoms between each ring. The atoms of the compound are numbered systematically. A polyspiro compound is numbered starting from a ring that holds one connecting spiroatom to another ring, i.e. a terminal ring; there can be two or more terminal rings to a polyspiro compound, so long as each of these rings has only one connecting spiroatom. In the terminal ring chosen to start the numbering, an atom of the ring next, and connected to the spiroatom, is labeled 1. Each following atom is numbered one higher than the previous—going around the compound.

Of the two or more terminal rings of any polyspiro compound, the terminal ring to start the numbering is chosen in such a way that the first spiroatom to be numbered, after numbering every other atom within the chosen ring, is the lowest possible number that can be assigned to a spiroatom. For example, suppose there is a compound where there are two terminal rings, 6 atoms in one ring, and 8 in another. The 6-atom ring is chosen to start the numbering, because after each other atom within the ring is numbered, the spiroatom is numbered 6, whereas the spiroatom of the 8-atom ring would be numbered 8. The direction of the numbering is determined by the following spiroatom (after the first numbered spiroatom of that terminal ring has been numbered/passed). If the following spiroatom in one direction assigned a number that is lower than the number it would be assigned in the opposite direction, then the direction of numbering that assigns the next spiroatom the lowest number is picked. The magnitude of the rest of the numbers given to the rest of the spiroatoms in the compound is irrelevant.

In some cases the first two, three, four, or more numbers that are assigned the same spiroatoms, in either numbering direction are the same. The first numbering direction to assign a particular spiroatom a lower number than the opposite direction assigns this spiroatom, is chosen. For example if a numbering system in one direction, for each spiroatom, is 3, 5, 7, 10; and for another direction the numbers of the spiroatoms are 3, 5, 7, 9, then the second mentioned numbering is chosen. In this case, in the first numbering direction there would be two atoms between the spiroatoms 7 and 10, and in the opposite numbering direction, there would be one atom between spiroatoms 7 and 9. The magnitude of any following spiroatom numbers, after the fourth one mentioned (numbered 9 in the first direction) in this case is irrelevant.

Bluespironumbering.png|thumb|left|tetraspiro[2.0.0.0.26.15.14.13]undecane In polyspiro nomenclature the first number within the brackets is the amount of atoms starting from the atom numbered 1 to the last atom on the first ring before the first numbered spiroatom. The rest of the numbers represent the amount of atoms between the spiroatoms, or the amount of atoms at a terminal ring, going in the direction of the numbering. Each number is separated by a period. In the example to the left there are two atoms (numbered 1 and 2) before the first spiroatom (3). Between spiroatoms 3 and 4 there are zero, and likewise between 5 and 4, and 6 and 5. At the second terminal ring there are two; there is one between 6 and 5, 5 and 4, and 4 and 3. This gives the sequence [2.0.0.0.2.1.1.1]. The total number of atoms determines the acyclic alkane name that follows, in this case, undecane. For clarity, superscripts of the spiroatom numbers appear after the number of atoms that are the last to encounter the spiroatom, going in the direction of the numbering.

In the example to the right, there are two spiroatoms, so the name starts with dispiro-. In the first terminal ring, there are two atoms, showing so far the name dispiro[2. Between the next two spiroatoms there is one atom, and four at the other terminal ring, revealing the name dispiro[2.1.35. The superscript for the second spiroatom, numbered 5, was added as this is the last time it will be encountered after the three atoms at the terminal ring, following the path of numbered atoms. After adding atoms 9 and 10 between spiroatoms 3 and 5, then adding the name of the alkane that has the same amount of atoms as this spiro compound, decane, the name dispiro[2.1.35.23]decane is revealed. The superscript for spiroatom 3 is added after the atoms 9 and 10 are represented (by a 2) since after these two atoms are encountered the spiroatom 3 is encountered for the last time."

Please move a summary sentence of two back into the article, in the process of making the remainder of the section a good paragraph on polypro compounds. Please add no sentences without sources. Thank you. Le Prof Leprof 7272 (talk) 03:02, 3 February 2016 (UTC)

Leaving reasonable unsourced text in place, and leaving "unreferenced" tag
…at least until the lede is fully sourced, and some progress is made on the rest of the article. (Only the dated von Baeyer citation was present when that tag was placed. The Clayden, chemspider, Smith & Baxendale, and SciNews are new to this editing.) Cheers. Le Prof Leprof 7272 (talk) 23:14, 3 February 2016 (UTC)
 * Downgraded the "unreferenced" tag to "refimprove" today, with addition of more sources to the lede.
 * Le Prof Leprof 7272 (talk) 05:26, 4 February 2016 (UTC)

Merger proposal
Please discuss the proposed merge of the stub Spiroaromaticity as a section into this article.
 * Support. The Spiroaromaticity article is currently two sentences, and wholly unsourced. Though it might eventually find interest to give it substance, the area of aromaticity, and this very narrow niche subject of spiroaromaticity (a physical organic chemistry subject, mostly), is best served as a solid paragraph in an article on spiro compounds in general—(1) so the structures already appearing in spiro can be used as reference, and (2) so general concepts of orthgonality of rings needn't be redundantly explained—with a cross reference and summary in the aromaticity article. It in no way requires a separate article, and the added burden to maintain it with quality. (Two places only, spiro and aromaticity, and not the third, "sprioaromaticity"!) Bottom line, better the expert physical organic set of eyes all in one place, making one article and its cross-references good, than split between too many small articles. We need the writing of such experts focused, and here, adding flavour and expertise (and we need them badly). Le Prof Leprof 7272 (talk) 05:26, 4 February 2016 (UTC)
 * Agreed and ✅ Klbrain (talk) 18:23, 27 December 2017 (UTC)

Recent edits
These have focused on making the lede correct, and sourced. The result has been that the lede is temporarily long. This is the consequence of the process: I simply took the structure of the lede as I found it, correcting all the mistaken statements, adding (1) solid, reliable sources, and (2) any glaring factual omissions of which I was immediately aware (quaternary N as spiro atom, three types not one of chirality, spirane as synonym, etc.).

There are clear shortcomings in such a detailed lede; I am aware of these, but ask patience: Please do not remove material and sources in the lede, until they have been used to correct and to begin to expand the main body's text. In short, the rest of the article is under/unsourced, is poorly structured, lacking content it should have, etc. I has to be brought into line with the lede, and so for now the lede is a source of material for the main body. Note also, as the tag of the article says, now there are discrepant statements between the lede and main body. It is the lede that is both (largely) sourced and correct. Cheers, Le Prof Leprof 7272 (talk) 00:35, 11 February 2016 (UTC)
 * Hear hear! Do not 'remove'.... 'improve'!
 * Simon de Danser (talk) 16:33, 12 September 2017 (UTC)