Science desk
< January 15	<< Dec \| January \| Feb >>	Current desk >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is a transcluded archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

January 16[edit]

What is MN and NE in Canada?[edit]

In the article Carex rosea, you can read: "In Canada, C. rosea is distributed from Nova Scotia and southern Quebec west to MN and eastern NE". What is MN and NE in Canada? Dipsacus fullonum (talk) 12:46, 16 January 2023 (UTC)[reply]

The US states of Minnesota and Nebraska — the website used as the source consistently uses postal abbreviations for US states. Expanded per MOS:POSTABBR. –LaundryPizza03 (d c̄) 13:15, 16 January 2023 (UTC)[reply]

It used to not always be clear if a 2-letter postal abbreviation was USA or Canada but at least officially they changed enough of the offending ones to end all overlap. I've always wondered what's the closest state/province/territory equivalent to CONUS with the same official mail code as one in the intentional non-collision zone. Sagittarian Milky Way (talk) 15:10, 16 January 2023 (UTC)[reply]

Thank you for help and updating the obscure text. --Dipsacus fullonum (talk) 16:53, 16 January 2023 (UTC)[reply]

US and Canadian postal abbreviations for their respective states/provinces/territories are intentionally harmonized to avoid conflicts between the two countries. See Canadian postal abbreviations for provinces and territories; where it notes the intentional practice. --Jayron 32 19:19, 17 January 2023 (UTC)[reply]

And also says Nebraska switched from NB to NE in November 1969 so New Brunswick wouldn't have to share. It also answers my wonder: Baja, Coahuila and New Lion are zero miles from CONUS and have 2-letter codes BC, CO and NL but Mexico doesn't even have official 2-letter postcodes. Sagittarian Milky Way (talk) 20:15, 17 January 2023 (UTC)[reply]

See Template:Mexico State-Abbreviation Codes for some of the options...Naraht (talk) 21:08, 17 January 2023 (UTC)[reply]

Formation of hexachlorophosphazene[edit]

At the article Hexachlorophosphazene, I noticed a clarification template (and yet another improperly formatted reason) attached to an unbalanced chemical reaction, which is part of the hypothesized polymerization mechanism:

NH₃ + [PCl₄]⁺ → "HN=PCl₃" + HCl

(1)

There is a missing H and a loss of +1 charge unit on the right-hand side, and no explanation for the scare quotes on the complex molecule (a hypothetical phosphine imide intermediate), so I assumed that the correct reaction is one of the following, which are likely equally valid due to the nucleophile property of imides:

NH₃ + [PCl₄]⁺ → HN=PCl₃ + HCl + H⁺

(2a)

NH₃ + [PCl₄]⁺ → [H₂N−PCl₃]⁺ + HCl

(2b)

In the article, I used Eq. 2a for continuity with te later steps, but I need someone to double-check Greenwood & Earnshaw, 2nd edition (the source that was used in this section) or other scientific literature on this topic to confirm that the correct equation is not something else entirely. –LaundryPizza03 (d c̄) 13:12, 16 January 2023 (UTC)[reply]

For specific reference requests ("page XXX of Greenwood and Earnshaw"), WP:RX is the magic place. RX also handles general requests, but the odds that any of them has the sufficient expertise in chemistry are slim. (Those odds increase a bit on RD/S, but are still low.) Tigraan^{Click here for my talk page ("private" contact)} 15:22, 16 January 2023 (UTC)[reply]

The book can be previewed at Google Books, but appears not to contain the term "hexachlorophosphazene". I think, though, this passage on page 537 in §12.3.7, Phosphorus–nitrogen compounds, is relevant:

Many details of the preparative reaction mechanism remain unclear but it is thought that NH₄Cl partly dissociates into NH₃ and HCl, and that PCl₅ reacts in its ionic form PCl₄⁺PCl₆⁻ (p. 499). Nucleophilic attack by NH₃ on PCl₄⁺ then occurs with elimination of HCl and the {HN=PCl₃} attacks a second PCl₄⁺ to give [Cl₃P=N–PCl₃]⁺ and HCl. After 1 h the major (insoluble) intermediate product is [Cl₃P=N–PCl₃]⁺PCl₆⁻ (i.e. P₃NCl₁₂, p. 536) and this then slowly reacts with more NH₃ to give HCl and {Cl₃P=N–PCl₂=NH}, etc. ^[1]

--Lambiam 15:48, 16 January 2023 (UTC)[reply]

Thanks, this was exactly the same as the presentation in the article, except for one additional minor error. –LaundryPizza03 (d c̄) 05:32, 17 January 2023 (UTC)[reply]

As doi:10.1055/sos-SD-042-01089 points out, hexachlorophosphazene is normally produced from ammonium chloride and PCl₅ (and the Greenwood & Earnshaw book agrees, as above). This is because the direct reaction with ammonia and PCl₅ is too exothermic to control easily. We arrow-pushers are no doubt over-simplifying no matter how we write the individual steps. For example, the diagram below is taken from our article on phosphorus pentachloride for its reaction with a carboxylic acid, cited to a standard organic text book.

There's no hint of PCl₄⁺ there and the mechanism as drawn is clearly over-complex as it could have shown the chloride ion attacking the carbonyl group immediately in the second step, rather than 3 steps later! The point I'm making is that any precisely drawn mechanism for these sorts of reactions is likely fictional and what matters most is the overall outcome. Hence for the OP's question, I'd stick to writing the balanced equation:

3 NH₄Cl + 3 PCl₅ → hexachlorophosphazene + 12 HCl

Mike Turnbull (talk) 12:52, 18 January 2023 (UTC)[reply]

I suspect there's some mis-printed arrows in there. I think steps 2-3-4 are meant to be separated by double headed arrows, meant to show a chemical equilibrium. I suspect the H+ ion from the HCl is vital in stabilizing the unstable intermediate, at least enough to allow the Cl- ion to attack to the carbonyl. That's how I would read that. Otherwise, steps 3-4 are entirely superfluous. --Jayron 32 18:43, 18 January 2023 (UTC)[reply]