Dicyanoacetylene

{{chembox

| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 430784049

| Name = Dicyanoacetylene

| ImageFile = Dicyanoacetylene Structural Formula V2.svg

| ImageFile1 = Dicyanoacetylene-3D-balls.png

| ImageFile2 = Dicyanoacetylene-3D-vdW.png

| PIN = But-2-ynedinitrile

| OtherNames = {{ubl|Acetylenedicarbonitrile|Butynedinitrile|Carbon subnitride|Dicyanoacetylene}}

|Section1={{Chembox Identifiers

| CASNo_Ref = {{cascite|changed|}}

| CASNo = 1071-98-3

| PubChem = 14068

| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}

| ChemSpiderID = 13449

| SMILES = N#CC#CC#N

| InChI = 1/C4N2/c5-3-1-2-4-6

| InChIKey = ZEHZNAXXOOYTJM-UHFFFAOYAR

| StdInChI_Ref = {{stdinchicite|changed|chemspider}}

| StdInChI = 1S/C4N2/c5-3-1-2-4-6

| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}

| StdInChIKey = ZEHZNAXXOOYTJM-UHFFFAOYSA-N

}}

|Section2={{Chembox Properties

| C = 4

| N = 2

| Appearance = Colorless volatile liquid

| Odor = Strong

| Density = 0.907 g/cm³

| MeltingPtC = 20.5

| BoilingPtC = 76.5

| SolubleOther = Soluble in organic solvents

}}

|Section4={{Chembox Thermochemistry

| DeltaHf = +500.4 kJ/mol

| HeatCapacity = 77.6017 J/(mol·K)

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| Section7 = {{Chembox Hazards

| AutoignitionPt =

| ExploLimits =

| FlashPt =

| LD50 =

| LC50 =

| MainHazards = Very flammable. Explosive.

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|Section8={{Chembox Related

| OtherCompounds = {{ubl|Carbon suboxide|Cyanogen|Cyanoacetylene}}

}}

Dicyanoacetylene, also called carbon subnitride or but-2-ynedinitrile (IUPAC), is a compound of carbon and nitrogen with chemical formula {{chem2|C4N2}}. At room temperature, dicyanoacetylene is a colorless volatile liquid. It has a linear molecular structure, {{chem2|N\tC\sC\tC\sC\tN}} (often abbreviated as {{chem2|NC4N}}), with alternating triple and single covalent bonds. It can be viewed as acetylene with the two hydrogen atoms replaced by cyanide groups.

Because of its high endothermic heat of formation, dicyanoacetylene can explode to carbon powder and nitrogen gas,

:{{chem2|C4N2 → 4 C + N2}}

and it burns in oxygen with a bright blue-white flame at a temperature of {{convert|5260|K}}, the hottest flame in oxygen; burned in ozone at high pressure the flame temperature exceeds {{convert|6000|K}}.{{cite journal |author1=Kirshenbaum, A. D. |author2=Grosse, A. V. | year = 1956 | title = The Combustion of Carbon Subnitride, C4N2, and a Chemical Method for the Production of Continuous Temperatures in the Range of 5000–6000K | journal = Journal of the American Chemical Society | volume = 78 | issue = 9 | pages = 2020 | doi = 10.1021/ja01590a075}} Dicyanoacetylene polymerizes at room temperature into a dark solid.https://pubs.acs.org/doi/10.1021/jo01266a014 Syntheses of dicyanoacetylene, Engelbert Ciganek, and Carl G. Krespan, J. Org. Chem., 1968, 33 (2), pp 541–544

Synthesis

Dicyanoacetylene can be prepared by passing nitrogen gas over a sample of graphite heated to temperatures between {{cvt|2673 and 3000|K|C F}}.{{cite journal |author1=Ciganek, E. |author2=Krespan, C. G. | title = Syntheses of Dicyanoacetylene | journal = The Journal of Organic Chemistry |year = 1968 | volume = 33 | issue = 2 | pages = 541–544 | doi = 10.1021/jo01266a014}} It may also be synthesized via a reaction between a dihaloacetylene and a cyanide salt:{{Citation needed|date=March 2024}}

:{{chem2|X\sC\tC\sX + 2 MCN → N\tC\sC\tC\sC\tN + 2 MX}}

As a reagent in organic chemistry

Dicyanoacetylene is a powerful dienophile because the cyanide groups are electron-withdrawing, so it is a useful reagent for Diels–Alder reactions with unreactive dienes. It even adds to the aromatic compound durene (1,2,4,5-tetramethylbenzene) to form a substituted bicyclooctatriene.{{cite journal | author = Weis, C. D. | year = 1963 | title = Reactions of Dicyanoacetylene | journal = Journal of Organic Chemistry | volume = 28 | issue = 1 | pages = 74–78 | doi = 10.1021/jo01036a015}} Only the most reactive of dienophiles can attack such aromatic compounds.

In outer space

Solid dicyanoacetylene has been detected in the atmosphere of Titan by infrared spectroscopy.{{cite journal |author1=Samuelson, R. E. |author2=Mayo, L. A. |author3=Knuckles, M. A. |author4=Khanna, R. J. | year = 1997 | title = C₄N₂ Ice in Titan's North Polar Stratosphere | journal = Planetary and Space Science | volume = 45 | issue = 8 | pages = 941–948 | doi = 10.1016/S0032-0633(97)00088-3 | bibcode = 1997P&SS...45..941S}} As the seasons change on Titan, the compound condenses and evaporates in a cycle, which allows scientists on Earth to study Titanian meteorology.

{{As of|2006}}, the detection of dicyanoacetylene in the interstellar medium has been impossible, because its symmetry means it has no rotational microwave spectrum. However, similar asymmetric molecules like cyanoacetylene have been observed, and its presence in those environments is therefore suspected.{{cite journal | author = Kołos, R. | year = 2002 | title = Exotic Isomers of Dicyanoacetylene: A Density Functional Theory and ab initio Study | journal = Journal of Chemical Physics | volume = 117 | issue = 5 | pages = 2063–2067 | doi = 10.1063/1.1489992 |bibcode = 2002JChPh.117.2063K |url=https://zenodo.org/record/1000211}}

References

Category:Conjugated nitriles

Category:Alkyne derivatives

Dicyanoacetylene

Synthesis

As a reagent in organic chemistry

In outer space

See also

References